server/select.c

   1 /*
   2  * Server main select() loop
   3  *
   4  * Copyright (C) 1998 Alexandre Julliard
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * This library is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with this library; if not, write to the Free Software
  18  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  19  */
  20
  21 #include <assert.h>
  22 #include <errno.h>
  23 #include <signal.h>
  24 #include <stdio.h>
  25 #include <stdlib.h>
  26 #include <string.h>
  27 #include <sys/poll.h>
  28 #include <sys/time.h>
  29 #include <sys/types.h>
  30 #include <unistd.h>
  31
  32 #include "object.h"
  33 #include "thread.h"
  34
  35
  36 struct timeout_user
  37 {
  38     struct timeout_user  *next;       /* next in sorted timeout list */
  39     struct timeout_user  *prev;       /* prev in sorted timeout list */
  40     struct timeval        when;       /* timeout expiry (absolute time) */
  41     timeout_callback      callback;   /* callback function */
  42     void                 *private;    /* callback private data */
  43 };
  44
  45 static struct object **poll_users;          /* users array */
  46 static struct pollfd *pollfd;               /* poll fd array */
  47 static int nb_users;                        /* count of array entries actually in use */
  48 static int active_users;                    /* current number of active users */
  49 static int allocated_users;                 /* count of allocated entries in the array */
  50 static struct object **freelist;            /* list of free entries in the array */
  51
  52 static struct timeout_user *timeout_head;   /* sorted timeouts list head */
  53 static struct timeout_user *timeout_tail;   /* sorted timeouts list tail */
  54
  55
  56 /* add a user and return an opaque handle to it, or -1 on failure */
  57 int add_select_user( struct object *obj )
  58 {
  59     int ret;
  60     if (freelist)
  61     {
  62         ret = freelist - poll_users;
  63         freelist = (struct object **)poll_users[ret];
  64     }
  65     else
  66     {
  67         if (nb_users == allocated_users)
  68         {
  69             struct object **newusers;
  70             struct pollfd *newpoll;
  71             int new_count = allocated_users ? (allocated_users + allocated_users / 2) : 16;
  72             if (!(newusers = realloc( poll_users, new_count * sizeof(*poll_users) ))) return -1;
  73             if (!(newpoll = realloc( pollfd, new_count * sizeof(*pollfd) )))
  74             {
  75                 if (allocated_users)
  76                     poll_users = newusers;
  77                 else
  78                     free( newusers );
  79                 obj->select = -1;
  80                 return -1;
  81             }
  82             poll_users = newusers;
  83             pollfd = newpoll;
  84             allocated_users = new_count;
  85         }
  86         ret = nb_users++;
  87     }
  88     pollfd[ret].fd = obj->fd;
  89     pollfd[ret].events = 0;
  90     pollfd[ret].revents = 0;
  91     poll_users[ret] = obj;
  92     obj->select = ret;
  93     active_users++;
  94     return ret;
  95 }
  96
  97 /* remove an object from the select list and close its fd */
  98 void remove_select_user( struct object *obj )
  99 {
 100     int user = obj->select;
 101     assert( user >= 0 );
 102     assert( poll_users[user] == obj );
 103     pollfd[user].fd = -1;
 104     pollfd[user].events = 0;
 105     pollfd[user].revents = 0;
 106     poll_users[user] = (struct object *)freelist;
 107     freelist = &poll_users[user];
 108     close( obj->fd );
 109     obj->fd = -1;
 110     obj->select = -1;
 111     active_users--;
 112 }
 113
 114 /* change the fd and events of an object */
 115 void change_select_fd( struct object *obj, int fd, int events )
 116 {
 117     int user = obj->select;
 118     assert( poll_users[user] == obj );
 119     pollfd[user].fd = fd;
 120     pollfd[user].events = events;
 121     obj->fd = fd;
 122 }
 123
 124 /* set the events that select waits for on this fd */
 125 void set_select_events( struct object *obj, int events )
 126 {
 127     int user = obj->select;
 128     assert( poll_users[user] == obj );
 129     if (events == -1)  /* stop waiting on this fd completely */
 130     {
 131         pollfd[user].fd = -1;
 132         pollfd[user].events = 0;
 133         pollfd[user].revents = 0;
 134     }
 135     else if (pollfd[user].fd != -1) pollfd[user].events = events;
 136 }
 137
 138 /* check if events are pending */
 139 int check_select_events( int fd, int events )
 140 {
 141     struct pollfd pfd;
 142     pfd.fd     = fd;
 143     pfd.events = events;
 144     return poll( &pfd, 1, 0 ) > 0;
 145 }
 146
 147 /* add a timeout user */
 148 struct timeout_user *add_timeout_user( struct timeval *when, timeout_callback func, void *private )
 149 {
 150     struct timeout_user *user;
 151     struct timeout_user *pos;
 152
 153     if (!(user = mem_alloc( sizeof(*user) ))) return NULL;
 154     user->when     = *when;
 155     user->callback = func;
 156     user->private  = private;
 157
 158     /* Now insert it in the linked list */
 159
 160     for (pos = timeout_head; pos; pos = pos->next)
 161         if (!time_before( &pos->when, when )) break;
 162
 163     if (pos)  /* insert it before 'pos' */
 164     {
 165         if ((user->prev = pos->prev)) user->prev->next = user;
 166         else timeout_head = user;
 167         user->next = pos;
 168         pos->prev = user;
 169     }
 170     else  /* insert it at the tail */
 171     {
 172         user->next = NULL;
 173         if (timeout_tail) timeout_tail->next = user;
 174         else timeout_head = user;
 175         user->prev = timeout_tail;
 176         timeout_tail = user;
 177     }
 178     return user;
 179 }
 180
 181 /* remove a timeout user */
 182 void remove_timeout_user( struct timeout_user *user )
 183 {
 184     if (user->next) user->next->prev = user->prev;
 185     else timeout_tail = user->prev;
 186     if (user->prev) user->prev->next = user->next;
 187     else timeout_head = user->next;
 188     free( user );
 189 }
 190
 191 /* add a timeout in milliseconds to an absolute time */
 192 void add_timeout( struct timeval *when, int timeout )
 193 {
 194     if (timeout)
 195     {
 196         long sec = timeout / 1000;
 197         if ((when->tv_usec += (timeout - 1000*sec) * 1000) >= 1000000)
 198         {
 199             when->tv_usec -= 1000000;
 200             when->tv_sec++;
 201         }
 202         when->tv_sec += sec;
 203     }
 204 }
 205
 206 /* handle the next expired timeout */
 207 static void handle_timeout(void)
 208 {
 209     struct timeout_user *user = timeout_head;
 210     timeout_head = user->next;
 211     if (user->next) user->next->prev = user->prev;
 212     else timeout_tail = user->prev;
 213     user->callback( user->private );
 214     free( user );
 215 }
 216
 217 /* SIGHUP handler */
 218 static void sighup_handler()
 219 {
 220 #ifdef DEBUG_OBJECTS
 221     dump_objects();
 222 #endif
 223 }
 224
 225 /* SIGTERM handler */
 226 static void sigterm_handler()
 227 {
 228     close_registry();
 229     exit(1);
 230 }
 231
 232 /* server main loop */
 233 void select_loop(void)
 234 {
 235     int ret;
 236     sigset_t sigset;
 237     struct sigaction action;
 238
 239     /* block the signals we use */
 240     sigemptyset( &sigset );
 241     sigaddset( &sigset, SIGCHLD );
 242     sigaddset( &sigset, SIGHUP );
 243     sigaddset( &sigset, SIGINT );
 244     sigaddset( &sigset, SIGQUIT );
 245     sigaddset( &sigset, SIGTERM );
 246     sigprocmask( SIG_BLOCK, &sigset, NULL );
 247
 248     /* set the handlers */
 249     action.sa_mask = sigset;
 250     action.sa_flags = 0;
 251     action.sa_handler = sigchld_handler;
 252     sigaction( SIGCHLD, &action, NULL );
 253     action.sa_handler = sighup_handler;
 254     sigaction( SIGHUP, &action, NULL );
 255     action.sa_handler = sigterm_handler;
 256     sigaction( SIGINT, &action, NULL );
 257     sigaction( SIGQUIT, &action, NULL );
 258     sigaction( SIGTERM, &action, NULL );
 259
 260     while (active_users)
 261     {
 262         long diff = -1;
 263         if (timeout_head)
 264         {
 265             struct timeval now;
 266             gettimeofday( &now, NULL );
 267             while (timeout_head)
 268             {
 269                 if (!time_before( &now, &timeout_head->when )) handle_timeout();
 270                 else
 271                 {
 272                     diff = (timeout_head->when.tv_sec - now.tv_sec) * 1000
 273                             + (timeout_head->when.tv_usec - now.tv_usec) / 1000;
 274                     break;
 275                 }
 276             }
 277             if (!active_users) break;  /* last user removed by a timeout */
 278         }
 279
 280         sigprocmask( SIG_UNBLOCK, &sigset, NULL );
 281
 282         /* Note: we assume that the signal handlers do not manipulate the pollfd array
 283          *       or the timeout list, otherwise there is a race here.
 284          */
 285         ret = poll( pollfd, nb_users, diff );
 286
 287         sigprocmask( SIG_BLOCK, &sigset, NULL );
 288
 289         if (ret > 0)
 290         {
 291             int i;
 292             for (i = 0; i < nb_users; i++)
 293             {
 294                 if (pollfd[i].revents)
 295                 {
 296                     poll_users[i]->ops->poll_event( poll_users[i], pollfd[i].revents );
 297                     if (!--ret) break;
 298                 }
 299             }
 300         }
 301     }
 302 }