The macros NULL_DEV and DEVNULL were both used to work around

[PostgreSQL.git] / src / backend / postmaster / postmaster.c

/*-------------------------------------------------------------------------
 *
 * postmaster.c
 *        This program acts as a clearing house for requests to the
 *        POSTGRES system.      Frontend programs send a startup message
 *        to the Postmaster and the postmaster uses the info in the
 *        message to setup a backend process.
 *
 *        The postmaster also manages system-wide operations such as
 *        startup and shutdown. The postmaster itself doesn't do those
 *        operations, mind you --- it just forks off a subprocess to do them
 *        at the right times.  It also takes care of resetting the system
 *        if a backend crashes.
 *
 *        The postmaster process creates the shared memory and semaphore
 *        pools during startup, but as a rule does not touch them itself.
 *        In particular, it is not a member of the PGPROC array of backends
 *        and so it cannot participate in lock-manager operations.      Keeping
 *        the postmaster away from shared memory operations makes it simpler
 *        and more reliable.  The postmaster is almost always able to recover
 *        from crashes of individual backends by resetting shared memory;
 *        if it did much with shared memory then it would be prone to crashing
 *        along with the backends.
 *
 *        When a request message is received, we now fork() immediately.
 *        The child process performs authentication of the request, and
 *        then becomes a backend if successful.  This allows the auth code
 *        to be written in a simple single-threaded style (as opposed to the
 *        crufty "poor man's multitasking" code that used to be needed).
 *        More importantly, it ensures that blockages in non-multithreaded
 *        libraries like SSL or PAM cannot cause denial of service to other
 *        clients.
 *
 *
 * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *        $PostgreSQL$
 *
 * NOTES
 *
 * Initialization:
 *              The Postmaster sets up shared memory data structures
 *              for the backends.
 *
 * Synchronization:
 *              The Postmaster shares memory with the backends but should avoid
 *              touching shared memory, so as not to become stuck if a crashing
 *              backend screws up locks or shared memory.  Likewise, the Postmaster
 *              should never block on messages from frontend clients.
 *
 * Garbage Collection:
 *              The Postmaster cleans up after backends if they have an emergency
 *              exit and/or core dump.
 *
 * Error Reporting:
 *              Use write_stderr() only for reporting "interactive" errors
 *              (essentially, bogus arguments on the command line).  Once the
 *              postmaster is launched, use ereport().  In particular, don't use
 *              write_stderr() for anything that occurs after pmdaemonize.
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include <unistd.h>
#include <signal.h>
#include <time.h>
#include <sys/wait.h>
#include <ctype.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <fcntl.h>
#include <sys/param.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <limits.h>

#ifdef HAVE_SYS_SELECT_H
#include <sys/select.h>
#endif

#ifdef HAVE_GETOPT_H
#include <getopt.h>
#endif

#ifdef USE_BONJOUR
#include <DNSServiceDiscovery/DNSServiceDiscovery.h>
#endif

#include "access/transam.h"
#include "access/xlog.h"
#include "bootstrap/bootstrap.h"
#include "catalog/pg_control.h"
#include "lib/dllist.h"
#include "libpq/auth.h"
#include "libpq/ip.h"
#include "libpq/libpq.h"
#include "libpq/pqsignal.h"
#include "miscadmin.h"
#include "pgstat.h"
#include "postmaster/autovacuum.h"
#include "postmaster/fork_process.h"
#include "postmaster/pgarch.h"
#include "postmaster/postmaster.h"
#include "postmaster/syslogger.h"
#include "storage/fd.h"
#include "storage/ipc.h"
#include "storage/pg_shmem.h"
#include "storage/pmsignal.h"
#include "storage/proc.h"
#include "tcop/tcopprot.h"
#include "utils/builtins.h"
#include "utils/datetime.h"
#include "utils/memutils.h"
#include "utils/ps_status.h"

#ifdef EXEC_BACKEND
#include "storage/spin.h"
#endif


/*
 * List of active backends (or child processes anyway; we don't actually
 * know whether a given child has become a backend or is still in the
 * authorization phase).  This is used mainly to keep track of how many
 * children we have and send them appropriate signals when necessary.
 *
 * "Special" children such as the startup, bgwriter and autovacuum launcher
 * tasks are not in this list.  Autovacuum worker processes are in it.
 * Also, "dead_end" children are in it: these are children launched just
 * for the purpose of sending a friendly rejection message to a would-be
 * client.      We must track them because they are attached to shared memory,
 * but we know they will never become live backends.
 */
typedef struct bkend
{
        pid_t           pid;                    /* process id of backend */
        long            cancel_key;             /* cancel key for cancels for this backend */
        bool            is_autovacuum;  /* is it an autovacuum process? */
        bool            dead_end;               /* is it going to send an error and quit? */
} Backend;

static Dllist *BackendList;

#ifdef EXEC_BACKEND
/*
 * Number of entries in the shared-memory backend table.  This table is used
 * only for sending cancels, and therefore only includes children we allow
 * cancels on: regular backends and autovac workers.  In particular we exclude
 * dead_end children, allowing the table to have a known maximum size, to wit
 * the same too-many-children limit enforced by canAcceptConnections().
 */
#define NUM_BACKENDARRAY_ELEMS (2*MaxBackends)

static Backend *ShmemBackendArray;
#endif

/* The socket number we are listening for connections on */
int                     PostPortNumber;
char       *UnixSocketDir;
char       *ListenAddresses;

/*
 * ReservedBackends is the number of backends reserved for superuser use.
 * This number is taken out of the pool size given by MaxBackends so
 * number of backend slots available to non-superusers is
 * (MaxBackends - ReservedBackends).  Note what this really means is
 * "if there are <= ReservedBackends connections available, only superusers
 * can make new connections" --- pre-existing superuser connections don't
 * count against the limit.
 */
int                     ReservedBackends;

/* The socket(s) we're listening to. */
#define MAXLISTEN       64
static int      ListenSocket[MAXLISTEN];

/*
 * Set by the -o option
 */
static char ExtraOptions[MAXPGPATH];

/*
 * These globals control the behavior of the postmaster in case some
 * backend dumps core.  Normally, it kills all peers of the dead backend
 * and reinitializes shared memory.  By specifying -s or -n, we can have
 * the postmaster stop (rather than kill) peers and not reinitialize
 * shared data structures.      (Reinit is currently dead code, though.)
 */
static bool Reinit = true;
static int      SendStop = false;

/* still more option variables */
bool            EnableSSL = false;
bool            SilentMode = false; /* silent mode (-S) */

int                     PreAuthDelay = 0;
int                     AuthenticationTimeout = 60;

bool            log_hostname;           /* for ps display and logging */
bool            Log_connections = false;
bool            Db_user_namespace = false;

char       *bonjour_name;

/* PIDs of special child processes; 0 when not running */
static pid_t StartupPID = 0,
                        BgWriterPID = 0,
                        WalWriterPID = 0,
                        AutoVacPID = 0,
                        PgArchPID = 0,
                        PgStatPID = 0,
                        SysLoggerPID = 0;

/* Startup/shutdown state */
#define                 NoShutdown              0
#define                 SmartShutdown   1
#define                 FastShutdown    2

static int      Shutdown = NoShutdown;

static bool FatalError = false; /* T if recovering from backend crash */

/*
 * We use a simple state machine to control startup, shutdown, and
 * crash recovery (which is rather like shutdown followed by startup).
 *
 * Normal child backends can only be launched when we are in PM_RUN state.
 * (We also allow it in PM_WAIT_BACKUP state, but only for superusers.)
 * In other states we handle connection requests by launching "dead_end"
 * child processes, which will simply send the client an error message and
 * quit.  (We track these in the BackendList so that we can know when they
 * are all gone; this is important because they're still connected to shared
 * memory, and would interfere with an attempt to destroy the shmem segment,
 * possibly leading to SHMALL failure when we try to make a new one.)
 * In PM_WAIT_DEAD_END state we are waiting for all the dead_end children
 * to drain out of the system, and therefore stop accepting connection
 * requests at all until the last existing child has quit (which hopefully
 * will not be very long).
 *
 * Notice that this state variable does not distinguish *why* we entered
 * states later than PM_RUN --- Shutdown and FatalError must be consulted
 * to find that out.  FatalError is never true in PM_RUN state, nor in
 * PM_SHUTDOWN states (because we don't enter those states when trying to
 * recover from a crash).  It can be true in PM_STARTUP state, because we
 * don't clear it until we've successfully recovered.
 */
typedef enum
{
        PM_INIT,                                        /* postmaster starting */
        PM_STARTUP,                                     /* waiting for startup subprocess */
        PM_RUN,                                         /* normal "database is alive" state */
        PM_WAIT_BACKUP,                         /* waiting for online backup mode to end */
        PM_WAIT_BACKENDS,                       /* waiting for live backends to exit */
        PM_SHUTDOWN,                            /* waiting for bgwriter to do shutdown ckpt */
        PM_SHUTDOWN_2,                          /* waiting for archiver to finish */
        PM_WAIT_DEAD_END,                       /* waiting for dead_end children to exit */
        PM_NO_CHILDREN                          /* all important children have exited */
} PMState;

static PMState pmState = PM_INIT;

bool            ClientAuthInProgress = false;           /* T during new-client
                                                                                                 * authentication */

bool            redirection_done = false;       /* stderr redirected for syslogger? */

/* received START_AUTOVAC_LAUNCHER signal */
static volatile sig_atomic_t start_autovac_launcher = false;

/*
 * State for assigning random salts and cancel keys.
 * Also, the global MyCancelKey passes the cancel key assigned to a given
 * backend from the postmaster to that backend (via fork).
 */
static unsigned int random_seed = 0;
static struct timeval random_start_time;

extern char *optarg;
extern int      optind,
                        opterr;

#ifdef HAVE_INT_OPTRESET
extern int      optreset;
#endif

/*
 * postmaster.c - function prototypes
 */
static void checkDataDir(void);

#ifdef USE_BONJOUR
static void reg_reply(DNSServiceRegistrationReplyErrorType errorCode,
                  void *context);
#endif
static void pmdaemonize(void);
static Port *ConnCreate(int serverFd);
static void ConnFree(Port *port);
static void reset_shared(int port);
static void SIGHUP_handler(SIGNAL_ARGS);
static void pmdie(SIGNAL_ARGS);
static void reaper(SIGNAL_ARGS);
static void sigusr1_handler(SIGNAL_ARGS);
static void dummy_handler(SIGNAL_ARGS);
static void CleanupBackend(int pid, int exitstatus);
static void HandleChildCrash(int pid, int exitstatus, const char *procname);
static void LogChildExit(int lev, const char *procname,
                         int pid, int exitstatus);
static void PostmasterStateMachine(void);
static void BackendInitialize(Port *port);
static int      BackendRun(Port *port);
static void ExitPostmaster(int status);
static int      ServerLoop(void);
static int      BackendStartup(Port *port);
static int      ProcessStartupPacket(Port *port, bool SSLdone);
static void processCancelRequest(Port *port, void *pkt);
static int      initMasks(fd_set *rmask);
static void report_fork_failure_to_client(Port *port, int errnum);
static enum CAC_state canAcceptConnections(void);
static long PostmasterRandom(void);
static void RandomSalt(char *md5Salt);
static void signal_child(pid_t pid, int signal);
static void SignalSomeChildren(int signal, bool only_autovac);

#define SignalChildren(sig)                     SignalSomeChildren(sig, false)
#define SignalAutovacWorkers(sig)       SignalSomeChildren(sig, true)
static int      CountChildren(void);
static bool CreateOptsFile(int argc, char *argv[], char *fullprogname);
static pid_t StartChildProcess(AuxProcType type);
static void StartAutovacuumWorker(void);

#ifdef EXEC_BACKEND

#ifdef WIN32
static pid_t win32_waitpid(int *exitstatus);
static void WINAPI pgwin32_deadchild_callback(PVOID lpParameter, BOOLEAN TimerOrWaitFired);

static HANDLE win32ChildQueue;

typedef struct
{
        HANDLE          waitHandle;
        HANDLE          procHandle;
        DWORD           procId;
}       win32_deadchild_waitinfo;

HANDLE          PostmasterHandle;
#endif

static pid_t backend_forkexec(Port *port);
static pid_t internal_forkexec(int argc, char *argv[], Port *port);

/* Type for a socket that can be inherited to a client process */
#ifdef WIN32
typedef struct
{
        SOCKET          origsocket;             /* Original socket value, or -1 if not a
                                                                 * socket */
        WSAPROTOCOL_INFO wsainfo;
}       InheritableSocket;
#else
typedef int InheritableSocket;
#endif

typedef struct LWLock LWLock;   /* ugly kluge */

/*
 * Structure contains all variables passed to exec:ed backends
 */
typedef struct
{
        Port            port;
        InheritableSocket portsocket;
        char            DataDir[MAXPGPATH];
        int                     ListenSocket[MAXLISTEN];
        long            MyCancelKey;
        unsigned long UsedShmemSegID;
        void       *UsedShmemSegAddr;
        slock_t    *ShmemLock;
        VariableCache ShmemVariableCache;
        Backend    *ShmemBackendArray;
        LWLock     *LWLockArray;
        slock_t    *ProcStructLock;
        PROC_HDR   *ProcGlobal;
        PGPROC     *AuxiliaryProcs;
        InheritableSocket pgStatSock;
        pid_t           PostmasterPid;
        TimestampTz PgStartTime;
        TimestampTz PgReloadTime;
        bool            redirection_done;
#ifdef WIN32
        HANDLE          PostmasterHandle;
        HANDLE          initial_signal_pipe;
        HANDLE          syslogPipe[2];
#else
        int                     syslogPipe[2];
#endif
        char            my_exec_path[MAXPGPATH];
        char            pkglib_path[MAXPGPATH];
        char            ExtraOptions[MAXPGPATH];
        char            lc_collate[NAMEDATALEN];
        char            lc_ctype[NAMEDATALEN];
}       BackendParameters;

static void read_backend_variables(char *id, Port *port);
static void restore_backend_variables(BackendParameters * param, Port *port);

#ifndef WIN32
static bool save_backend_variables(BackendParameters * param, Port *port);
#else
static bool save_backend_variables(BackendParameters * param, Port *port,
                                           HANDLE childProcess, pid_t childPid);
#endif

static void ShmemBackendArrayAdd(Backend *bn);
static void ShmemBackendArrayRemove(pid_t pid);
#endif   /* EXEC_BACKEND */

#define StartupDataBase()               StartChildProcess(StartupProcess)
#define StartBackgroundWriter() StartChildProcess(BgWriterProcess)
#define StartWalWriter()                StartChildProcess(WalWriterProcess)

/* Macros to check exit status of a child process */
#define EXIT_STATUS_0(st)  ((st) == 0)
#define EXIT_STATUS_1(st)  (WIFEXITED(st) && WEXITSTATUS(st) == 1)


/*
 * Postmaster main entry point
 */
int
PostmasterMain(int argc, char *argv[])
{
        int                     opt;
        int                     status;
        char       *userDoption = NULL;
        int                     i;

        MyProcPid = PostmasterPid = getpid();

        MyStartTime = time(NULL);

        IsPostmasterEnvironment = true;

        /*
         * for security, no dir or file created can be group or other accessible
         */
        umask((mode_t) 0077);

        /*
         * Fire up essential subsystems: memory management
         */
        MemoryContextInit();

        /*
         * By default, palloc() requests in the postmaster will be allocated in
         * the PostmasterContext, which is space that can be recycled by backends.
         * Allocated data that needs to be available to backends should be
         * allocated in TopMemoryContext.
         */
        PostmasterContext = AllocSetContextCreate(TopMemoryContext,
                                                                                          "Postmaster",
                                                                                          ALLOCSET_DEFAULT_MINSIZE,
                                                                                          ALLOCSET_DEFAULT_INITSIZE,
                                                                                          ALLOCSET_DEFAULT_MAXSIZE);
        MemoryContextSwitchTo(PostmasterContext);

        if (find_my_exec(argv[0], my_exec_path) < 0)
                elog(FATAL, "%s: could not locate my own executable path",
                         argv[0]);

        get_pkglib_path(my_exec_path, pkglib_path);

        /*
         * Options setup
         */
        InitializeGUCOptions();

        opterr = 1;

        /*
         * Parse command-line options.  CAUTION: keep this in sync with
         * tcop/postgres.c (the option sets should not conflict) and with the
         * common help() function in main/main.c.
         */
        while ((opt = getopt(argc, argv, "A:B:c:D:d:EeFf:h:ijk:lN:nOo:Pp:r:S:sTt:W:-:")) != -1)
        {
                switch (opt)
                {
                        case 'A':
                                SetConfigOption("debug_assertions", optarg, PGC_POSTMASTER, PGC_S_ARGV);
                                break;

                        case 'B':
                                SetConfigOption("shared_buffers", optarg, PGC_POSTMASTER, PGC_S_ARGV);
                                break;

                        case 'D':
                                userDoption = optarg;
                                break;

                        case 'd':
                                set_debug_options(atoi(optarg), PGC_POSTMASTER, PGC_S_ARGV);
                                break;

                        case 'E':
                                SetConfigOption("log_statement", "all", PGC_POSTMASTER, PGC_S_ARGV);
                                break;

                        case 'e':
                                SetConfigOption("datestyle", "euro", PGC_POSTMASTER, PGC_S_ARGV);
                                break;

                        case 'F':
                                SetConfigOption("fsync", "false", PGC_POSTMASTER, PGC_S_ARGV);
                                break;

                        case 'f':
                                if (!set_plan_disabling_options(optarg, PGC_POSTMASTER, PGC_S_ARGV))
                                {
                                        write_stderr("%s: invalid argument for option -f: \"%s\"\n",
                                                                 progname, optarg);
                                        ExitPostmaster(1);
                                }
                                break;

                        case 'h':
                                SetConfigOption("listen_addresses", optarg, PGC_POSTMASTER, PGC_S_ARGV);
                                break;

                        case 'i':
                                SetConfigOption("listen_addresses", "*", PGC_POSTMASTER, PGC_S_ARGV);
                                break;

                        case 'j':
                                /* only used by interactive backend */
                                break;

                        case 'k':
                                SetConfigOption("unix_socket_directory", optarg, PGC_POSTMASTER, PGC_S_ARGV);
                                break;

                        case 'l':
                                SetConfigOption("ssl", "true", PGC_POSTMASTER, PGC_S_ARGV);
                                break;

                        case 'N':
                                SetConfigOption("max_connections", optarg, PGC_POSTMASTER, PGC_S_ARGV);
                                break;

                        case 'n':
                                /* Don't reinit shared mem after abnormal exit */
                                Reinit = false;
                                break;

                        case 'O':
                                SetConfigOption("allow_system_table_mods", "true", PGC_POSTMASTER, PGC_S_ARGV);
                                break;

                        case 'o':
                                /* Other options to pass to the backend on the command line */
                                snprintf(ExtraOptions + strlen(ExtraOptions),
                                                 sizeof(ExtraOptions) - strlen(ExtraOptions),
                                                 " %s", optarg);
                                break;

                        case 'P':
                                SetConfigOption("ignore_system_indexes", "true", PGC_POSTMASTER, PGC_S_ARGV);
                                break;

                        case 'p':
                                SetConfigOption("port", optarg, PGC_POSTMASTER, PGC_S_ARGV);
                                break;

                        case 'r':
                                /* only used by single-user backend */
                                break;

                        case 'S':
                                SetConfigOption("work_mem", optarg, PGC_POSTMASTER, PGC_S_ARGV);
                                break;

                        case 's':
                                SetConfigOption("log_statement_stats", "true", PGC_POSTMASTER, PGC_S_ARGV);
                                break;

                        case 'T':

                                /*
                                 * In the event that some backend dumps core, send SIGSTOP,
                                 * rather than SIGQUIT, to all its peers.  This lets the wily
                                 * post_hacker collect core dumps from everyone.
                                 */
                                SendStop = true;
                                break;

                        case 't':
                                {
                                        const char *tmp = get_stats_option_name(optarg);

                                        if (tmp)
                                        {
                                                SetConfigOption(tmp, "true", PGC_POSTMASTER, PGC_S_ARGV);
                                        }
                                        else
                                        {
                                                write_stderr("%s: invalid argument for option -t: \"%s\"\n",
                                                                         progname, optarg);
                                                ExitPostmaster(1);
                                        }
                                        break;
                                }

                        case 'W':
                                SetConfigOption("post_auth_delay", optarg, PGC_POSTMASTER, PGC_S_ARGV);
                                break;

                        case 'c':
                        case '-':
                                {
                                        char       *name,
                                                           *value;

                                        ParseLongOption(optarg, &name, &value);
                                        if (!value)
                                        {
                                                if (opt == '-')
                                                        ereport(ERROR,
                                                                        (errcode(ERRCODE_SYNTAX_ERROR),
                                                                         errmsg("--%s requires a value",
                                                                                        optarg)));
                                                else
                                                        ereport(ERROR,
                                                                        (errcode(ERRCODE_SYNTAX_ERROR),
                                                                         errmsg("-c %s requires a value",
                                                                                        optarg)));
                                        }

                                        SetConfigOption(name, value, PGC_POSTMASTER, PGC_S_ARGV);
                                        free(name);
                                        if (value)
                                                free(value);
                                        break;
                                }

                        default:
                                write_stderr("Try \"%s --help\" for more information.\n",
                                                         progname);
                                ExitPostmaster(1);
                }
        }

        /*
         * Postmaster accepts no non-option switch arguments.
         */
        if (optind < argc)
        {
                write_stderr("%s: invalid argument: \"%s\"\n",
                                         progname, argv[optind]);
                write_stderr("Try \"%s --help\" for more information.\n",
                                         progname);
                ExitPostmaster(1);
        }

#ifdef EXEC_BACKEND
        /* Locate executable backend before we change working directory */
        if (find_other_exec(argv[0], "postgres", PG_BACKEND_VERSIONSTR,
                                                postgres_exec_path) < 0)
                ereport(FATAL,
                                (errmsg("%s: could not locate matching postgres executable",
                                                progname)));
#endif

        /*
         * Locate the proper configuration files and data directory, and read
         * postgresql.conf for the first time.
         */
        if (!SelectConfigFiles(userDoption, progname))
                ExitPostmaster(2);

        /* Verify that DataDir looks reasonable */
        checkDataDir();

        /* And switch working directory into it */
        ChangeToDataDir();

        /*
         * Check for invalid combinations of GUC settings.
         */
        if (ReservedBackends >= MaxBackends)
        {
                write_stderr("%s: superuser_reserved_connections must be less than max_connections\n", progname);
                ExitPostmaster(1);
        }

        /*
         * Other one-time internal sanity checks can go here, if they are fast.
         * (Put any slow processing further down, after postmaster.pid creation.)
         */
        if (!CheckDateTokenTables())
        {
                write_stderr("%s: invalid datetoken tables, please fix\n", progname);
                ExitPostmaster(1);
        }

        /*
         * Now that we are done processing the postmaster arguments, reset
         * getopt(3) library so that it will work correctly in subprocesses.
         */
        optind = 1;
#ifdef HAVE_INT_OPTRESET
        optreset = 1;                           /* some systems need this too */
#endif

        /* For debugging: display postmaster environment */
        {
                extern char **environ;
                char      **p;

                ereport(DEBUG3,
                                (errmsg_internal("%s: PostmasterMain: initial environ dump:",
                                                                 progname)));
                ereport(DEBUG3,
                         (errmsg_internal("-----------------------------------------")));
                for (p = environ; *p; ++p)
                        ereport(DEBUG3,
                                        (errmsg_internal("\t%s", *p)));
                ereport(DEBUG3,
                         (errmsg_internal("-----------------------------------------")));
        }

        /*
         * Fork away from controlling terminal, if -S specified.
         *
         * Must do this before we grab any interlock files, else the interlocks
         * will show the wrong PID.
         */
        if (SilentMode)
                pmdaemonize();

        /*
         * Create lockfile for data directory.
         *
         * We want to do this before we try to grab the input sockets, because the
         * data directory interlock is more reliable than the socket-file
         * interlock (thanks to whoever decided to put socket files in /tmp :-().
         * For the same reason, it's best to grab the TCP socket(s) before the
         * Unix socket.
         */
        CreateDataDirLockFile(true);

        /*
         * If timezone is not set, determine what the OS uses.  (In theory this
         * should be done during GUC initialization, but because it can take as
         * much as several seconds, we delay it until after we've created the
         * postmaster.pid file.  This prevents problems with boot scripts that
         * expect the pidfile to appear quickly.  Also, we avoid problems with
         * trying to locate the timezone files too early in initialization.)
         */
        pg_timezone_initialize();

        /*
         * Likewise, init timezone_abbreviations if not already set.
         */
        pg_timezone_abbrev_initialize();

        /*
         * Initialize SSL library, if specified.
         */
#ifdef USE_SSL
        if (EnableSSL)
                secure_initialize();
#endif

        /*
         * process any libraries that should be preloaded at postmaster start
         */
        process_shared_preload_libraries();

        /*
         * Remove old temporary files.  At this point there can be no other
         * Postgres processes running in this directory, so this should be safe.
         */
        RemovePgTempFiles();

        /*
         * Establish input sockets.
         */
        for (i = 0; i < MAXLISTEN; i++)
                ListenSocket[i] = -1;

        if (ListenAddresses)
        {
                char       *rawstring;
                List       *elemlist;
                ListCell   *l;
                int                     success = 0;

                /* Need a modifiable copy of ListenAddresses */
                rawstring = pstrdup(ListenAddresses);

                /* Parse string into list of identifiers */
                if (!SplitIdentifierString(rawstring, ',', &elemlist))
                {
                        /* syntax error in list */
                        ereport(FATAL,
                                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                         errmsg("invalid list syntax for \"listen_addresses\"")));
                }

                foreach(l, elemlist)
                {
                        char       *curhost = (char *) lfirst(l);

                        if (strcmp(curhost, "*") == 0)
                                status = StreamServerPort(AF_UNSPEC, NULL,
                                                                                  (unsigned short) PostPortNumber,
                                                                                  UnixSocketDir,
                                                                                  ListenSocket, MAXLISTEN);
                        else
                                status = StreamServerPort(AF_UNSPEC, curhost,
                                                                                  (unsigned short) PostPortNumber,
                                                                                  UnixSocketDir,
                                                                                  ListenSocket, MAXLISTEN);
                        if (status == STATUS_OK)
                                success++;
                        else
                                ereport(WARNING,
                                                (errmsg("could not create listen socket for \"%s\"",
                                                                curhost)));
                }

                if (!success && list_length(elemlist))
                        ereport(FATAL,
                                        (errmsg("could not create any TCP/IP sockets")));

                list_free(elemlist);
                pfree(rawstring);
        }

#ifdef USE_BONJOUR
        /* Register for Bonjour only if we opened TCP socket(s) */
        if (ListenSocket[0] != -1 && bonjour_name != NULL)
        {
                DNSServiceRegistrationCreate(bonjour_name,
                                                                         "_postgresql._tcp.",
                                                                         "",
                                                                         htons(PostPortNumber),
                                                                         "",
                                                                         (DNSServiceRegistrationReply) reg_reply,
                                                                         NULL);
        }
#endif

#ifdef HAVE_UNIX_SOCKETS
        status = StreamServerPort(AF_UNIX, NULL,
                                                          (unsigned short) PostPortNumber,
                                                          UnixSocketDir,
                                                          ListenSocket, MAXLISTEN);
        if (status != STATUS_OK)
                ereport(WARNING,
                                (errmsg("could not create Unix-domain socket")));
#endif

        /*
         * check that we have some socket to listen on
         */
        if (ListenSocket[0] == -1)
                ereport(FATAL,
                                (errmsg("no socket created for listening")));

        /*
         * Set up shared memory and semaphores.
         */
        reset_shared(PostPortNumber);

        /*
         * Estimate number of openable files.  This must happen after setting up
         * semaphores, because on some platforms semaphores count as open files.
         */
        set_max_safe_fds();

        /*
         * Load configuration files for client authentication.
         */
        if (!load_hba())
        {
                /* 
                 * It makes no sense continue if we fail to load the HBA file, since 
                 * there is no way to connect to the database in this case.
                 */
                ereport(FATAL,
                                (errmsg("could not load pg_hba.conf")));
        }
        load_ident();

        /*
         * Initialize the list of active backends.
         */
        BackendList = DLNewList();

#ifdef WIN32

        /*
         * Initialize I/O completion port used to deliver list of dead children.
         */
        win32ChildQueue = CreateIoCompletionPort(INVALID_HANDLE_VALUE, NULL, 0, 1);
        if (win32ChildQueue == NULL)
                ereport(FATAL,
                   (errmsg("could not create I/O completion port for child queue")));

        /*
         * Set up a handle that child processes can use to check whether the
         * postmaster is still running.
         */
        if (DuplicateHandle(GetCurrentProcess(),
                                                GetCurrentProcess(),
                                                GetCurrentProcess(),
                                                &PostmasterHandle,
                                                0,
                                                TRUE,
                                                DUPLICATE_SAME_ACCESS) == 0)
                ereport(FATAL,
                                (errmsg_internal("could not duplicate postmaster handle: error code %d",
                                                                 (int) GetLastError())));
#endif

        /*
         * Record postmaster options.  We delay this till now to avoid recording
         * bogus options (eg, NBuffers too high for available memory).
         */
        if (!CreateOptsFile(argc, argv, my_exec_path))
                ExitPostmaster(1);

#ifdef EXEC_BACKEND
        /* Write out nondefault GUC settings for child processes to use */
        write_nondefault_variables(PGC_POSTMASTER);
#endif

        /*
         * Write the external PID file if requested
         */
        if (external_pid_file)
        {
                FILE       *fpidfile = fopen(external_pid_file, "w");

                if (fpidfile)
                {
                        fprintf(fpidfile, "%d\n", MyProcPid);
                        fclose(fpidfile);
                        /* Should we remove the pid file on postmaster exit? */
                }
                else
                        write_stderr("%s: could not write external PID file \"%s\": %s\n",
                                                 progname, external_pid_file, strerror(errno));
        }

        /*
         * Set up signal handlers for the postmaster process.
         *
         * CAUTION: when changing this list, check for side-effects on the signal
         * handling setup of child processes.  See tcop/postgres.c,
         * bootstrap/bootstrap.c, postmaster/bgwriter.c, postmaster/walwriter.c,
         * postmaster/autovacuum.c, postmaster/pgarch.c, postmaster/pgstat.c, and
         * postmaster/syslogger.c.
         */
        pqinitmask();
        PG_SETMASK(&BlockSig);

        pqsignal(SIGHUP, SIGHUP_handler);       /* reread config file and have
                                                                                 * children do same */
        pqsignal(SIGINT, pmdie);        /* send SIGTERM and shut down */
        pqsignal(SIGQUIT, pmdie);       /* send SIGQUIT and die */
        pqsignal(SIGTERM, pmdie);       /* wait for children and shut down */
        pqsignal(SIGALRM, SIG_IGN); /* ignored */
        pqsignal(SIGPIPE, SIG_IGN); /* ignored */
        pqsignal(SIGUSR1, sigusr1_handler); /* message from child process */
        pqsignal(SIGUSR2, dummy_handler);       /* unused, reserve for children */
        pqsignal(SIGCHLD, reaper);      /* handle child termination */
        pqsignal(SIGTTIN, SIG_IGN); /* ignored */
        pqsignal(SIGTTOU, SIG_IGN); /* ignored */
        /* ignore SIGXFSZ, so that ulimit violations work like disk full */
#ifdef SIGXFSZ
        pqsignal(SIGXFSZ, SIG_IGN); /* ignored */
#endif

        /*
         * If enabled, start up syslogger collection subprocess
         */
        SysLoggerPID = SysLogger_Start();

        /*
         * Reset whereToSendOutput from DestDebug (its starting state) to
         * DestNone. This stops ereport from sending log messages to stderr unless
         * Log_destination permits.  We don't do this until the postmaster is
         * fully launched, since startup failures may as well be reported to
         * stderr.
         */
        whereToSendOutput = DestNone;

        /*
         * Initialize stats collection subsystem (this does NOT start the
         * collector process!)
         */
        pgstat_init();

        /*
         * Initialize the autovacuum subsystem (again, no process start yet)
         */
        autovac_init();

        /*
         * Remember postmaster startup time
         */
        PgStartTime = GetCurrentTimestamp();
        /* PostmasterRandom wants its own copy */
        gettimeofday(&random_start_time, NULL);

        /*
         * We're ready to rock and roll...
         */
        StartupPID = StartupDataBase();
        Assert(StartupPID != 0);
        pmState = PM_STARTUP;

        status = ServerLoop();

        /*
         * ServerLoop probably shouldn't ever return, but if it does, close down.
         */
        ExitPostmaster(status != STATUS_OK);

        return 0;                                       /* not reached */
}


/*
 * Validate the proposed data directory
 */
static void
checkDataDir(void)
{
        char            path[MAXPGPATH];
        FILE       *fp;
        struct stat stat_buf;

        Assert(DataDir);

        if (stat(DataDir, &stat_buf) != 0)
        {
                if (errno == ENOENT)
                        ereport(FATAL,
                                        (errcode_for_file_access(),
                                         errmsg("data directory \"%s\" does not exist",
                                                        DataDir)));
                else
                        ereport(FATAL,
                                        (errcode_for_file_access(),
                                 errmsg("could not read permissions of directory \"%s\": %m",
                                                DataDir)));
        }

        /* eventual chdir would fail anyway, but let's test ... */
        if (!S_ISDIR(stat_buf.st_mode))
                ereport(FATAL,
                                (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                                 errmsg("specified data directory \"%s\" is not a directory",
                                                DataDir)));

        /*
         * Check that the directory belongs to my userid; if not, reject.
         *
         * This check is an essential part of the interlock that prevents two
         * postmasters from starting in the same directory (see CreateLockFile()).
         * Do not remove or weaken it.
         *
         * XXX can we safely enable this check on Windows?
         */
#if !defined(WIN32) && !defined(__CYGWIN__)
        if (stat_buf.st_uid != geteuid())
                ereport(FATAL,
                                (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                                 errmsg("data directory \"%s\" has wrong ownership",
                                                DataDir),
                                 errhint("The server must be started by the user that owns the data directory.")));
#endif

        /*
         * Check if the directory has group or world access.  If so, reject.
         *
         * It would be possible to allow weaker constraints (for example, allow
         * group access) but we cannot make a general assumption that that is
         * okay; for example there are platforms where nearly all users
         * customarily belong to the same group.  Perhaps this test should be
         * configurable.
         *
         * XXX temporarily suppress check when on Windows, because there may not
         * be proper support for Unix-y file permissions.  Need to think of a
         * reasonable check to apply on Windows.
         */
#if !defined(WIN32) && !defined(__CYGWIN__)
        if (stat_buf.st_mode & (S_IRWXG | S_IRWXO))
                ereport(FATAL,
                                (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                                 errmsg("data directory \"%s\" has group or world access",
                                                DataDir),
                                 errdetail("Permissions should be u=rwx (0700).")));
#endif

        /* Look for PG_VERSION before looking for pg_control */
        ValidatePgVersion(DataDir);

        snprintf(path, sizeof(path), "%s/global/pg_control", DataDir);

        fp = AllocateFile(path, PG_BINARY_R);
        if (fp == NULL)
        {
                write_stderr("%s: could not find the database system\n"
                                         "Expected to find it in the directory \"%s\",\n"
                                         "but could not open file \"%s\": %s\n",
                                         progname, DataDir, path, strerror(errno));
                ExitPostmaster(2);
        }
        FreeFile(fp);
}


#ifdef USE_BONJOUR

/*
 * empty callback function for DNSServiceRegistrationCreate()
 */
static void
reg_reply(DNSServiceRegistrationReplyErrorType errorCode, void *context)
{
}
#endif   /* USE_BONJOUR */


/*
 * Fork away from the controlling terminal (-S option)
 */
static void
pmdaemonize(void)
{
#ifndef WIN32
        int                     i;
        pid_t           pid;

        pid = fork_process();
        if (pid == (pid_t) -1)
        {
                write_stderr("%s: could not fork background process: %s\n",
                                         progname, strerror(errno));
                ExitPostmaster(1);
        }
        else if (pid)
        {                                                       /* parent */
                /* Parent should just exit, without doing any atexit cleanup */
                _exit(0);
        }

        MyProcPid = PostmasterPid = getpid();           /* reset PID vars to child */

        MyStartTime = time(NULL);

        /*
         * GH: If there's no setsid(), we hopefully don't need silent mode. Until
         * there's a better solution.
         */
#ifdef HAVE_SETSID
        if (setsid() < 0)
        {
                write_stderr("%s: could not dissociate from controlling TTY: %s\n",
                                         progname, strerror(errno));
                ExitPostmaster(1);
        }
#endif
        i = open(DEVNULL, O_RDWR, 0);
        dup2(i, 0);
        dup2(i, 1);
        dup2(i, 2);
        close(i);
#else                                                   /* WIN32 */
        /* not supported */
        elog(FATAL, "SilentMode not supported under WIN32");
#endif   /* WIN32 */
}


/*
 * Main idle loop of postmaster
 */
static int
ServerLoop(void)
{
        fd_set          readmask;
        int                     nSockets;
        time_t          now,
                                last_touch_time;

        last_touch_time = time(NULL);

        nSockets = initMasks(&readmask);

        for (;;)
        {
                fd_set          rmask;
                int                     selres;

                /*
                 * Wait for a connection request to arrive.
                 *
                 * We wait at most one minute, to ensure that the other background
                 * tasks handled below get done even when no requests are arriving.
                 *
                 * If we are in PM_WAIT_DEAD_END state, then we don't want to accept
                 * any new connections, so we don't call select() at all; just sleep
                 * for a little bit with signals unblocked.
                 */
                memcpy((char *) &rmask, (char *) &readmask, sizeof(fd_set));

                PG_SETMASK(&UnBlockSig);

                if (pmState == PM_WAIT_DEAD_END)
                {
                        pg_usleep(100000L); /* 100 msec seems reasonable */
                        selres = 0;
                }
                else
                {
                        /* must set timeout each time; some OSes change it! */
                        struct timeval timeout;

                        timeout.tv_sec = 60;
                        timeout.tv_usec = 0;

                        selres = select(nSockets, &rmask, NULL, NULL, &timeout);
                }

                /*
                 * Block all signals until we wait again.  (This makes it safe for our
                 * signal handlers to do nontrivial work.)
                 */
                PG_SETMASK(&BlockSig);

                /* Now check the select() result */
                if (selres < 0)
                {
                        if (errno != EINTR && errno != EWOULDBLOCK)
                        {
                                ereport(LOG,
                                                (errcode_for_socket_access(),
                                                 errmsg("select() failed in postmaster: %m")));
                                return STATUS_ERROR;
                        }
                }

                /*
                 * New connection pending on any of our sockets? If so, fork a child
                 * process to deal with it.
                 */
                if (selres > 0)
                {
                        int                     i;

                        for (i = 0; i < MAXLISTEN; i++)
                        {
                                if (ListenSocket[i] == -1)
                                        break;
                                if (FD_ISSET(ListenSocket[i], &rmask))
                                {
                                        Port       *port;

                                        port = ConnCreate(ListenSocket[i]);
                                        if (port)
                                        {
                                                BackendStartup(port);

                                                /*
                                                 * We no longer need the open socket or port structure
                                                 * in this process
                                                 */
                                                StreamClose(port->sock);
                                                ConnFree(port);
                                        }
                                }
                        }
                }

                /* If we have lost the log collector, try to start a new one */
                if (SysLoggerPID == 0 && Logging_collector)
                        SysLoggerPID = SysLogger_Start();

                /*
                 * If no background writer process is running, and we are not in a
                 * state that prevents it, start one.  It doesn't matter if this
                 * fails, we'll just try again later.
                 */
                if (BgWriterPID == 0 && pmState == PM_RUN)
                        BgWriterPID = StartBackgroundWriter();

                /*
                 * Likewise, if we have lost the walwriter process, try to start a new
                 * one.
                 */
                if (WalWriterPID == 0 && pmState == PM_RUN)
                        WalWriterPID = StartWalWriter();

                /* If we have lost the autovacuum launcher, try to start a new one */
                if (AutoVacPID == 0 &&
                        (AutoVacuumingActive() || start_autovac_launcher) &&
                        pmState == PM_RUN)
                {
                        AutoVacPID = StartAutoVacLauncher();
                        if (AutoVacPID != 0)
                                start_autovac_launcher = false; /* signal processed */
                }

                /* If we have lost the archiver, try to start a new one */
                if (XLogArchivingActive() && PgArchPID == 0 && pmState == PM_RUN)
                        PgArchPID = pgarch_start();

                /* If we have lost the stats collector, try to start a new one */
                if (PgStatPID == 0 && pmState == PM_RUN)
                        PgStatPID = pgstat_start();

                /*
                 * Touch the socket and lock file every 58 minutes, to ensure that
                 * they are not removed by overzealous /tmp-cleaning tasks.  We assume
                 * no one runs cleaners with cutoff times of less than an hour ...
                 */
                now = time(NULL);
                if (now - last_touch_time >= 58 * SECS_PER_MINUTE)
                {
                        TouchSocketFile();
                        TouchSocketLockFile();
                        last_touch_time = now;
                }
        }
}


/*
 * Initialise the masks for select() for the ports we are listening on.
 * Return the number of sockets to listen on.
 */
static int
initMasks(fd_set *rmask)
{
        int                     maxsock = -1;
        int                     i;

        FD_ZERO(rmask);

        for (i = 0; i < MAXLISTEN; i++)
        {
                int                     fd = ListenSocket[i];

                if (fd == -1)
                        break;
                FD_SET(fd, rmask);
                if (fd > maxsock)
                        maxsock = fd;
        }

        return maxsock + 1;
}


/*
 * Read a client's startup packet and do something according to it.
 *
 * Returns STATUS_OK or STATUS_ERROR, or might call ereport(FATAL) and
 * not return at all.
 *
 * (Note that ereport(FATAL) stuff is sent to the client, so only use it
 * if that's what you want.  Return STATUS_ERROR if you don't want to
 * send anything to the client, which would typically be appropriate
 * if we detect a communications failure.)
 */
static int
ProcessStartupPacket(Port *port, bool SSLdone)
{
        int32           len;
        void       *buf;
        ProtocolVersion proto;
        MemoryContext oldcontext;

        if (pq_getbytes((char *) &len, 4) == EOF)
        {
                /*
                 * EOF after SSLdone probably means the client didn't like our
                 * response to NEGOTIATE_SSL_CODE.      That's not an error condition, so
                 * don't clutter the log with a complaint.
                 */
                if (!SSLdone)
                        ereport(COMMERROR,
                                        (errcode(ERRCODE_PROTOCOL_VIOLATION),
                                         errmsg("incomplete startup packet")));
                return STATUS_ERROR;
        }

        len = ntohl(len);
        len -= 4;

        if (len < (int32) sizeof(ProtocolVersion) ||
                len > MAX_STARTUP_PACKET_LENGTH)
        {
                ereport(COMMERROR,
                                (errcode(ERRCODE_PROTOCOL_VIOLATION),
                                 errmsg("invalid length of startup packet")));
                return STATUS_ERROR;
        }

        /*
         * Allocate at least the size of an old-style startup packet, plus one
         * extra byte, and make sure all are zeroes.  This ensures we will have
         * null termination of all strings, in both fixed- and variable-length
         * packet layouts.
         */
        if (len <= (int32) sizeof(StartupPacket))
                buf = palloc0(sizeof(StartupPacket) + 1);
        else
                buf = palloc0(len + 1);

        if (pq_getbytes(buf, len) == EOF)
        {
                ereport(COMMERROR,
                                (errcode(ERRCODE_PROTOCOL_VIOLATION),
                                 errmsg("incomplete startup packet")));
                return STATUS_ERROR;
        }

        /*
         * The first field is either a protocol version number or a special
         * request code.
         */
        port->proto = proto = ntohl(*((ProtocolVersion *) buf));

        if (proto == CANCEL_REQUEST_CODE)
        {
                processCancelRequest(port, buf);
                return 127;                             /* XXX */
        }

        if (proto == NEGOTIATE_SSL_CODE && !SSLdone)
        {
                char            SSLok;

#ifdef USE_SSL
                /* No SSL when disabled or on Unix sockets */
                if (!EnableSSL || IS_AF_UNIX(port->laddr.addr.ss_family))
                        SSLok = 'N';
                else
                        SSLok = 'S';            /* Support for SSL */
#else
                SSLok = 'N';                    /* No support for SSL */
#endif

retry1:
                if (send(port->sock, &SSLok, 1, 0) != 1)
                {
                        if (errno == EINTR)
                                goto retry1;    /* if interrupted, just retry */
                        ereport(COMMERROR,
                                        (errcode_for_socket_access(),
                                         errmsg("failed to send SSL negotiation response: %m")));
                        return STATUS_ERROR;    /* close the connection */
                }

#ifdef USE_SSL
                if (SSLok == 'S' && secure_open_server(port) == -1)
                        return STATUS_ERROR;
#endif
                /* regular startup packet, cancel, etc packet should follow... */
                /* but not another SSL negotiation request */
                return ProcessStartupPacket(port, true);
        }

        /* Could add additional special packet types here */

        /*
         * Set FrontendProtocol now so that ereport() knows what format to send if
         * we fail during startup.
         */
        FrontendProtocol = proto;

        /* Check we can handle the protocol the frontend is using. */

        if (PG_PROTOCOL_MAJOR(proto) < PG_PROTOCOL_MAJOR(PG_PROTOCOL_EARLIEST) ||
                PG_PROTOCOL_MAJOR(proto) > PG_PROTOCOL_MAJOR(PG_PROTOCOL_LATEST) ||
                (PG_PROTOCOL_MAJOR(proto) == PG_PROTOCOL_MAJOR(PG_PROTOCOL_LATEST) &&
                 PG_PROTOCOL_MINOR(proto) > PG_PROTOCOL_MINOR(PG_PROTOCOL_LATEST)))
                ereport(FATAL,
                                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                                 errmsg("unsupported frontend protocol %u.%u: server supports %u.0 to %u.%u",
                                                PG_PROTOCOL_MAJOR(proto), PG_PROTOCOL_MINOR(proto),
                                                PG_PROTOCOL_MAJOR(PG_PROTOCOL_EARLIEST),
                                                PG_PROTOCOL_MAJOR(PG_PROTOCOL_LATEST),
                                                PG_PROTOCOL_MINOR(PG_PROTOCOL_LATEST))));

        /*
         * Now fetch parameters out of startup packet and save them into the Port
         * structure.  All data structures attached to the Port struct must be
         * allocated in TopMemoryContext so that they won't disappear when we pass
         * them to PostgresMain (see BackendRun).  We need not worry about leaking
         * this storage on failure, since we aren't in the postmaster process
         * anymore.
         */
        oldcontext = MemoryContextSwitchTo(TopMemoryContext);

        if (PG_PROTOCOL_MAJOR(proto) >= 3)
        {
                int32           offset = sizeof(ProtocolVersion);

                /*
                 * Scan packet body for name/option pairs.      We can assume any string
                 * beginning within the packet body is null-terminated, thanks to
                 * zeroing extra byte above.
                 */
                port->guc_options = NIL;

                while (offset < len)
                {
                        char       *nameptr = ((char *) buf) + offset;
                        int32           valoffset;
                        char       *valptr;

                        if (*nameptr == '\0')
                                break;                  /* found packet terminator */
                        valoffset = offset + strlen(nameptr) + 1;
                        if (valoffset >= len)
                                break;                  /* missing value, will complain below */
                        valptr = ((char *) buf) + valoffset;

                        if (strcmp(nameptr, "database") == 0)
                                port->database_name = pstrdup(valptr);
                        else if (strcmp(nameptr, "user") == 0)
                                port->user_name = pstrdup(valptr);
                        else if (strcmp(nameptr, "options") == 0)
                                port->cmdline_options = pstrdup(valptr);
                        else
                        {
                                /* Assume it's a generic GUC option */
                                port->guc_options = lappend(port->guc_options,
                                                                                        pstrdup(nameptr));
                                port->guc_options = lappend(port->guc_options,
                                                                                        pstrdup(valptr));
                        }
                        offset = valoffset + strlen(valptr) + 1;
                }

                /*
                 * If we didn't find a packet terminator exactly at the end of the
                 * given packet length, complain.
                 */
                if (offset != len - 1)
                        ereport(FATAL,
                                        (errcode(ERRCODE_PROTOCOL_VIOLATION),
                                         errmsg("invalid startup packet layout: expected terminator as last byte")));
        }
        else
        {
                /*
                 * Get the parameters from the old-style, fixed-width-fields startup
                 * packet as C strings.  The packet destination was cleared first so a
                 * short packet has zeros silently added.  We have to be prepared to
                 * truncate the pstrdup result for oversize fields, though.
                 */
                StartupPacket *packet = (StartupPacket *) buf;

                port->database_name = pstrdup(packet->database);
                if (strlen(port->database_name) > sizeof(packet->database))
                        port->database_name[sizeof(packet->database)] = '\0';
                port->user_name = pstrdup(packet->user);
                if (strlen(port->user_name) > sizeof(packet->user))
                        port->user_name[sizeof(packet->user)] = '\0';
                port->cmdline_options = pstrdup(packet->options);
                if (strlen(port->cmdline_options) > sizeof(packet->options))
                        port->cmdline_options[sizeof(packet->options)] = '\0';
                port->guc_options = NIL;
        }

        /* Check a user name was given. */
        if (port->user_name == NULL || port->user_name[0] == '\0')
                ereport(FATAL,
                                (errcode(ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION),
                         errmsg("no PostgreSQL user name specified in startup packet")));

        /* The database defaults to the user name. */
        if (port->database_name == NULL || port->database_name[0] == '\0')
                port->database_name = pstrdup(port->user_name);

        if (Db_user_namespace)
        {
                /*
                 * If user@, it is a global user, remove '@'. We only want to do this
                 * if there is an '@' at the end and no earlier in the user string or
                 * they may fake as a local user of another database attaching to this
                 * database.
                 */
                if (strchr(port->user_name, '@') ==
                        port->user_name + strlen(port->user_name) - 1)
                        *strchr(port->user_name, '@') = '\0';
                else
                {
                        /* Append '@' and dbname */
                        char       *db_user;

                        db_user = palloc(strlen(port->user_name) +
                                                         strlen(port->database_name) + 2);
                        sprintf(db_user, "%s@%s", port->user_name, port->database_name);
                        port->user_name = db_user;
                }
        }

        /*
         * Truncate given database and user names to length of a Postgres name.
         * This avoids lookup failures when overlength names are given.
         */
        if (strlen(port->database_name) >= NAMEDATALEN)
                port->database_name[NAMEDATALEN - 1] = '\0';
        if (strlen(port->user_name) >= NAMEDATALEN)
                port->user_name[NAMEDATALEN - 1] = '\0';

        /*
         * Done putting stuff in TopMemoryContext.
         */
        MemoryContextSwitchTo(oldcontext);

        /*
         * If we're going to reject the connection due to database state, say so
         * now instead of wasting cycles on an authentication exchange. (This also
         * allows a pg_ping utility to be written.)
         */
        switch (port->canAcceptConnections)
        {
                case CAC_STARTUP:
                        ereport(FATAL,
                                        (errcode(ERRCODE_CANNOT_CONNECT_NOW),
                                         errmsg("the database system is starting up")));
                        break;
                case CAC_SHUTDOWN:
                        ereport(FATAL,
                                        (errcode(ERRCODE_CANNOT_CONNECT_NOW),
                                         errmsg("the database system is shutting down")));
                        break;
                case CAC_RECOVERY:
                        ereport(FATAL,
                                        (errcode(ERRCODE_CANNOT_CONNECT_NOW),
                                         errmsg("the database system is in recovery mode")));
                        break;
                case CAC_TOOMANY:
                        ereport(FATAL,
                                        (errcode(ERRCODE_TOO_MANY_CONNECTIONS),
                                         errmsg("sorry, too many clients already")));
                        break;
                case CAC_WAITBACKUP:
                        /* OK for now, will check in InitPostgres */
                        break;
                case CAC_OK:
                        break;
        }

        return STATUS_OK;
}


/*
 * The client has sent a cancel request packet, not a normal
 * start-a-new-connection packet.  Perform the necessary processing.
 * Nothing is sent back to the client.
 */
static void
processCancelRequest(Port *port, void *pkt)
{
        CancelRequestPacket *canc = (CancelRequestPacket *) pkt;
        int                     backendPID;
        long            cancelAuthCode;
        Backend    *bp;

#ifndef EXEC_BACKEND
        Dlelem     *curr;
#else
        int                     i;
#endif

        backendPID = (int) ntohl(canc->backendPID);
        cancelAuthCode = (long) ntohl(canc->cancelAuthCode);

        /*
         * See if we have a matching backend.  In the EXEC_BACKEND case, we can no
         * longer access the postmaster's own backend list, and must rely on the
         * duplicate array in shared memory.
         */
#ifndef EXEC_BACKEND
        for (curr = DLGetHead(BackendList); curr; curr = DLGetSucc(curr))
        {
                bp = (Backend *) DLE_VAL(curr);
#else
        for (i = 0; i < NUM_BACKENDARRAY_ELEMS; i++)
        {
                bp = (Backend *) &ShmemBackendArray[i];
#endif
                if (bp->pid == backendPID)
                {
                        if (bp->cancel_key == cancelAuthCode)
                        {
                                /* Found a match; signal that backend to cancel current op */
                                ereport(DEBUG2,
                                                (errmsg_internal("processing cancel request: sending SIGINT to process %d",
                                                                                 backendPID)));
                                signal_child(bp->pid, SIGINT);
                        }
                        else
                                /* Right PID, wrong key: no way, Jose */
                                ereport(LOG,
                                                (errmsg("wrong key in cancel request for process %d",
                                                                backendPID)));
                        return;
                }
        }

        /* No matching backend */
        ereport(LOG,
                        (errmsg("PID %d in cancel request did not match any process",
                                        backendPID)));
}

/*
 * canAcceptConnections --- check to see if database state allows connections.
 */
static enum CAC_state
canAcceptConnections(void)
{
        /*
         * Can't start backends when in startup/shutdown/recovery state.
         *
         * In state PM_WAIT_BACKUP only superusers can connect (this must be
         * allowed so that a superuser can end online backup mode); we return
         * CAC_WAITBACKUP code to indicate that this must be checked later.
         */
        if (pmState != PM_RUN)
        {
                if (pmState == PM_WAIT_BACKUP)
                        return CAC_WAITBACKUP;  /* allow superusers only */
                if (Shutdown > NoShutdown)
                        return CAC_SHUTDOWN;    /* shutdown is pending */
                if (pmState == PM_STARTUP && !FatalError)
                        return CAC_STARTUP; /* normal startup */
                return CAC_RECOVERY;    /* else must be crash recovery */
        }

        /*
         * Don't start too many children.
         *
         * We allow more connections than we can have backends here because some
         * might still be authenticating; they might fail auth, or some existing
         * backend might exit before the auth cycle is completed. The exact
         * MaxBackends limit is enforced when a new backend tries to join the
         * shared-inval backend array.
         *
         * In the EXEC_BACKEND case, the limit here must match the size of the
         * ShmemBackendArray, since all these processes will have cancel codes.
         */
        if (CountChildren() >= 2 * MaxBackends)
                return CAC_TOOMANY;

        return CAC_OK;
}


/*
 * ConnCreate -- create a local connection data structure
 */
static Port *
ConnCreate(int serverFd)
{
        Port       *port;

        if (!(port = (Port *) calloc(1, sizeof(Port))))
        {
                ereport(LOG,
                                (errcode(ERRCODE_OUT_OF_MEMORY),
                                 errmsg("out of memory")));
                ExitPostmaster(1);
        }

        if (StreamConnection(serverFd, port) != STATUS_OK)
        {
                if (port->sock >= 0)
                        StreamClose(port->sock);
                ConnFree(port);
                port = NULL;
        }
        else
        {
                /*
                 * Precompute password salt values to use for this connection. It's
                 * slightly annoying to do this long in advance of knowing whether
                 * we'll need 'em or not, but we must do the random() calls before we
                 * fork, not after.  Else the postmaster's random sequence won't get
                 * advanced, and all backends would end up using the same salt...
                 */
                RandomSalt(port->md5Salt);
        }

        /*
         * Allocate GSSAPI specific state struct
         */
#ifndef EXEC_BACKEND
#if defined(ENABLE_GSS) || defined(ENABLE_SSPI)
        port->gss = (pg_gssinfo *) calloc(1, sizeof(pg_gssinfo));
        if (!port->gss)
        {
                ereport(LOG,
                                (errcode(ERRCODE_OUT_OF_MEMORY),
                                 errmsg("out of memory")));
                ExitPostmaster(1);
        }
#endif
#endif

        return port;
}


/*
 * ConnFree -- free a local connection data structure
 */
static void
ConnFree(Port *conn)
{
#ifdef USE_SSL
        secure_close(conn);
#endif
        if (conn->gss)
                free(conn->gss);
        free(conn);
}


/*
 * ClosePostmasterPorts -- close all the postmaster's open sockets
 *
 * This is called during child process startup to release file descriptors
 * that are not needed by that child process.  The postmaster still has
 * them open, of course.
 *
 * Note: we pass am_syslogger as a boolean because we don't want to set
 * the global variable yet when this is called.
 */
void
ClosePostmasterPorts(bool am_syslogger)
{
        int                     i;

        /* Close the listen sockets */
        for (i = 0; i < MAXLISTEN; i++)
        {
                if (ListenSocket[i] != -1)
                {
                        StreamClose(ListenSocket[i]);
                        ListenSocket[i] = -1;
                }
        }

        /* If using syslogger, close the read side of the pipe */
        if (!am_syslogger)
        {
#ifndef WIN32
                if (syslogPipe[0] >= 0)
                        close(syslogPipe[0]);
                syslogPipe[0] = -1;
#else
                if (syslogPipe[0])
                        CloseHandle(syslogPipe[0]);
                syslogPipe[0] = 0;
#endif
        }
}


/*
 * reset_shared -- reset shared memory and semaphores
 */
static void
reset_shared(int port)
{
        /*
         * Create or re-create shared memory and semaphores.
         *
         * Note: in each "cycle of life" we will normally assign the same IPC keys
         * (if using SysV shmem and/or semas), since the port number is used to
         * determine IPC keys.  This helps ensure that we will clean up dead IPC
         * objects if the postmaster crashes and is restarted.
         */
        CreateSharedMemoryAndSemaphores(false, port);
}


/*
 * SIGHUP -- reread config files, and tell children to do same
 */
static void
SIGHUP_handler(SIGNAL_ARGS)
{
        int                     save_errno = errno;

        PG_SETMASK(&BlockSig);

        if (Shutdown <= SmartShutdown)
        {
                ereport(LOG,
                                (errmsg("received SIGHUP, reloading configuration files")));
                ProcessConfigFile(PGC_SIGHUP);
                SignalChildren(SIGHUP);
                if (BgWriterPID != 0)
                        signal_child(BgWriterPID, SIGHUP);
                if (WalWriterPID != 0)
                        signal_child(WalWriterPID, SIGHUP);
                if (AutoVacPID != 0)
                        signal_child(AutoVacPID, SIGHUP);
                if (PgArchPID != 0)
                        signal_child(PgArchPID, SIGHUP);
                if (SysLoggerPID != 0)
                        signal_child(SysLoggerPID, SIGHUP);
                if (PgStatPID != 0)
                        signal_child(PgStatPID, SIGHUP);

                /* Reload authentication config files too */
                if (!load_hba())
                        ereport(WARNING,
                                        (errmsg("pg_hba.conf not reloaded")));

                load_ident();

#ifdef EXEC_BACKEND
                /* Update the starting-point file for future children */
                write_nondefault_variables(PGC_SIGHUP);
#endif
        }

        PG_SETMASK(&UnBlockSig);

        errno = save_errno;
}


/*
 * pmdie -- signal handler for processing various postmaster signals.
 */
static void
pmdie(SIGNAL_ARGS)
{
        int                     save_errno = errno;

        PG_SETMASK(&BlockSig);

        ereport(DEBUG2,
                        (errmsg_internal("postmaster received signal %d",
                                                         postgres_signal_arg)));

        switch (postgres_signal_arg)
        {
                case SIGTERM:

                        /*
                         * Smart Shutdown:
                         *
                         * Wait for children to end their work, then shut down.
                         */
                        if (Shutdown >= SmartShutdown)
                                break;
                        Shutdown = SmartShutdown;
                        ereport(LOG,
                                        (errmsg("received smart shutdown request")));

                        if (pmState == PM_RUN)
                        {
                                /* autovacuum workers are told to shut down immediately */
                                SignalAutovacWorkers(SIGTERM);
                                /* and the autovac launcher too */
                                if (AutoVacPID != 0)
                                        signal_child(AutoVacPID, SIGTERM);
                                /* and the walwriter too */
                                if (WalWriterPID != 0)
                                        signal_child(WalWriterPID, SIGTERM);
                                pmState = PM_WAIT_BACKUP;
                        }

                        /*
                         * Now wait for online backup mode to end and
                         * backends to exit.  If that is already the case,
                         * PostmasterStateMachine will take the next step.
                         */
                        PostmasterStateMachine();
                        break;

                case SIGINT:

                        /*
                         * Fast Shutdown:
                         *
                         * Abort all children with SIGTERM (rollback active transactions
                         * and exit) and shut down when they are gone.
                         */
                        if (Shutdown >= FastShutdown)
                                break;
                        Shutdown = FastShutdown;
                        ereport(LOG,
                                        (errmsg("received fast shutdown request")));

                        if (StartupPID != 0)
                                signal_child(StartupPID, SIGTERM);
                        if (pmState == PM_RUN || pmState == PM_WAIT_BACKUP)
                        {
                                ereport(LOG,
                                                (errmsg("aborting any active transactions")));
                                /* shut down all backends and autovac workers */
                                SignalChildren(SIGTERM);
                                /* and the autovac launcher too */
                                if (AutoVacPID != 0)
                                        signal_child(AutoVacPID, SIGTERM);
                                /* and the walwriter too */
                                if (WalWriterPID != 0)
                                        signal_child(WalWriterPID, SIGTERM);
                                pmState = PM_WAIT_BACKENDS;
                        }

                        /*
                         * Now wait for backends to exit.  If there are none,
                         * PostmasterStateMachine will take the next step.
                         */
                        PostmasterStateMachine();
                        break;

                case SIGQUIT:

                        /*
                         * Immediate Shutdown:
                         *
                         * abort all children with SIGQUIT and exit without attempt to
                         * properly shut down data base system.
                         */
                        ereport(LOG,
                                        (errmsg("received immediate shutdown request")));
                        SignalChildren(SIGQUIT);
                        if (StartupPID != 0)
                                signal_child(StartupPID, SIGQUIT);
                        if (BgWriterPID != 0)
                                signal_child(BgWriterPID, SIGQUIT);
                        if (WalWriterPID != 0)
                                signal_child(WalWriterPID, SIGQUIT);
                        if (AutoVacPID != 0)
                                signal_child(AutoVacPID, SIGQUIT);
                        if (PgArchPID != 0)
                                signal_child(PgArchPID, SIGQUIT);
                        if (PgStatPID != 0)
                                signal_child(PgStatPID, SIGQUIT);
                        ExitPostmaster(0);
                        break;
        }

        PG_SETMASK(&UnBlockSig);

        errno = save_errno;
}

/*
 * Reaper -- signal handler to cleanup after a child process dies.
 */
static void
reaper(SIGNAL_ARGS)
{
        int                     save_errno = errno;
        int                     pid;                    /* process id of dead child process */
        int                     exitstatus;             /* its exit status */

        /* These macros hide platform variations in getting child status */
#ifdef HAVE_WAITPID
        int                     status;                 /* child exit status */

#define LOOPTEST()              ((pid = waitpid(-1, &status, WNOHANG)) > 0)
#define LOOPHEADER()    (exitstatus = status)
#else                                                   /* !HAVE_WAITPID */
#ifndef WIN32
        union wait      status;                 /* child exit status */

#define LOOPTEST()              ((pid = wait3(&status, WNOHANG, NULL)) > 0)
#define LOOPHEADER()    (exitstatus = status.w_status)
#else                                                   /* WIN32 */
#define LOOPTEST()              ((pid = win32_waitpid(&exitstatus)) > 0)
#define LOOPHEADER()
#endif   /* WIN32 */
#endif   /* HAVE_WAITPID */

        PG_SETMASK(&BlockSig);

        ereport(DEBUG4,
                        (errmsg_internal("reaping dead processes")));

        while (LOOPTEST())
        {
                LOOPHEADER();

                /*
                 * Check if this child was a startup process.
                 */
                if (pid == StartupPID)
                {
                        StartupPID = 0;
                        Assert(pmState == PM_STARTUP);

                        /* FATAL exit of startup is treated as catastrophic */
                        if (!EXIT_STATUS_0(exitstatus))
                        {
                                LogChildExit(LOG, _("startup process"),
                                                         pid, exitstatus);
                                ereport(LOG,
                                (errmsg("aborting startup due to startup process failure")));
                                ExitPostmaster(1);
                        }

                        /*
                         * Startup succeeded - we are done with system startup or
                         * recovery.
                         */
                        FatalError = false;

                        /*
                         * Go to shutdown mode if a shutdown request was pending.
                         */
                        if (Shutdown > NoShutdown)
                        {
                                pmState = PM_WAIT_BACKENDS;
                                /* PostmasterStateMachine logic does the rest */
                                continue;
                        }

                        /*
                         * Otherwise, commence normal operations.
                         */
                        pmState = PM_RUN;

                        /*
                         * Load the flat authorization file into postmaster's cache. The
                         * startup process has recomputed this from the database contents,
                         * so we wait till it finishes before loading it.
                         */
                        load_role();

                        /*
                         * Crank up the background writer.      It doesn't matter if this
                         * fails, we'll just try again later.
                         */
                        Assert(BgWriterPID == 0);
                        BgWriterPID = StartBackgroundWriter();

                        /*
                         * Likewise, start other special children as needed.  In a restart
                         * situation, some of them may be alive already.
                         */
                        if (WalWriterPID == 0)
                                WalWriterPID = StartWalWriter();
                        if (AutoVacuumingActive() && AutoVacPID == 0)
                                AutoVacPID = StartAutoVacLauncher();
                        if (XLogArchivingActive() && PgArchPID == 0)
                                PgArchPID = pgarch_start();
                        if (PgStatPID == 0)
                                PgStatPID = pgstat_start();

                        /* at this point we are really open for business */
                        ereport(LOG,
                                 (errmsg("database system is ready to accept connections")));

                        continue;
                }

                /*
                 * Was it the bgwriter?
                 */
                if (pid == BgWriterPID)
                {
                        BgWriterPID = 0;
                        if (EXIT_STATUS_0(exitstatus) && pmState == PM_SHUTDOWN)
                        {
                                /*
                                 * OK, we saw normal exit of the bgwriter after it's been told
                                 * to shut down.  We expect that it wrote a shutdown
                                 * checkpoint.  (If for some reason it didn't, recovery will
                                 * occur on next postmaster start.)
                                 *
                                 * At this point we should have no normal backend children
                                 * left (else we'd not be in PM_SHUTDOWN state) but we might
                                 * have dead_end children to wait for.
                                 *
                                 * If we have an archiver subprocess, tell it to do a last
                                 * archive cycle and quit; otherwise we can go directly to
                                 * PM_WAIT_DEAD_END state.
                                 */
                                Assert(Shutdown > NoShutdown);

                                if (PgArchPID != 0)
                                {
                                        /* Waken archiver for the last time */
                                        signal_child(PgArchPID, SIGUSR2);
                                        pmState = PM_SHUTDOWN_2;
                                }
                                else
                                        pmState = PM_WAIT_DEAD_END;

                                /*
                                 * We can also shut down the stats collector now; there's
                                 * nothing left for it to do.
                                 */
                                if (PgStatPID != 0)
                                        signal_child(PgStatPID, SIGQUIT);
                        }
                        else
                        {
                                /*
                                 * Any unexpected exit of the bgwriter (including FATAL exit)
                                 * is treated as a crash.
                                 */
                                HandleChildCrash(pid, exitstatus,
                                                                 _("background writer process"));
                        }

                        continue;
                }

                /*
                 * Was it the wal writer?  Normal exit can be ignored; we'll start a
                 * new one at the next iteration of the postmaster's main loop, if
                 * necessary.  Any other exit condition is treated as a crash.
                 */
                if (pid == WalWriterPID)
                {
                        WalWriterPID = 0;
                        if (!EXIT_STATUS_0(exitstatus))
                                HandleChildCrash(pid, exitstatus,
                                                                 _("WAL writer process"));
                        continue;
                }

                /*
                 * Was it the autovacuum launcher?      Normal exit can be ignored; we'll
                 * start a new one at the next iteration of the postmaster's main
                 * loop, if necessary.  Any other exit condition is treated as a
                 * crash.
                 */
                if (pid == AutoVacPID)
                {
                        AutoVacPID = 0;
                        if (!EXIT_STATUS_0(exitstatus))
                                HandleChildCrash(pid, exitstatus,
                                                                 _("autovacuum launcher process"));
                        continue;
                }

                /*
                 * Was it the archiver?  If so, just try to start a new one; no need
                 * to force reset of the rest of the system.  (If fail, we'll try
                 * again in future cycles of the main loop.)  But if we were waiting
                 * for it to shut down, advance to the next shutdown step.
                 */
                if (pid == PgArchPID)
                {
                        PgArchPID = 0;
                        if (!EXIT_STATUS_0(exitstatus))
                                LogChildExit(LOG, _("archiver process"),
                                                         pid, exitstatus);
                        if (XLogArchivingActive() && pmState == PM_RUN)
                                PgArchPID = pgarch_start();
                        else if (pmState == PM_SHUTDOWN_2)
                                pmState = PM_WAIT_DEAD_END;
                        continue;
                }

                /*
                 * Was it the statistics collector?  If so, just try to start a new
                 * one; no need to force reset of the rest of the system.  (If fail,
                 * we'll try again in future cycles of the main loop.)
                 */
                if (pid == PgStatPID)
                {
                        PgStatPID = 0;
                        if (!EXIT_STATUS_0(exitstatus))
                                LogChildExit(LOG, _("statistics collector process"),
                                                         pid, exitstatus);
                        if (pmState == PM_RUN)
                                PgStatPID = pgstat_start();
                        continue;
                }

                /* Was it the system logger?  If so, try to start a new one */
                if (pid == SysLoggerPID)
                {
                        SysLoggerPID = 0;
                        /* for safety's sake, launch new logger *first* */
                        SysLoggerPID = SysLogger_Start();
                        if (!EXIT_STATUS_0(exitstatus))
                                LogChildExit(LOG, _("system logger process"),
                                                         pid, exitstatus);
                        continue;
                }

                /*
                 * Else do standard backend child cleanup.
                 */
                CleanupBackend(pid, exitstatus);
        }                                                       /* loop over pending child-death reports */

        /*
         * After cleaning out the SIGCHLD queue, see if we have any state changes
         * or actions to make.
         */
        PostmasterStateMachine();

        /* Done with signal handler */
        PG_SETMASK(&UnBlockSig);

        errno = save_errno;
}


/*
 * CleanupBackend -- cleanup after terminated backend.
 *
 * Remove all local state associated with backend.
 */
static void
CleanupBackend(int pid,
                           int exitstatus)      /* child's exit status. */
{
        Dlelem     *curr;

        LogChildExit(DEBUG2, _("server process"), pid, exitstatus);

        /*
         * If a backend dies in an ugly way then we must signal all other backends
         * to quickdie.  If exit status is zero (normal) or one (FATAL exit), we
         * assume everything is all right and simply remove the backend from the
         * active backend list.
         */
        if (!EXIT_STATUS_0(exitstatus) && !EXIT_STATUS_1(exitstatus))
        {
                HandleChildCrash(pid, exitstatus, _("server process"));
                return;
        }

        for (curr = DLGetHead(BackendList); curr; curr = DLGetSucc(curr))
        {
                Backend    *bp = (Backend *) DLE_VAL(curr);

                if (bp->pid == pid)
                {
#ifdef EXEC_BACKEND
                        if (!bp->dead_end)
                                ShmemBackendArrayRemove(pid);
#endif
                        DLRemove(curr);
                        free(bp);
                        DLFreeElem(curr);
                        break;
                }
        }
}

/*
 * HandleChildCrash -- cleanup after failed backend, bgwriter, walwriter,
 * or autovacuum.
 *
 * The objectives here are to clean up our local state about the child
 * process, and to signal all other remaining children to quickdie.
 */
static void
HandleChildCrash(int pid, int exitstatus, const char *procname)
{
        Dlelem     *curr,
                           *next;
        Backend    *bp;

        /*
         * Make log entry unless there was a previous crash (if so, nonzero exit
         * status is to be expected in SIGQUIT response; don't clutter log)
         */
        if (!FatalError)
        {
                LogChildExit(LOG, procname, pid, exitstatus);
                ereport(LOG,
                                (errmsg("terminating any other active server processes")));
        }

        /* Process regular backends */
        for (curr = DLGetHead(BackendList); curr; curr = next)
        {
                next = DLGetSucc(curr);
                bp = (Backend *) DLE_VAL(curr);
                if (bp->pid == pid)
                {
                        /*
                         * Found entry for freshly-dead backend, so remove it.
                         */
#ifdef EXEC_BACKEND
                        if (!bp->dead_end)
                                ShmemBackendArrayRemove(pid);
#endif
                        DLRemove(curr);
                        free(bp);
                        DLFreeElem(curr);
                        /* Keep looping so we can signal remaining backends */
                }
                else
                {
                        /*
                         * This backend is still alive.  Unless we did so already, tell it
                         * to commit hara-kiri.
                         *
                         * SIGQUIT is the special signal that says exit without proc_exit
                         * and let the user know what's going on. But if SendStop is set
                         * (-s on command line), then we send SIGSTOP instead, so that we
                         * can get core dumps from all backends by hand.
                         *
                         * We could exclude dead_end children here, but at least in the
                         * SIGSTOP case it seems better to include them.
                         */
                        if (!FatalError)
                        {
                                ereport(DEBUG2,
                                                (errmsg_internal("sending %s to process %d",
                                                                                 (SendStop ? "SIGSTOP" : "SIGQUIT"),
                                                                                 (int) bp->pid)));
                                signal_child(bp->pid, (SendStop ? SIGSTOP : SIGQUIT));
                        }
                }
        }

        /* Take care of the bgwriter too */
        if (pid == BgWriterPID)
                BgWriterPID = 0;
        else if (BgWriterPID != 0 && !FatalError)
        {
                ereport(DEBUG2,
                                (errmsg_internal("sending %s to process %d",
                                                                 (SendStop ? "SIGSTOP" : "SIGQUIT"),
                                                                 (int) BgWriterPID)));
                signal_child(BgWriterPID, (SendStop ? SIGSTOP : SIGQUIT));
        }

        /* Take care of the walwriter too */
        if (pid == WalWriterPID)
                WalWriterPID = 0;
        else if (WalWriterPID != 0 && !FatalError)
        {
                ereport(DEBUG2,
                                (errmsg_internal("sending %s to process %d",
                                                                 (SendStop ? "SIGSTOP" : "SIGQUIT"),
                                                                 (int) WalWriterPID)));
                signal_child(WalWriterPID, (SendStop ? SIGSTOP : SIGQUIT));
        }

        /* Take care of the autovacuum launcher too */
        if (pid == AutoVacPID)
                AutoVacPID = 0;
        else if (AutoVacPID != 0 && !FatalError)
        {
                ereport(DEBUG2,
                                (errmsg_internal("sending %s to process %d",
                                                                 (SendStop ? "SIGSTOP" : "SIGQUIT"),
                                                                 (int) AutoVacPID)));
                signal_child(AutoVacPID, (SendStop ? SIGSTOP : SIGQUIT));
        }

        /*
         * Force a power-cycle of the pgarch process too.  (This isn't absolutely
         * necessary, but it seems like a good idea for robustness, and it
         * simplifies the state-machine logic in the case where a shutdown request
         * arrives during crash processing.)
         */
        if (PgArchPID != 0 && !FatalError)
        {
                ereport(DEBUG2,
                                (errmsg_internal("sending %s to process %d",
                                                                 "SIGQUIT",
                                                                 (int) PgArchPID)));
                signal_child(PgArchPID, SIGQUIT);
        }

        /*
         * Force a power-cycle of the pgstat process too.  (This isn't absolutely
         * necessary, but it seems like a good idea for robustness, and it
         * simplifies the state-machine logic in the case where a shutdown request
         * arrives during crash processing.)
         */
        if (PgStatPID != 0 && !FatalError)
        {
                ereport(DEBUG2,
                                (errmsg_internal("sending %s to process %d",
                                                                 "SIGQUIT",
                                                                 (int) PgStatPID)));
                signal_child(PgStatPID, SIGQUIT);
                allow_immediate_pgstat_restart();
        }

        /* We do NOT restart the syslogger */

        FatalError = true;
        /* We now transit into a state of waiting for children to die */
        if (pmState == PM_RUN ||
                pmState == PM_WAIT_BACKUP ||
                pmState == PM_SHUTDOWN)
                pmState = PM_WAIT_BACKENDS;
}

/*
 * Log the death of a child process.
 */
static void
LogChildExit(int lev, const char *procname, int pid, int exitstatus)
{
        if (WIFEXITED(exitstatus))
                ereport(lev,

                /*------
                  translator: %s is a noun phrase describing a child process, such as
                  "server process" */
                                (errmsg("%s (PID %d) exited with exit code %d",
                                                procname, pid, WEXITSTATUS(exitstatus))));
        else if (WIFSIGNALED(exitstatus))
#if defined(WIN32)
                ereport(lev,

                /*------
                  translator: %s is a noun phrase describing a child process, such as
                  "server process" */
                                (errmsg("%s (PID %d) was terminated by exception 0x%X",
                                                procname, pid, WTERMSIG(exitstatus)),
                                 errhint("See C include file \"ntstatus.h\" for a description of the hexadecimal value.")));
#elif defined(HAVE_DECL_SYS_SIGLIST) && HAVE_DECL_SYS_SIGLIST
        ereport(lev,

        /*------
          translator: %s is a noun phrase describing a child process, such as
          "server process" */
                        (errmsg("%s (PID %d) was terminated by signal %d: %s",
                                        procname, pid, WTERMSIG(exitstatus),
                                        WTERMSIG(exitstatus) < NSIG ?
                                        sys_siglist[WTERMSIG(exitstatus)] : "(unknown)")));
#else
                ereport(lev,

                /*------
                  translator: %s is a noun phrase describing a child process, such as
                  "server process" */
                                (errmsg("%s (PID %d) was terminated by signal %d",
                                                procname, pid, WTERMSIG(exitstatus))));
#endif
        else
                ereport(lev,

                /*------
                  translator: %s is a noun phrase describing a child process, such as
                  "server process" */
                                (errmsg("%s (PID %d) exited with unrecognized status %d",
                                                procname, pid, exitstatus)));
}

/*
 * Advance the postmaster's state machine and take actions as appropriate
 *
 * This is common code for pmdie() and reaper(), which receive the signals
 * that might mean we need to change state.
 */
static void
PostmasterStateMachine(void)
{
        if (pmState == PM_WAIT_BACKUP)
        {
                /*
                 * PM_WAIT_BACKUP state ends when online backup mode is not active.
                 */
                if (!BackupInProgress())
                        pmState = PM_WAIT_BACKENDS;
        }

        /*
         * If we are in a state-machine state that implies waiting for backends to
         * exit, see if they're all gone, and change state if so.
         */
        if (pmState == PM_WAIT_BACKENDS)
        {
                /*
                 * PM_WAIT_BACKENDS state ends when we have no regular backends
                 * (including autovac workers) and no walwriter or autovac launcher.
                 * If we are doing crash recovery then we expect the bgwriter to exit
                 * too, otherwise not.  The archiver, stats, and syslogger processes
                 * are disregarded since they are not connected to shared memory; we
                 * also disregard dead_end children here.
                 */
                if (CountChildren() == 0 &&
                        StartupPID == 0 &&
                        (BgWriterPID == 0 || !FatalError) &&
                        WalWriterPID == 0 &&
                        AutoVacPID == 0)
                {
                        if (FatalError)
                        {
                                /*
                                 * Start waiting for dead_end children to die.  This state
                                 * change causes ServerLoop to stop creating new ones.
                                 */
                                pmState = PM_WAIT_DEAD_END;

                                /*
                                 * We already SIGQUIT'd the archiver and stats processes,
                                 * if any, when we entered FatalError state.
                                 */
                        }
                        else
                        {
                                /*
                                 * If we get here, we are proceeding with normal shutdown. All
                                 * the regular children are gone, and it's time to tell the
                                 * bgwriter to do a shutdown checkpoint.
                                 */
                                Assert(Shutdown > NoShutdown);
                                /* Start the bgwriter if not running */
                                if (BgWriterPID == 0)
                                        BgWriterPID = StartBackgroundWriter();
                                /* And tell it to shut down */
                                if (BgWriterPID != 0)
                                {
                                        signal_child(BgWriterPID, SIGUSR2);
                                        pmState = PM_SHUTDOWN;
                                }
                                else
                                {
                                        /*
                                         * If we failed to fork a bgwriter, just shut down. Any
                                         * required cleanup will happen at next restart. We set
                                         * FatalError so that an "abnormal shutdown" message gets
                                         * logged when we exit.
                                         */
                                        FatalError = true;
                                        pmState = PM_WAIT_DEAD_END;

                                        /* Kill the archiver and stats collector too */
                                        if (PgArchPID != 0)
                                                signal_child(PgArchPID, SIGQUIT);
                                        if (PgStatPID != 0)
                                                signal_child(PgStatPID, SIGQUIT);
                                }
                        }
                }
        }

        if (pmState == PM_WAIT_DEAD_END)
        {
                /*
                 * PM_WAIT_DEAD_END state ends when the BackendList is entirely empty
                 * (ie, no dead_end children remain), and the archiver and stats
                 * collector are gone too.
                 *
                 * The reason we wait for those two is to protect them against a new
                 * postmaster starting conflicting subprocesses; this isn't an
                 * ironclad protection, but it at least helps in the
                 * shutdown-and-immediately-restart scenario.  Note that they have
                 * already been sent appropriate shutdown signals, either during a
                 * normal state transition leading up to PM_WAIT_DEAD_END, or during
                 * FatalError processing.
                 */
                if (DLGetHead(BackendList) == NULL &&
                        PgArchPID == 0 && PgStatPID == 0)
                {
                        /* These other guys should be dead already */
                        Assert(StartupPID == 0);
                        Assert(BgWriterPID == 0);
                        Assert(WalWriterPID == 0);
                        Assert(AutoVacPID == 0);
                        /* syslogger is not considered here */
                        pmState = PM_NO_CHILDREN;
                }
        }

        /*
         * If we've been told to shut down, we exit as soon as there are no
         * remaining children.  If there was a crash, cleanup will occur at the
         * next startup.  (Before PostgreSQL 8.3, we tried to recover from the
         * crash before exiting, but that seems unwise if we are quitting because
         * we got SIGTERM from init --- there may well not be time for recovery
         * before init decides to SIGKILL us.)
         *
         * Note that the syslogger continues to run.  It will exit when it sees
         * EOF on its input pipe, which happens when there are no more upstream
         * processes.
         */
        if (Shutdown > NoShutdown && pmState == PM_NO_CHILDREN)
        {
                if (FatalError)
                {
                        ereport(LOG, (errmsg("abnormal database system shutdown")));
                        ExitPostmaster(1);
                }
                else
                {
                        /*
                         * Terminate backup mode to avoid recovery after a
                         * clean fast shutdown.
                         */
                        CancelBackup();

                        /* Normal exit from the postmaster is here */
                        ExitPostmaster(0);
                }
        }

        /*
         * If we need to recover from a crash, wait for all non-syslogger
         * children to exit, then reset shmem and StartupDataBase.
         */
        if (FatalError && pmState == PM_NO_CHILDREN)
        {
                ereport(LOG,
                                (errmsg("all server processes terminated; reinitializing")));

                shmem_exit(0);
                reset_shared(PostPortNumber);

                StartupPID = StartupDataBase();
                Assert(StartupPID != 0);
                pmState = PM_STARTUP;
        }
}


/*
 * Send a signal to a postmaster child process
 *
 * On systems that have setsid(), each child process sets itself up as a
 * process group leader.  For signals that are generally interpreted in the
 * appropriate fashion, we signal the entire process group not just the
 * direct child process.  This allows us to, for example, SIGQUIT a blocked
 * archive_recovery script, or SIGINT a script being run by a backend via
 * system().
 *
 * There is a race condition for recently-forked children: they might not
 * have executed setsid() yet.  So we signal the child directly as well as
 * the group.  We assume such a child will handle the signal before trying
 * to spawn any grandchild processes.  We also assume that signaling the
 * child twice will not cause any problems.
 */
static void
signal_child(pid_t pid, int signal)
{
        if (kill(pid, signal) < 0)
                elog(DEBUG3, "kill(%ld,%d) failed: %m", (long) pid, signal);
#ifdef HAVE_SETSID
        switch (signal)
        {
                case SIGINT:
                case SIGTERM:
                case SIGQUIT:
                case SIGSTOP:
                        if (kill(-pid, signal) < 0)
                                elog(DEBUG3, "kill(%ld,%d) failed: %m", (long) (-pid), signal);
                        break;
                default:
                        break;
        }
#endif
}

/*
 * Send a signal to all backend children, including autovacuum workers
 * (but NOT special children; dead_end children are never signaled, either).
 * If only_autovac is TRUE, only the autovacuum worker processes are signalled.
 */
static void
SignalSomeChildren(int signal, bool only_autovac)
{
        Dlelem     *curr;

        for (curr = DLGetHead(BackendList); curr; curr = DLGetSucc(curr))
        {
                Backend    *bp = (Backend *) DLE_VAL(curr);

                if (bp->dead_end)
                        continue;
                if (only_autovac && !bp->is_autovacuum)
                        continue;

                ereport(DEBUG4,
                                (errmsg_internal("sending signal %d to process %d",
                                                                 signal, (int) bp->pid)));
                signal_child(bp->pid, signal);
        }
}

/*
 * BackendStartup -- start backend process
 *
 * returns: STATUS_ERROR if the fork failed, STATUS_OK otherwise.
 *
 * Note: if you change this code, also consider StartAutovacuumWorker.
 */
static int
BackendStartup(Port *port)
{
        Backend    *bn;                         /* for backend cleanup */
        pid_t           pid;

        /*
         * Compute the cancel key that will be assigned to this backend. The
         * backend will have its own copy in the forked-off process' value of
         * MyCancelKey, so that it can transmit the key to the frontend.
         */
        MyCancelKey = PostmasterRandom();

        /*
         * Make room for backend data structure.  Better before the fork() so we
         * can handle failure cleanly.
         */
        bn = (Backend *) malloc(sizeof(Backend));
        if (!bn)
        {
                ereport(LOG,
                                (errcode(ERRCODE_OUT_OF_MEMORY),
                                 errmsg("out of memory")));
                return STATUS_ERROR;
        }

        /* Pass down canAcceptConnections state */
        port->canAcceptConnections = canAcceptConnections();

#ifdef EXEC_BACKEND
        pid = backend_forkexec(port);
#else                                                   /* !EXEC_BACKEND */
        pid = fork_process();
        if (pid == 0)                           /* child */
        {
                free(bn);

                /*
                 * Let's clean up ourselves as the postmaster child, and close the
                 * postmaster's listen sockets.  (In EXEC_BACKEND case this is all
                 * done in SubPostmasterMain.)
                 */
                IsUnderPostmaster = true;               /* we are a postmaster subprocess now */

                MyProcPid = getpid();   /* reset MyProcPid */

                MyStartTime = time(NULL);

                /* We don't want the postmaster's proc_exit() handlers */
                on_exit_reset();

                /* Close the postmaster's sockets */
                ClosePostmasterPorts(false);

                /* Perform additional initialization and client authentication */
                BackendInitialize(port);

                /* And run the backend */
                proc_exit(BackendRun(port));
        }
#endif   /* EXEC_BACKEND */

        if (pid < 0)
        {
                /* in parent, fork failed */
                int                     save_errno = errno;

                free(bn);
                errno = save_errno;
                ereport(LOG,
                                (errmsg("could not fork new process for connection: %m")));
                report_fork_failure_to_client(port, save_errno);
                return STATUS_ERROR;
        }

        /* in parent, successful fork */
        ereport(DEBUG2,
                        (errmsg_internal("forked new backend, pid=%d socket=%d",
                                                         (int) pid, port->sock)));

        /*
         * Everything's been successful, it's safe to add this backend to our list
         * of backends.
         */
        bn->pid = pid;
        bn->cancel_key = MyCancelKey;
        bn->is_autovacuum = false;
        bn->dead_end = (port->canAcceptConnections != CAC_OK &&
                                        port->canAcceptConnections != CAC_WAITBACKUP);
        DLAddHead(BackendList, DLNewElem(bn));
#ifdef EXEC_BACKEND
        if (!bn->dead_end)
                ShmemBackendArrayAdd(bn);
#endif

        return STATUS_OK;
}

/*
 * Try to report backend fork() failure to client before we close the
 * connection.  Since we do not care to risk blocking the postmaster on
 * this connection, we set the connection to non-blocking and try only once.
 *
 * This is grungy special-purpose code; we cannot use backend libpq since
 * it's not up and running.
 */
static void
report_fork_failure_to_client(Port *port, int errnum)
{
        char            buffer[1000];
        int                     rc;

        /* Format the error message packet (always V2 protocol) */
        snprintf(buffer, sizeof(buffer), "E%s%s\n",
                         _("could not fork new process for connection: "),
                         strerror(errnum));

        /* Set port to non-blocking.  Don't do send() if this fails */
        if (!pg_set_noblock(port->sock))
                return;

        /* We'll retry after EINTR, but ignore all other failures */
        do
        {
                rc = send(port->sock, buffer, strlen(buffer) + 1, 0);
        } while (rc < 0 && errno == EINTR);
}


/*
 * split_opts -- split a string of options and append it to an argv array
 *
 * NB: the string is destructively modified!
 *
 * Since no current POSTGRES arguments require any quoting characters,
 * we can use the simple-minded tactic of assuming each set of space-
 * delimited characters is a separate argv element.
 *
 * If you don't like that, well, we *used* to pass the whole option string
 * as ONE argument to execl(), which was even less intelligent...
 */
static void
split_opts(char **argv, int *argcp, char *s)
{
        while (s && *s)
        {
                while (isspace((unsigned char) *s))
                        ++s;
                if (*s == '\0')
                        break;
                argv[(*argcp)++] = s;
                while (*s && !isspace((unsigned char) *s))
                        ++s;
                if (*s)
                        *s++ = '\0';
        }
}


/*
 * BackendInitialize -- initialize an interactive (postmaster-child)
 *                              backend process, and perform client authentication.
 *
 * returns: nothing.  Will not return at all if there's any failure.
 *
 * Note: this code does not depend on having any access to shared memory.
 * In the EXEC_BACKEND case, we are physically attached to shared memory
 * but have not yet set up most of our local pointers to shmem structures.
 */
static void
BackendInitialize(Port *port)
{
        int                     status;
        char            remote_host[NI_MAXHOST];
        char            remote_port[NI_MAXSERV];
        char            remote_ps_data[NI_MAXHOST];

        /* Save port etc. for ps status */
        MyProcPort = port;

        /*
         * PreAuthDelay is a debugging aid for investigating problems in the
         * authentication cycle: it can be set in postgresql.conf to allow time to
         * attach to the newly-forked backend with a debugger. (See also the -W
         * backend switch, which we allow clients to pass through PGOPTIONS, but
         * it is not honored until after authentication.)
         */
        if (PreAuthDelay > 0)
                pg_usleep(PreAuthDelay * 1000000L);

        ClientAuthInProgress = true;    /* limit visibility of log messages */

        /* save process start time */
        port->SessionStartTime = GetCurrentTimestamp();
        MyStartTime = timestamptz_to_time_t(port->SessionStartTime);

        /* set these to empty in case they are needed before we set them up */
        port->remote_host = "";
        port->remote_port = "";

        /*
         * Initialize libpq and enable reporting of ereport errors to the client.
         * Must do this now because authentication uses libpq to send messages.
         */
        pq_init();                                      /* initialize libpq to talk to client */
        whereToSendOutput = DestRemote;         /* now safe to ereport to client */

        /*
         * If possible, make this process a group leader, so that the postmaster
         * can signal any child processes too.  (We do this now on the off chance
         * that something might spawn a child process during authentication.)
         */
#ifdef HAVE_SETSID
        if (setsid() < 0)
                elog(FATAL, "setsid() failed: %m");
#endif

        /*
         * We arrange for a simple exit(1) if we receive SIGTERM or SIGQUIT during
         * any client authentication related communication. Otherwise the
         * postmaster cannot shutdown the database FAST or IMMED cleanly if a
         * buggy client blocks a backend during authentication.
         */
        pqsignal(SIGTERM, authdie);
        pqsignal(SIGQUIT, authdie);
        pqsignal(SIGALRM, authdie);
        PG_SETMASK(&AuthBlockSig);

        /*
         * Get the remote host name and port for logging and status display.
         */
        remote_host[0] = '\0';
        remote_port[0] = '\0';
        if (pg_getnameinfo_all(&port->raddr.addr, port->raddr.salen,
                                                   remote_host, sizeof(remote_host),
                                                   remote_port, sizeof(remote_port),
                                           (log_hostname ? 0 : NI_NUMERICHOST) | NI_NUMERICSERV))
        {
                int                     ret = pg_getnameinfo_all(&port->raddr.addr, port->raddr.salen,
                                                                                         remote_host, sizeof(remote_host),
                                                                                         remote_port, sizeof(remote_port),
                                                                                         NI_NUMERICHOST | NI_NUMERICSERV);

                if (ret)
                        ereport(WARNING,
                                        (errmsg_internal("pg_getnameinfo_all() failed: %s",
                                                                         gai_strerror(ret))));
        }
        snprintf(remote_ps_data, sizeof(remote_ps_data),
                         remote_port[0] == '\0' ? "%s" : "%s(%s)",
                         remote_host, remote_port);

        if (Log_connections)
                ereport(LOG,
                                (errmsg("connection received: host=%s%s%s",
                                                remote_host, remote_port[0] ? " port=" : "",
                                                remote_port)));

        /*
         * save remote_host and remote_port in port structure
         */
        port->remote_host = strdup(remote_host);
        port->remote_port = strdup(remote_port);

        /*
         * In EXEC_BACKEND case, we didn't inherit the contents of pg_hba.conf
         * etcetera from the postmaster, and have to load them ourselves. Build
         * the PostmasterContext (which didn't exist before, in this process) to
         * contain the data.
         *
         * FIXME: [fork/exec] Ugh.      Is there a way around this overhead?
         */
#ifdef EXEC_BACKEND
        Assert(PostmasterContext == NULL);
        PostmasterContext = AllocSetContextCreate(TopMemoryContext,
                                                                                          "Postmaster",
                                                                                          ALLOCSET_DEFAULT_MINSIZE,
                                                                                          ALLOCSET_DEFAULT_INITSIZE,
                                                                                          ALLOCSET_DEFAULT_MAXSIZE);
        MemoryContextSwitchTo(PostmasterContext);

        if (!load_hba())
        {
                /* 
                 * It makes no sense continue if we fail to load the HBA file, since 
                 * there is no way to connect to the database in this case.
                 */
                ereport(FATAL,
                                (errmsg("could not load pg_hba.conf")));
        }
        load_ident();
        load_role();
#endif

        /*
         * Ready to begin client interaction.  We will give up and exit(0) after a
         * time delay, so that a broken client can't hog a connection
         * indefinitely.  PreAuthDelay doesn't count against the time limit.
         */
        if (!enable_sig_alarm(AuthenticationTimeout * 1000, false))
                elog(FATAL, "could not set timer for authorization timeout");

        /*
         * Receive the startup packet (which might turn out to be a cancel request
         * packet).
         */
        status = ProcessStartupPacket(port, false);

        if (status != STATUS_OK)
                proc_exit(0);

        /*
         * Now that we have the user and database name, we can set the process
         * title for ps.  It's good to do this as early as possible in startup.
         */
        init_ps_display(port->user_name, port->database_name, remote_ps_data,
                                        update_process_title ? "authentication" : "");

        /*
         * Now perform authentication exchange.
         */
        ClientAuthentication(port); /* might not return, if failure */

        /*
         * Done with authentication.  Disable timeout, and prevent SIGTERM/SIGQUIT
         * again until backend startup is complete.
         */
        if (!disable_sig_alarm(false))
                elog(FATAL, "could not disable timer for authorization timeout");
        PG_SETMASK(&BlockSig);

        if (Log_connections)
                ereport(LOG,
                                (errmsg("connection authorized: user=%s database=%s",
                                                port->user_name, port->database_name)));
}


/*
 * BackendRun -- set up the backend's argument list and invoke PostgresMain()
 *
 * returns:
 *              Shouldn't return at all.
 *              If PostgresMain() fails, return status.
 */
static int
BackendRun(Port *port)
{
        char      **av;
        int                     maxac;
        int                     ac;
        long            secs;
        int                     usecs;
        char            protobuf[32];
        int                     i;

        /*
         * Don't want backend to be able to see the postmaster random number
         * generator state.  We have to clobber the static random_seed *and* start
         * a new random sequence in the random() library function.
         */
        random_seed = 0;
        random_start_time.tv_usec = 0;
        /* slightly hacky way to get integer microseconds part of timestamptz */
        TimestampDifference(0, port->SessionStartTime, &secs, &usecs);
        srandom((unsigned int) (MyProcPid ^ usecs));

        /* ----------------
         * Now, build the argv vector that will be given to PostgresMain.
         *
         * The layout of the command line is
         *              postgres [secure switches] -y databasename [insecure switches]
         * where the switches after -y come from the client request.
         *
         * The maximum possible number of commandline arguments that could come
         * from ExtraOptions or port->cmdline_options is (strlen + 1) / 2; see
         * split_opts().
         * ----------------
         */
        maxac = 10;                                     /* for fixed args supplied below */
        maxac += (strlen(ExtraOptions) + 1) / 2;
        if (port->cmdline_options)
                maxac += (strlen(port->cmdline_options) + 1) / 2;

        av = (char **) MemoryContextAlloc(TopMemoryContext,
                                                                          maxac * sizeof(char *));
        ac = 0;

        av[ac++] = "postgres";

        /*
         * Pass any backend switches specified with -o in the postmaster's own
         * command line.  We assume these are secure.  (It's OK to mangle
         * ExtraOptions now, since we're safely inside a subprocess.)
         */
        split_opts(av, &ac, ExtraOptions);

        /* Tell the backend what protocol the frontend is using. */
        snprintf(protobuf, sizeof(protobuf), "-v%u", port->proto);
        av[ac++] = protobuf;

        /*
         * Tell the backend it is being called from the postmaster, and which
         * database to use.  -y marks the end of secure switches.
         */
        av[ac++] = "-y";
        av[ac++] = port->database_name;

        /*
         * Pass the (insecure) option switches from the connection request. (It's
         * OK to mangle port->cmdline_options now.)
         */
        if (port->cmdline_options)
                split_opts(av, &ac, port->cmdline_options);

        av[ac] = NULL;

        Assert(ac < maxac);

        /*
         * Release postmaster's working memory context so that backend can recycle
         * the space.  Note this does not trash *MyProcPort, because ConnCreate()
         * allocated that space with malloc() ... else we'd need to copy the Port
         * data here.  Also, subsidiary data such as the username isn't lost
         * either; see ProcessStartupPacket().
         */
        MemoryContextSwitchTo(TopMemoryContext);
        MemoryContextDelete(PostmasterContext);
        PostmasterContext = NULL;

        /*
         * Debug: print arguments being passed to backend
         */
        ereport(DEBUG3,
                        (errmsg_internal("%s child[%d]: starting with (",
                                                         progname, (int) getpid())));
        for (i = 0; i < ac; ++i)
                ereport(DEBUG3,
                                (errmsg_internal("\t%s", av[i])));
        ereport(DEBUG3,
                        (errmsg_internal(")")));

        ClientAuthInProgress = false;           /* client_min_messages is active now */

        return (PostgresMain(ac, av, port->user_name));
}


#ifdef EXEC_BACKEND

/*
 * postmaster_forkexec -- fork and exec a postmaster subprocess
 *
 * The caller must have set up the argv array already, except for argv[2]
 * which will be filled with the name of the temp variable file.
 *
 * Returns the child process PID, or -1 on fork failure (a suitable error
 * message has been logged on failure).
 *
 * All uses of this routine will dispatch to SubPostmasterMain in the
 * child process.
 */
pid_t
postmaster_forkexec(int argc, char *argv[])
{
        Port            port;

        /* This entry point passes dummy values for the Port variables */
        memset(&port, 0, sizeof(port));
        return internal_forkexec(argc, argv, &port);
}

/*
 * backend_forkexec -- fork/exec off a backend process
 *
 * Some operating systems (WIN32) don't have fork() so we have to simulate
 * it by storing parameters that need to be passed to the child and
 * then create a new child process.
 *
 * returns the pid of the fork/exec'd process, or -1 on failure
 */
static pid_t
backend_forkexec(Port *port)
{
        char       *av[4];
        int                     ac = 0;

        av[ac++] = "postgres";
        av[ac++] = "--forkbackend";
        av[ac++] = NULL;                        /* filled in by internal_forkexec */

        av[ac] = NULL;
        Assert(ac < lengthof(av));

        return internal_forkexec(ac, av, port);
}

#ifndef WIN32

/*
 * internal_forkexec non-win32 implementation
 *
 * - writes out backend variables to the parameter file
 * - fork():s, and then exec():s the child process
 */
static pid_t
internal_forkexec(int argc, char *argv[], Port *port)
{
        static unsigned long tmpBackendFileNum = 0;
        pid_t           pid;
        char            tmpfilename[MAXPGPATH];
        BackendParameters param;
        FILE       *fp;

        if (!save_backend_variables(&param, port))
                return -1;                              /* log made by save_backend_variables */

        /* Calculate name for temp file */
        snprintf(tmpfilename, MAXPGPATH, "%s/%s.backend_var.%d.%lu",
                         PG_TEMP_FILES_DIR, PG_TEMP_FILE_PREFIX,
                         MyProcPid, ++tmpBackendFileNum);

        /* Open file */
        fp = AllocateFile(tmpfilename, PG_BINARY_W);
        if (!fp)
        {
                /* As in OpenTemporaryFile, try to make the temp-file directory */
                mkdir(PG_TEMP_FILES_DIR, S_IRWXU);

                fp = AllocateFile(tmpfilename, PG_BINARY_W);
                if (!fp)
                {
                        ereport(LOG,
                                        (errcode_for_file_access(),
                                         errmsg("could not create file \"%s\": %m",
                                                        tmpfilename)));
                        return -1;
                }
        }

        if (fwrite(&param, sizeof(param), 1, fp) != 1)
        {
                ereport(LOG,
                                (errcode_for_file_access(),
                                 errmsg("could not write to file \"%s\": %m", tmpfilename)));
                FreeFile(fp);
                return -1;
        }

        /* Release file */
        if (FreeFile(fp))
        {
                ereport(LOG,
                                (errcode_for_file_access(),
                                 errmsg("could not write to file \"%s\": %m", tmpfilename)));
                return -1;
        }

        /* Make sure caller set up argv properly */
        Assert(argc >= 3);
        Assert(argv[argc] == NULL);
        Assert(strncmp(argv[1], "--fork", 6) == 0);
        Assert(argv[2] == NULL);

        /* Insert temp file name after --fork argument */
        argv[2] = tmpfilename;

        /* Fire off execv in child */
        if ((pid = fork_process()) == 0)
        {
                if (execv(postgres_exec_path, argv) < 0)
                {
                        ereport(LOG,
                                        (errmsg("could not execute server process \"%s\": %m",
                                                        postgres_exec_path)));
                        /* We're already in the child process here, can't return */
                        exit(1);
                }
        }

        return pid;                                     /* Parent returns pid, or -1 on fork failure */
}
#else                                                   /* WIN32 */

/*
 * internal_forkexec win32 implementation
 *
 * - starts backend using CreateProcess(), in suspended state
 * - writes out backend variables to the parameter file
 *      - during this, duplicates handles and sockets required for
 *        inheritance into the new process
 * - resumes execution of the new process once the backend parameter
 *       file is complete.
 */
static pid_t
internal_forkexec(int argc, char *argv[], Port *port)
{
        STARTUPINFO si;
        PROCESS_INFORMATION pi;
        int                     i;
        int                     j;
        char            cmdLine[MAXPGPATH * 2];
        HANDLE          paramHandle;
        BackendParameters *param;
        SECURITY_ATTRIBUTES sa;
        char            paramHandleStr[32];
        win32_deadchild_waitinfo *childinfo;

        /* Make sure caller set up argv properly */
        Assert(argc >= 3);
        Assert(argv[argc] == NULL);
        Assert(strncmp(argv[1], "--fork", 6) == 0);
        Assert(argv[2] == NULL);

        /* Set up shared memory for parameter passing */
        ZeroMemory(&sa, sizeof(sa));
        sa.nLength = sizeof(sa);
        sa.bInheritHandle = TRUE;
        paramHandle = CreateFileMapping(INVALID_HANDLE_VALUE,
                                                                        &sa,
                                                                        PAGE_READWRITE,
                                                                        0,
                                                                        sizeof(BackendParameters),
                                                                        NULL);
        if (paramHandle == INVALID_HANDLE_VALUE)
        {
                elog(LOG, "could not create backend parameter file mapping: error code %d",
                         (int) GetLastError());
                return -1;
        }

        param = MapViewOfFile(paramHandle, FILE_MAP_WRITE, 0, 0, sizeof(BackendParameters));
        if (!param)
        {
                elog(LOG, "could not map backend parameter memory: error code %d",
                         (int) GetLastError());
                CloseHandle(paramHandle);
                return -1;
        }

        /* Insert temp file name after --fork argument */
        sprintf(paramHandleStr, "%lu", (DWORD) paramHandle);
        argv[2] = paramHandleStr;

        /* Format the cmd line */
        cmdLine[sizeof(cmdLine) - 1] = '\0';
        cmdLine[sizeof(cmdLine) - 2] = '\0';
        snprintf(cmdLine, sizeof(cmdLine) - 1, "\"%s\"", postgres_exec_path);
        i = 0;
        while (argv[++i] != NULL)
        {
                j = strlen(cmdLine);
                snprintf(cmdLine + j, sizeof(cmdLine) - 1 - j, " \"%s\"", argv[i]);
        }
        if (cmdLine[sizeof(cmdLine) - 2] != '\0')
        {
                elog(LOG, "subprocess command line too long");
                return -1;
        }

        memset(&pi, 0, sizeof(pi));
        memset(&si, 0, sizeof(si));
        si.cb = sizeof(si);

        /*
         * Create the subprocess in a suspended state. This will be resumed later,
         * once we have written out the parameter file.
         */
        if (!CreateProcess(NULL, cmdLine, NULL, NULL, TRUE, CREATE_SUSPENDED,
                                           NULL, NULL, &si, &pi))
        {
                elog(LOG, "CreateProcess call failed: %m (error code %d)",
                         (int) GetLastError());
                return -1;
        }

        if (!save_backend_variables(param, port, pi.hProcess, pi.dwProcessId))
        {
                /*
                 * log made by save_backend_variables, but we have to clean up the
                 * mess with the half-started process
                 */
                if (!TerminateProcess(pi.hProcess, 255))
                        ereport(ERROR,
                                        (errmsg_internal("could not terminate unstarted process: error code %d",
                                                                         (int) GetLastError())));
                CloseHandle(pi.hProcess);
                CloseHandle(pi.hThread);
                return -1;                              /* log made by save_backend_variables */
        }

        /* Drop the shared memory that is now inherited to the backend */
        if (!UnmapViewOfFile(param))
                elog(LOG, "could not unmap view of backend parameter file: error code %d",
                         (int) GetLastError());
        if (!CloseHandle(paramHandle))
                elog(LOG, "could not close handle to backend parameter file: error code %d",
                         (int) GetLastError());

        /*
         * Now that the backend variables are written out, we start the child
         * thread so it can start initializing while we set up the rest of the
         * parent state.
         */
        if (ResumeThread(pi.hThread) == -1)
        {
                if (!TerminateProcess(pi.hProcess, 255))
                {
                        ereport(ERROR,
                                        (errmsg_internal("could not terminate unstartable process: error code %d",
                                                                         (int) GetLastError())));
                        CloseHandle(pi.hProcess);
                        CloseHandle(pi.hThread);
                        return -1;
                }
                CloseHandle(pi.hProcess);
                CloseHandle(pi.hThread);
                ereport(ERROR,
                                (errmsg_internal("could not resume thread of unstarted process: error code %d",
                                                                 (int) GetLastError())));
                return -1;
        }

        /*
         * Queue a waiter for to signal when this child dies. The wait will be
         * handled automatically by an operating system thread pool.
         *
         * Note: use malloc instead of palloc, since it needs to be thread-safe.
         * Struct will be free():d from the callback function that runs on a
         * different thread.
         */
        childinfo = malloc(sizeof(win32_deadchild_waitinfo));
        if (!childinfo)
                ereport(FATAL,
                                (errcode(ERRCODE_OUT_OF_MEMORY),
                                 errmsg("out of memory")));

        childinfo->procHandle = pi.hProcess;
        childinfo->procId = pi.dwProcessId;

        if (!RegisterWaitForSingleObject(&childinfo->waitHandle,
                                                                         pi.hProcess,
                                                                         pgwin32_deadchild_callback,
                                                                         childinfo,
                                                                         INFINITE,
                                                                WT_EXECUTEONLYONCE | WT_EXECUTEINWAITTHREAD))
                ereport(FATAL,
                (errmsg_internal("could not register process for wait: error code %d",
                                                 (int) GetLastError())));

        /* Don't close pi.hProcess here - the wait thread needs access to it */

        CloseHandle(pi.hThread);

        return pi.dwProcessId;
}
#endif   /* WIN32 */


/*
 * SubPostmasterMain -- Get the fork/exec'd process into a state equivalent
 *                      to what it would be if we'd simply forked on Unix, and then
 *                      dispatch to the appropriate place.
 *
 * The first two command line arguments are expected to be "--forkFOO"
 * (where FOO indicates which postmaster child we are to become), and
 * the name of a variables file that we can read to load data that would
 * have been inherited by fork() on Unix.  Remaining arguments go to the
 * subprocess FooMain() routine.
 */
int
SubPostmasterMain(int argc, char *argv[])
{
        Port            port;

        /* Do this sooner rather than later... */
        IsUnderPostmaster = true;       /* we are a postmaster subprocess now */

        MyProcPid = getpid();           /* reset MyProcPid */

        MyStartTime = time(NULL);

        /*
         * make sure stderr is in binary mode before anything can possibly be
         * written to it, in case it's actually the syslogger pipe, so the pipe
         * chunking protocol isn't disturbed. Non-logpipe data gets translated on
         * redirection (e.g. via pg_ctl -l) anyway.
         */
#ifdef WIN32
        _setmode(fileno(stderr), _O_BINARY);
#endif

        /* Lose the postmaster's on-exit routines (really a no-op) */
        on_exit_reset();

        /* In EXEC_BACKEND case we will not have inherited these settings */
        IsPostmasterEnvironment = true;
        whereToSendOutput = DestNone;

        /* Setup essential subsystems (to ensure elog() behaves sanely) */
        MemoryContextInit();
        InitializeGUCOptions();

        /* Read in the variables file */
        memset(&port, 0, sizeof(Port));
        read_backend_variables(argv[2], &port);

        /*
         * Set up memory area for GSS information. Mirrors the code in ConnCreate
         * for the non-exec case.
         */
#if defined(ENABLE_GSS) || defined(ENABLE_SSPI)
        port.gss = (pg_gssinfo *) calloc(1, sizeof(pg_gssinfo));
        if (!port.gss)
                ereport(FATAL,
                                (errcode(ERRCODE_OUT_OF_MEMORY),
                                 errmsg("out of memory")));
#endif


        /* Check we got appropriate args */
        if (argc < 3)
                elog(FATAL, "invalid subpostmaster invocation");

        /*
         * If appropriate, physically re-attach to shared memory segment. We want
         * to do this before going any further to ensure that we can attach at the
         * same address the postmaster used.
         */
        if (strcmp(argv[1], "--forkbackend") == 0 ||
                strcmp(argv[1], "--forkavlauncher") == 0 ||
                strcmp(argv[1], "--forkavworker") == 0 ||
                strcmp(argv[1], "--forkboot") == 0)
                PGSharedMemoryReAttach();

        /* autovacuum needs this set before calling InitProcess */
        if (strcmp(argv[1], "--forkavlauncher") == 0)
                AutovacuumLauncherIAm();
        if (strcmp(argv[1], "--forkavworker") == 0)
                AutovacuumWorkerIAm();

        /*
         * Start our win32 signal implementation. This has to be done after we
         * read the backend variables, because we need to pick up the signal pipe
         * from the parent process.
         */
#ifdef WIN32
        pgwin32_signal_initialize();
#endif

        /* In EXEC_BACKEND case we will not have inherited these settings */
        pqinitmask();
        PG_SETMASK(&BlockSig);

        /* Read in remaining GUC variables */
        read_nondefault_variables();

        /* Run backend or appropriate child */
        if (strcmp(argv[1], "--forkbackend") == 0)
        {
                Assert(argc == 3);              /* shouldn't be any more args */

                /* Close the postmaster's sockets */
                ClosePostmasterPorts(false);

                /*
                 * Need to reinitialize the SSL library in the backend, since the
                 * context structures contain function pointers and cannot be passed
                 * through the parameter file.
                 */
#ifdef USE_SSL
                if (EnableSSL)
                        secure_initialize();
#endif

                /*
                 * process any libraries that should be preloaded at postmaster start
                 *
                 * NOTE: we have to re-load the shared_preload_libraries here because
                 * this backend is not fork()ed so we can't inherit any shared
                 * libraries / DLL's from our parent (the postmaster).
                 */
                process_shared_preload_libraries();

                /*
                 * Perform additional initialization and client authentication.
                 *
                 * We want to do this before InitProcess() for a couple of reasons: 1.
                 * so that we aren't eating up a PGPROC slot while waiting on the
                 * client. 2. so that if InitProcess() fails due to being out of
                 * PGPROC slots, we have already initialized libpq and are able to
                 * report the error to the client.
                 */
                BackendInitialize(&port);

                /* Restore basic shared memory pointers */
                InitShmemAccess(UsedShmemSegAddr);

                /* Need a PGPROC to run CreateSharedMemoryAndSemaphores */
                InitProcess();

                /*
                 * Attach process to shared data structures.  If testing EXEC_BACKEND
                 * on Linux, you must run this as root before starting the postmaster:
                 *
                 * echo 0 >/proc/sys/kernel/randomize_va_space
                 *
                 * This prevents a randomized stack base address that causes child
                 * shared memory to be at a different address than the parent, making
                 * it impossible to attached to shared memory.  Return the value to
                 * '1' when finished.
                 */
                CreateSharedMemoryAndSemaphores(false, 0);

                /* And run the backend */
                proc_exit(BackendRun(&port));
        }
        if (strcmp(argv[1], "--forkboot") == 0)
        {
                /* Close the postmaster's sockets */
                ClosePostmasterPorts(false);

                /* Restore basic shared memory pointers */
                InitShmemAccess(UsedShmemSegAddr);

                /* Need a PGPROC to run CreateSharedMemoryAndSemaphores */
                InitAuxiliaryProcess();

                /* Attach process to shared data structures */
                CreateSharedMemoryAndSemaphores(false, 0);

                AuxiliaryProcessMain(argc - 2, argv + 2);
                proc_exit(0);
        }
        if (strcmp(argv[1], "--forkavlauncher") == 0)
        {
                /* Close the postmaster's sockets */
                ClosePostmasterPorts(false);

                /* Restore basic shared memory pointers */
                InitShmemAccess(UsedShmemSegAddr);

                /* Need a PGPROC to run CreateSharedMemoryAndSemaphores */
                InitAuxiliaryProcess();

                /* Attach process to shared data structures */
                CreateSharedMemoryAndSemaphores(false, 0);

                AutoVacLauncherMain(argc - 2, argv + 2);
                proc_exit(0);
        }
        if (strcmp(argv[1], "--forkavworker") == 0)
        {
                /* Close the postmaster's sockets */
                ClosePostmasterPorts(false);

                /* Restore basic shared memory pointers */
                InitShmemAccess(UsedShmemSegAddr);

                /* Need a PGPROC to run CreateSharedMemoryAndSemaphores */
                InitProcess();

                /* Attach process to shared data structures */
                CreateSharedMemoryAndSemaphores(false, 0);

                AutoVacWorkerMain(argc - 2, argv + 2);
                proc_exit(0);
        }
        if (strcmp(argv[1], "--forkarch") == 0)
        {
                /* Close the postmaster's sockets */
                ClosePostmasterPorts(false);

                /* Do not want to attach to shared memory */

                PgArchiverMain(argc, argv);
                proc_exit(0);
        }
        if (strcmp(argv[1], "--forkcol") == 0)
        {
                /* Close the postmaster's sockets */
                ClosePostmasterPorts(false);

                /* Do not want to attach to shared memory */

                PgstatCollectorMain(argc, argv);
                proc_exit(0);
        }
        if (strcmp(argv[1], "--forklog") == 0)
        {
                /* Close the postmaster's sockets */
                ClosePostmasterPorts(true);

                /* Do not want to attach to shared memory */

                SysLoggerMain(argc, argv);
                proc_exit(0);
        }

        return 1;                                       /* shouldn't get here */
}
#endif   /* EXEC_BACKEND */


/*
 * ExitPostmaster -- cleanup
 *
 * Do NOT call exit() directly --- always go through here!
 */
static void
ExitPostmaster(int status)
{
        /* should cleanup shared memory and kill all backends */

        /*
         * Not sure of the semantics here.      When the Postmaster dies, should the
         * backends all be killed? probably not.
         *
         * MUST         -- vadim 05-10-1999
         */

        proc_exit(status);
}

/*
 * sigusr1_handler - handle signal conditions from child processes
 */
static void
sigusr1_handler(SIGNAL_ARGS)
{
        int                     save_errno = errno;

        PG_SETMASK(&BlockSig);

        if (CheckPostmasterSignal(PMSIGNAL_PASSWORD_CHANGE))
        {
                /*
                 * Authorization file has changed.
                 */
                load_role();
        }

        if (CheckPostmasterSignal(PMSIGNAL_WAKEN_ARCHIVER) &&
                PgArchPID != 0)
        {
                /*
                 * Send SIGUSR1 to archiver process, to wake it up and begin archiving
                 * next transaction log file.
                 */
                signal_child(PgArchPID, SIGUSR1);
        }

        if (CheckPostmasterSignal(PMSIGNAL_ROTATE_LOGFILE) &&
                SysLoggerPID != 0)
        {
                /* Tell syslogger to rotate logfile */
                signal_child(SysLoggerPID, SIGUSR1);
        }

        if (CheckPostmasterSignal(PMSIGNAL_START_AUTOVAC_LAUNCHER))
        {
                /*
                 * Start one iteration of the autovacuum daemon, even if autovacuuming
                 * is nominally not enabled.  This is so we can have an active defense
                 * against transaction ID wraparound.  We set a flag for the main loop
                 * to do it rather than trying to do it here --- this is because the
                 * autovac process itself may send the signal, and we want to handle
                 * that by launching another iteration as soon as the current one
                 * completes.
                 */
                start_autovac_launcher = true;
        }

        if (CheckPostmasterSignal(PMSIGNAL_START_AUTOVAC_WORKER))
        {
                /* The autovacuum launcher wants us to start a worker process. */
                StartAutovacuumWorker();
        }

        PG_SETMASK(&UnBlockSig);

        errno = save_errno;
}


/*
 * Dummy signal handler
 *
 * We use this for signals that we don't actually use in the postmaster,
 * but we do use in backends.  If we were to SIG_IGN such signals in the
 * postmaster, then a newly started backend might drop a signal that arrives
 * before it's able to reconfigure its signal processing.  (See notes in
 * tcop/postgres.c.)
 */
static void
dummy_handler(SIGNAL_ARGS)
{
}

/*
 * RandomSalt
 */
static void
RandomSalt(char *md5Salt)
{
        long            rand;

        /*
         * We use % 255, sacrificing one possible byte value, so as to ensure that
         * all bits of the random() value participate in the result. While at it,
         * add one to avoid generating any null bytes.
         */
        rand = PostmasterRandom();
        md5Salt[0] = (rand % 255) + 1;
        rand = PostmasterRandom();
        md5Salt[1] = (rand % 255) + 1;
        rand = PostmasterRandom();
        md5Salt[2] = (rand % 255) + 1;
        rand = PostmasterRandom();
        md5Salt[3] = (rand % 255) + 1;
}

/*
 * PostmasterRandom
 */
static long
PostmasterRandom(void)
{
        /*
         * Select a random seed at the time of first receiving a request.
         */
        if (random_seed == 0)
        {
                do
                {
                        struct timeval random_stop_time;

                        gettimeofday(&random_stop_time, NULL);

                        /*
                         * We are not sure how much precision is in tv_usec, so we swap
                         * the high and low 16 bits of 'random_stop_time' and XOR them
                         * with 'random_start_time'. On the off chance that the result is
                         * 0, we loop until it isn't.
                         */
                        random_seed = random_start_time.tv_usec ^
                                ((random_stop_time.tv_usec << 16) |
                                 ((random_stop_time.tv_usec >> 16) & 0xffff));
                }
                while (random_seed == 0);

                srandom(random_seed);
        }

        return random();
}

/*
 * Count up number of child processes (excluding special children and
 * dead_end children)
 */
static int
CountChildren(void)
{
        Dlelem     *curr;
        int                     cnt = 0;

        for (curr = DLGetHead(BackendList); curr; curr = DLGetSucc(curr))
        {
                Backend    *bp = (Backend *) DLE_VAL(curr);

                if (!bp->dead_end)
                        cnt++;
        }
        return cnt;
}


/*
 * StartChildProcess -- start an auxiliary process for the postmaster
 *
 * xlop determines what kind of child will be started.  All child types
 * initially go to AuxiliaryProcessMain, which will handle common setup.
 *
 * Return value of StartChildProcess is subprocess' PID, or 0 if failed
 * to start subprocess.
 */
static pid_t
StartChildProcess(AuxProcType type)
{
        pid_t           pid;
        char       *av[10];
        int                     ac = 0;
        char            typebuf[32];

        /*
         * Set up command-line arguments for subprocess
         */
        av[ac++] = "postgres";

#ifdef EXEC_BACKEND
        av[ac++] = "--forkboot";
        av[ac++] = NULL;                        /* filled in by postmaster_forkexec */
#endif

        snprintf(typebuf, sizeof(typebuf), "-x%d", type);
        av[ac++] = typebuf;

        av[ac] = NULL;
        Assert(ac < lengthof(av));

#ifdef EXEC_BACKEND
        pid = postmaster_forkexec(ac, av);
#else                                                   /* !EXEC_BACKEND */
        pid = fork_process();

        if (pid == 0)                           /* child */
        {
                IsUnderPostmaster = true;               /* we are a postmaster subprocess now */

                /* Close the postmaster's sockets */
                ClosePostmasterPorts(false);

                /* Lose the postmaster's on-exit routines and port connections */
                on_exit_reset();

                /* Release postmaster's working memory context */
                MemoryContextSwitchTo(TopMemoryContext);
                MemoryContextDelete(PostmasterContext);
                PostmasterContext = NULL;

                AuxiliaryProcessMain(ac, av);
                ExitPostmaster(0);
        }
#endif   /* EXEC_BACKEND */

        if (pid < 0)
        {
                /* in parent, fork failed */
                int                     save_errno = errno;

                errno = save_errno;
                switch (type)
                {
                        case StartupProcess:
                                ereport(LOG,
                                                (errmsg("could not fork startup process: %m")));
                                break;
                        case BgWriterProcess:
                                ereport(LOG,
                                   (errmsg("could not fork background writer process: %m")));
                                break;
                        case WalWriterProcess:
                                ereport(LOG,
                                                (errmsg("could not fork WAL writer process: %m")));
                                break;
                        default:
                                ereport(LOG,
                                                (errmsg("could not fork process: %m")));
                                break;
                }

                /*
                 * fork failure is fatal during startup, but there's no need to choke
                 * immediately if starting other child types fails.
                 */
                if (type == StartupProcess)
                        ExitPostmaster(1);
                return 0;
        }

        /*
         * in parent, successful fork
         */
        return pid;
}

/*
 * StartAutovacuumWorker
 *              Start an autovac worker process.
 *
 * This function is here because it enters the resulting PID into the
 * postmaster's private backends list.
 *
 * NB -- this code very roughly matches BackendStartup.
 */
static void
StartAutovacuumWorker(void)
{
        Backend    *bn;

        /*
         * If not in condition to run a process, don't try, but handle it like a
         * fork failure.  This does not normally happen, since the signal is only
         * supposed to be sent by autovacuum launcher when it's OK to do it, but
         * we have to check to avoid race-condition problems during DB state
         * changes.
         */
        if (canAcceptConnections() == CAC_OK)
        {
                /*
                 * Compute the cancel key that will be assigned to this session. We
                 * probably don't need cancel keys for autovac workers, but we'd
                 * better have something random in the field to prevent unfriendly
                 * people from sending cancels to them.
                 */
                MyCancelKey = PostmasterRandom();

                bn = (Backend *) malloc(sizeof(Backend));
                if (bn)
                {
                        bn->pid = StartAutoVacWorker();
                        if (bn->pid > 0)
                        {
                                bn->cancel_key = MyCancelKey;
                                bn->is_autovacuum = true;
                                bn->dead_end = false;
                                DLAddHead(BackendList, DLNewElem(bn));
#ifdef EXEC_BACKEND
                                ShmemBackendArrayAdd(bn);
#endif
                                /* all OK */
                                return;
                        }

                        /*
                         * fork failed, fall through to report -- actual error message was
                         * logged by StartAutoVacWorker
                         */
                        free(bn);
                }
                else
                        ereport(LOG,
                                        (errcode(ERRCODE_OUT_OF_MEMORY),
                                         errmsg("out of memory")));
        }

        /*
         * Report the failure to the launcher, if it's running.  (If it's not, we
         * might not even be connected to shared memory, so don't try to call
         * AutoVacWorkerFailed.)
         */
        if (AutoVacPID != 0)
        {
                AutoVacWorkerFailed();
                kill(AutoVacPID, SIGUSR1);
        }
}

/*
 * Create the opts file
 */
static bool
CreateOptsFile(int argc, char *argv[], char *fullprogname)
{
        FILE       *fp;
        int                     i;

#define OPTS_FILE       "postmaster.opts"

        if ((fp = fopen(OPTS_FILE, "w")) == NULL)
        {
                elog(LOG, "could not create file \"%s\": %m", OPTS_FILE);
                return false;
        }

        fprintf(fp, "%s", fullprogname);
        for (i = 1; i < argc; i++)
                fprintf(fp, " \"%s\"", argv[i]);
        fputs("\n", fp);

        if (fclose(fp))
        {
                elog(LOG, "could not write file \"%s\": %m", OPTS_FILE);
                return false;
        }

        return true;
}


#ifdef EXEC_BACKEND

/*
 * The following need to be available to the save/restore_backend_variables
 * functions
 */
extern slock_t *ShmemLock;
extern LWLock *LWLockArray;
extern slock_t *ProcStructLock;
extern PROC_HDR *ProcGlobal;
extern PGPROC *AuxiliaryProcs;
extern int      pgStatSock;

#ifndef WIN32
#define write_inheritable_socket(dest, src, childpid) (*(dest) = (src))
#define read_inheritable_socket(dest, src) (*(dest) = *(src))
#else
static void write_duplicated_handle(HANDLE * dest, HANDLE src, HANDLE child);
static void write_inheritable_socket(InheritableSocket * dest, SOCKET src,
                                                 pid_t childPid);
static void read_inheritable_socket(SOCKET * dest, InheritableSocket * src);
#endif


/* Save critical backend variables into the BackendParameters struct */
#ifndef WIN32
static bool
save_backend_variables(BackendParameters * param, Port *port)
#else
static bool
save_backend_variables(BackendParameters * param, Port *port,
                                           HANDLE childProcess, pid_t childPid)
#endif
{
        memcpy(&param->port, port, sizeof(Port));
        write_inheritable_socket(&param->portsocket, port->sock, childPid);

        strlcpy(param->DataDir, DataDir, MAXPGPATH);

        memcpy(&param->ListenSocket, &ListenSocket, sizeof(ListenSocket));

        param->MyCancelKey = MyCancelKey;

        param->UsedShmemSegID = UsedShmemSegID;
        param->UsedShmemSegAddr = UsedShmemSegAddr;

        param->ShmemLock = ShmemLock;
        param->ShmemVariableCache = ShmemVariableCache;
        param->ShmemBackendArray = ShmemBackendArray;

        param->LWLockArray = LWLockArray;
        param->ProcStructLock = ProcStructLock;
        param->ProcGlobal = ProcGlobal;
        param->AuxiliaryProcs = AuxiliaryProcs;
        write_inheritable_socket(&param->pgStatSock, pgStatSock, childPid);

        param->PostmasterPid = PostmasterPid;
        param->PgStartTime = PgStartTime;
        param->PgReloadTime = PgReloadTime;

        param->redirection_done = redirection_done;

#ifdef WIN32
        param->PostmasterHandle = PostmasterHandle;
        write_duplicated_handle(&param->initial_signal_pipe,
                                                        pgwin32_create_signal_listener(childPid),
                                                        childProcess);
#endif

        memcpy(&param->syslogPipe, &syslogPipe, sizeof(syslogPipe));

        strlcpy(param->my_exec_path, my_exec_path, MAXPGPATH);

        strlcpy(param->pkglib_path, pkglib_path, MAXPGPATH);

        strlcpy(param->ExtraOptions, ExtraOptions, MAXPGPATH);

        strlcpy(param->lc_collate, setlocale(LC_COLLATE, NULL), NAMEDATALEN);
        strlcpy(param->lc_ctype, setlocale(LC_CTYPE, NULL), NAMEDATALEN);

        return true;
}


#ifdef WIN32
/*
 * Duplicate a handle for usage in a child process, and write the child
 * process instance of the handle to the parameter file.
 */
static void
write_duplicated_handle(HANDLE * dest, HANDLE src, HANDLE childProcess)
{
        HANDLE          hChild = INVALID_HANDLE_VALUE;

        if (!DuplicateHandle(GetCurrentProcess(),
                                                 src,
                                                 childProcess,
                                                 &hChild,
                                                 0,
                                                 TRUE,
                                                 DUPLICATE_CLOSE_SOURCE | DUPLICATE_SAME_ACCESS))
                ereport(ERROR,
                                (errmsg_internal("could not duplicate handle to be written to backend parameter file: error code %d",
                                                                 (int) GetLastError())));

        *dest = hChild;
}

/*
 * Duplicate a socket for usage in a child process, and write the resulting
 * structure to the parameter file.
 * This is required because a number of LSPs (Layered Service Providers) very
 * common on Windows (antivirus, firewalls, download managers etc) break
 * straight socket inheritance.
 */
static void
write_inheritable_socket(InheritableSocket * dest, SOCKET src, pid_t childpid)
{
        dest->origsocket = src;
        if (src != 0 && src != -1)
        {
                /* Actual socket */
                if (WSADuplicateSocket(src, childpid, &dest->wsainfo) != 0)
                        ereport(ERROR,
                                        (errmsg("could not duplicate socket %d for use in backend: error code %d",
                                                        src, WSAGetLastError())));
        }
}

/*
 * Read a duplicate socket structure back, and get the socket descriptor.
 */
static void
read_inheritable_socket(SOCKET * dest, InheritableSocket * src)
{
        SOCKET          s;

        if (src->origsocket == -1 || src->origsocket == 0)
        {
                /* Not a real socket! */
                *dest = src->origsocket;
        }
        else
        {
                /* Actual socket, so create from structure */
                s = WSASocket(FROM_PROTOCOL_INFO,
                                          FROM_PROTOCOL_INFO,
                                          FROM_PROTOCOL_INFO,
                                          &src->wsainfo,
                                          0,
                                          0);
                if (s == INVALID_SOCKET)
                {
                        write_stderr("could not create inherited socket: error code %d\n",
                                                 WSAGetLastError());
                        exit(1);
                }
                *dest = s;

                /*
                 * To make sure we don't get two references to the same socket, close
                 * the original one. (This would happen when inheritance actually
                 * works..
                 */
                closesocket(src->origsocket);
        }
}
#endif

static void
read_backend_variables(char *id, Port *port)
{
        BackendParameters param;

#ifndef WIN32
        /* Non-win32 implementation reads from file */
        FILE       *fp;

        /* Open file */
        fp = AllocateFile(id, PG_BINARY_R);
        if (!fp)
        {
                write_stderr("could not read from backend variables file \"%s\": %s\n",
                                         id, strerror(errno));
                exit(1);
        }

        if (fread(&param, sizeof(param), 1, fp) != 1)
        {
                write_stderr("could not read from backend variables file \"%s\": %s\n",
                                         id, strerror(errno));
                exit(1);
        }

        /* Release file */
        FreeFile(fp);
        if (unlink(id) != 0)
        {
                write_stderr("could not remove file \"%s\": %s\n",
                                         id, strerror(errno));
                exit(1);
        }
#else
        /* Win32 version uses mapped file */
        HANDLE          paramHandle;
        BackendParameters *paramp;

        paramHandle = (HANDLE) atol(id);
        paramp = MapViewOfFile(paramHandle, FILE_MAP_READ, 0, 0, 0);
        if (!paramp)
        {
                write_stderr("could not map view of backend variables: error code %d\n",
                                         (int) GetLastError());
                exit(1);
        }

        memcpy(&param, paramp, sizeof(BackendParameters));

        if (!UnmapViewOfFile(paramp))
        {
                write_stderr("could not unmap view of backend variables: error code %d\n",
                                         (int) GetLastError());
                exit(1);
        }

        if (!CloseHandle(paramHandle))
        {
                write_stderr("could not close handle to backend parameter variables: error code %d\n",
                                         (int) GetLastError());
                exit(1);
        }
#endif

        restore_backend_variables(&param, port);
}

/* Restore critical backend variables from the BackendParameters struct */
static void
restore_backend_variables(BackendParameters * param, Port *port)
{
        memcpy(port, &param->port, sizeof(Port));
        read_inheritable_socket(&port->sock, &param->portsocket);

        SetDataDir(param->DataDir);

        memcpy(&ListenSocket, &param->ListenSocket, sizeof(ListenSocket));

        MyCancelKey = param->MyCancelKey;

        UsedShmemSegID = param->UsedShmemSegID;
        UsedShmemSegAddr = param->UsedShmemSegAddr;

        ShmemLock = param->ShmemLock;
        ShmemVariableCache = param->ShmemVariableCache;
        ShmemBackendArray = param->ShmemBackendArray;

        LWLockArray = param->LWLockArray;
        ProcStructLock = param->ProcStructLock;
        ProcGlobal = param->ProcGlobal;
        AuxiliaryProcs = param->AuxiliaryProcs;
        read_inheritable_socket(&pgStatSock, &param->pgStatSock);

        PostmasterPid = param->PostmasterPid;
        PgStartTime = param->PgStartTime;
        PgReloadTime = param->PgReloadTime;

        redirection_done = param->redirection_done;

#ifdef WIN32
        PostmasterHandle = param->PostmasterHandle;
        pgwin32_initial_signal_pipe = param->initial_signal_pipe;
#endif

        memcpy(&syslogPipe, &param->syslogPipe, sizeof(syslogPipe));

        strlcpy(my_exec_path, param->my_exec_path, MAXPGPATH);

        strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);

        strlcpy(ExtraOptions, param->ExtraOptions, MAXPGPATH);

        setlocale(LC_COLLATE, param->lc_collate);
        setlocale(LC_CTYPE, param->lc_ctype);
}


Size
ShmemBackendArraySize(void)
{
        return mul_size(NUM_BACKENDARRAY_ELEMS, sizeof(Backend));
}

void
ShmemBackendArrayAllocation(void)
{
        Size            size = ShmemBackendArraySize();

        ShmemBackendArray = (Backend *) ShmemAlloc(size);
        /* Mark all slots as empty */
        memset(ShmemBackendArray, 0, size);
}

static void
ShmemBackendArrayAdd(Backend *bn)
{
        int                     i;

        /* Find an empty slot */
        for (i = 0; i < NUM_BACKENDARRAY_ELEMS; i++)
        {
                if (ShmemBackendArray[i].pid == 0)
                {
                        ShmemBackendArray[i] = *bn;
                        return;
                }
        }

        ereport(FATAL,
                        (errmsg_internal("no free slots in shmem backend array")));
}

static void
ShmemBackendArrayRemove(pid_t pid)
{
        int                     i;

        for (i = 0; i < NUM_BACKENDARRAY_ELEMS; i++)
        {
                if (ShmemBackendArray[i].pid == pid)
                {
                        /* Mark the slot as empty */
                        ShmemBackendArray[i].pid = 0;
                        return;
                }
        }

        ereport(WARNING,
                        (errmsg_internal("could not find backend entry with pid %d",
                                                         (int) pid)));
}
#endif   /* EXEC_BACKEND */


#ifdef WIN32

static pid_t
win32_waitpid(int *exitstatus)
{
        DWORD           dwd;
        ULONG_PTR       key;
        OVERLAPPED *ovl;

        /*
         * Check if there are any dead children. If there are, return the pid of
         * the first one that died.
         */
        if (GetQueuedCompletionStatus(win32ChildQueue, &dwd, &key, &ovl, 0))
        {
                *exitstatus = (int) key;
                return dwd;
        }

        return -1;
}

/*
 * Note! Code below executes on a thread pool! All operations must
 * be thread safe! Note that elog() and friends must *not* be used.
 */
static void WINAPI
pgwin32_deadchild_callback(PVOID lpParameter, BOOLEAN TimerOrWaitFired)
{
        win32_deadchild_waitinfo *childinfo = (win32_deadchild_waitinfo *) lpParameter;
        DWORD           exitcode;

        if (TimerOrWaitFired)
                return;                                 /* timeout. Should never happen, since we use
                                                                 * INFINITE as timeout value. */

        /*
         * Remove handle from wait - required even though it's set to wait only
         * once
         */
        UnregisterWaitEx(childinfo->waitHandle, NULL);

        if (!GetExitCodeProcess(childinfo->procHandle, &exitcode))
        {
                /*
                 * Should never happen. Inform user and set a fixed exitcode.
                 */
                write_stderr("could not read exit code for process\n");
                exitcode = 255;
        }

        if (!PostQueuedCompletionStatus(win32ChildQueue, childinfo->procId, (ULONG_PTR) exitcode, NULL))
                write_stderr("could not post child completion status\n");

        /*
         * Handle is per-process, so we close it here instead of in the
         * originating thread
         */
        CloseHandle(childinfo->procHandle);

        /*
         * Free struct that was allocated before the call to
         * RegisterWaitForSingleObject()
         */
        free(childinfo);

        /* Queue SIGCHLD signal */
        pg_queue_signal(SIGCHLD);
}

#endif   /* WIN32 */