server/select.c

   1 /*
   2  * Server main select() loop
   3  *
   4  * Copyright (C) 1998 Alexandre Julliard
   5  */
   6
   7 #include <assert.h>
   8 #include <errno.h>
   9 #include <signal.h>
  10 #include <stdio.h>
  11 #include <stdlib.h>
  12 #include <string.h>
  13 #include <sys/poll.h>
  14 #include <sys/time.h>
  15 #include <sys/types.h>
  16 #include <unistd.h>
  17
  18 #include "object.h"
  19 #include "thread.h"
  20
  21
  22 struct timeout_user
  23 {
  24     struct timeout_user  *next;       /* next in sorted timeout list */
  25     struct timeout_user  *prev;       /* prev in sorted timeout list */
  26     struct timeval        when;       /* timeout expiry (absolute time) */
  27     timeout_callback      callback;   /* callback function */
  28     void                 *private;    /* callback private data */
  29 };
  30
  31 static struct object **poll_users;          /* users array */
  32 static struct pollfd *pollfd;               /* poll fd array */
  33 static int nb_users;                        /* count of array entries actually in use */
  34 static int active_users;                    /* current number of active users */
  35 static int allocated_users;                 /* count of allocated entries in the array */
  36 static struct object **freelist;            /* list of free entries in the array */
  37
  38 static struct timeout_user *timeout_head;   /* sorted timeouts list head */
  39 static struct timeout_user *timeout_tail;   /* sorted timeouts list tail */
  40
  41
  42 /* add a user and return an opaque handle to it, or -1 on failure */
  43 int add_select_user( struct object *obj )
  44 {
  45     int ret;
  46     if (freelist)
  47     {
  48         ret = freelist - poll_users;
  49         freelist = (struct object **)poll_users[ret];
  50     }
  51     else
  52     {
  53         if (nb_users == allocated_users)
  54         {
  55             struct object **newusers;
  56             struct pollfd *newpoll;
  57             int new_count = allocated_users ? (allocated_users + allocated_users / 2) : 16;
  58             if (!(newusers = realloc( poll_users, new_count * sizeof(*poll_users) ))) return -1;
  59             if (!(newpoll = realloc( pollfd, new_count * sizeof(*pollfd) )))
  60             {
  61                 free( newusers );
  62                 return -1;
  63             }
  64             poll_users = newusers;
  65             pollfd = newpoll;
  66             allocated_users = new_count;
  67         }
  68         ret = nb_users++;
  69     }
  70     pollfd[ret].fd = obj->fd;
  71     pollfd[ret].events = 0;
  72     pollfd[ret].revents = 0;
  73     poll_users[ret] = obj;
  74     obj->select = ret;
  75     active_users++;
  76     return ret;
  77 }
  78
  79 /* remove an object from the select list and close its fd */
  80 void remove_select_user( struct object *obj )
  81 {
  82     int user = obj->select;
  83     assert( poll_users[user] == obj );
  84     pollfd[user].fd = -1;
  85     pollfd[user].events = 0;
  86     pollfd[user].revents = 0;
  87     poll_users[user] = (struct object *)freelist;
  88     freelist = &poll_users[user];
  89     close( obj->fd );
  90     obj->fd = -1;
  91     obj->select = -1;
  92     active_users--;
  93 }
  94
  95 /* change the fd of an object (the old fd is closed) */
  96 void change_select_fd( struct object *obj, int fd )
  97 {
  98     int user = obj->select;
  99     assert( poll_users[user] == obj );
 100     pollfd[user].fd = fd;
 101     close( obj->fd );
 102     obj->fd = fd;
 103 }
 104
 105 /* set the events that select waits for on this fd */
 106 void set_select_events( struct object *obj, int events )
 107 {
 108     int user = obj->select;
 109     assert( poll_users[user] == obj );
 110     if (events == -1)  /* stop waiting on this fd completely */
 111     {
 112         pollfd[user].fd = -1;
 113         pollfd[user].events = 0;
 114         pollfd[user].revents = 0;
 115     }
 116     else if (pollfd[user].fd != -1) pollfd[user].events = events;
 117 }
 118
 119 /* check if events are pending */
 120 int check_select_events( int fd, int events )
 121 {
 122     struct pollfd pfd;
 123     pfd.fd     = fd;
 124     pfd.events = events;
 125     return poll( &pfd, 1, 0 ) > 0;
 126 }
 127
 128 /* add a timeout user */
 129 struct timeout_user *add_timeout_user( struct timeval *when, timeout_callback func, void *private )
 130 {
 131     struct timeout_user *user;
 132     struct timeout_user *pos;
 133
 134     if (!(user = mem_alloc( sizeof(*user) ))) return NULL;
 135     user->when     = *when;
 136     user->callback = func;
 137     user->private  = private;
 138
 139     /* Now insert it in the linked list */
 140
 141     for (pos = timeout_head; pos; pos = pos->next)
 142         if (!time_before( &pos->when, when )) break;
 143
 144     if (pos)  /* insert it before 'pos' */
 145     {
 146         if ((user->prev = pos->prev)) user->prev->next = user;
 147         else timeout_head = user;
 148         user->next = pos;
 149         pos->prev = user;
 150     }
 151     else  /* insert it at the tail */
 152     {
 153         user->next = NULL;
 154         if (timeout_tail) timeout_tail->next = user;
 155         else timeout_head = user;
 156         user->prev = timeout_tail;
 157         timeout_tail = user;
 158     }
 159     return user;
 160 }
 161
 162 /* remove a timeout user */
 163 void remove_timeout_user( struct timeout_user *user )
 164 {
 165     if (user->next) user->next->prev = user->prev;
 166     else timeout_tail = user->prev;
 167     if (user->prev) user->prev->next = user->next;
 168     else timeout_head = user->next;
 169     free( user );
 170 }
 171
 172 /* add a timeout in milliseconds to an absolute time */
 173 void add_timeout( struct timeval *when, int timeout )
 174 {
 175     if (timeout)
 176     {
 177         long sec = timeout / 1000;
 178         if ((when->tv_usec += (timeout - 1000*sec) * 1000) >= 1000000)
 179         {
 180             when->tv_usec -= 1000000;
 181             when->tv_sec++;
 182         }
 183         when->tv_sec += sec;
 184     }
 185 }
 186
 187 /* handle the next expired timeout */
 188 static void handle_timeout(void)
 189 {
 190     struct timeout_user *user = timeout_head;
 191     timeout_head = user->next;
 192     if (user->next) user->next->prev = user->prev;
 193     else timeout_tail = user->prev;
 194     user->callback( user->private );
 195     free( user );
 196 }
 197
 198 /* SIGHUP handler */
 199 static void sighup_handler()
 200 {
 201 #ifdef DEBUG_OBJECTS
 202     dump_objects();
 203 #endif
 204 }
 205
 206 /* server main loop */
 207 void select_loop(void)
 208 {
 209     int ret;
 210     sigset_t sigset;
 211     struct sigaction action;
 212
 213     /* block the signals we use */
 214     sigemptyset( &sigset );
 215     sigaddset( &sigset, SIGCHLD );
 216     sigaddset( &sigset, SIGHUP );
 217     sigprocmask( SIG_BLOCK, &sigset, NULL );
 218
 219     /* set the handlers */
 220     action.sa_mask = sigset;
 221     action.sa_flags = 0;
 222     action.sa_handler = sigchld_handler;
 223     sigaction( SIGCHLD, &action, NULL );
 224     action.sa_handler = sighup_handler;
 225     sigaction( SIGHUP, &action, NULL );
 226
 227     while (active_users)
 228     {
 229         long diff = -1;
 230         if (timeout_head)
 231         {
 232             struct timeval now;
 233             gettimeofday( &now, NULL );
 234             while (timeout_head)
 235             {
 236                 if (!time_before( &now, &timeout_head->when )) handle_timeout();
 237                 else
 238                 {
 239                     diff = (timeout_head->when.tv_sec - now.tv_sec) * 1000
 240                             + (timeout_head->when.tv_usec - now.tv_usec) / 1000;
 241                     break;
 242                 }
 243             }
 244         }
 245
 246         sigprocmask( SIG_UNBLOCK, &sigset, NULL );
 247
 248         /* Note: we assume that the signal handlers do not manipulate the pollfd array
 249          *       or the timeout list, otherwise there is a race here.
 250          */
 251         ret = poll( pollfd, nb_users, diff );
 252
 253         sigprocmask( SIG_BLOCK, &sigset, NULL );
 254
 255         if (ret > 0)
 256         {
 257             int i;
 258             for (i = 0; i < nb_users; i++)
 259             {
 260                 if (pollfd[i].revents)
 261                 {
 262                     poll_users[i]->ops->poll_event( poll_users[i], pollfd[i].revents );
 263                     if (!--ret) break;
 264                 }
 265             }
 266         }
 267     }
 268 }