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                 if (allocated_users)
  62                     poll_users = newusers;
  63                 else
  64                     free( newusers );
  65                 obj->select = -1;
  66                 return -1;
  67             }
  68             poll_users = newusers;
  69             pollfd = newpoll;
  70             allocated_users = new_count;
  71         }
  72         ret = nb_users++;
  73     }
  74     pollfd[ret].fd = obj->fd;
  75     pollfd[ret].events = 0;
  76     pollfd[ret].revents = 0;
  77     poll_users[ret] = obj;
  78     obj->select = ret;
  79     active_users++;
  80     return ret;
  81 }
  82
  83 /* remove an object from the select list and close its fd */
  84 void remove_select_user( struct object *obj )
  85 {
  86     int user = obj->select;
  87     assert( user >= 0 );
  88     assert( poll_users[user] == obj );
  89     pollfd[user].fd = -1;
  90     pollfd[user].events = 0;
  91     pollfd[user].revents = 0;
  92     poll_users[user] = (struct object *)freelist;
  93     freelist = &poll_users[user];
  94     close( obj->fd );
  95     obj->fd = -1;
  96     obj->select = -1;
  97     active_users--;
  98 }
  99
 100 /* change the fd and events of an object */
 101 void change_select_fd( struct object *obj, int fd, int events )
 102 {
 103     int user = obj->select;
 104     assert( poll_users[user] == obj );
 105     pollfd[user].fd = fd;
 106     pollfd[user].events = events;
 107     obj->fd = fd;
 108 }
 109
 110 /* set the events that select waits for on this fd */
 111 void set_select_events( struct object *obj, int events )
 112 {
 113     int user = obj->select;
 114     assert( poll_users[user] == obj );
 115     if (events == -1)  /* stop waiting on this fd completely */
 116     {
 117         pollfd[user].fd = -1;
 118         pollfd[user].events = 0;
 119         pollfd[user].revents = 0;
 120     }
 121     else if (pollfd[user].fd != -1) pollfd[user].events = events;
 122 }
 123
 124 /* check if events are pending */
 125 int check_select_events( int fd, int events )
 126 {
 127     struct pollfd pfd;
 128     pfd.fd     = fd;
 129     pfd.events = events;
 130     return poll( &pfd, 1, 0 ) > 0;
 131 }
 132
 133 /* add a timeout user */
 134 struct timeout_user *add_timeout_user( struct timeval *when, timeout_callback func, void *private )
 135 {
 136     struct timeout_user *user;
 137     struct timeout_user *pos;
 138
 139     if (!(user = mem_alloc( sizeof(*user) ))) return NULL;
 140     user->when     = *when;
 141     user->callback = func;
 142     user->private  = private;
 143
 144     /* Now insert it in the linked list */
 145
 146     for (pos = timeout_head; pos; pos = pos->next)
 147         if (!time_before( &pos->when, when )) break;
 148
 149     if (pos)  /* insert it before 'pos' */
 150     {
 151         if ((user->prev = pos->prev)) user->prev->next = user;
 152         else timeout_head = user;
 153         user->next = pos;
 154         pos->prev = user;
 155     }
 156     else  /* insert it at the tail */
 157     {
 158         user->next = NULL;
 159         if (timeout_tail) timeout_tail->next = user;
 160         else timeout_head = user;
 161         user->prev = timeout_tail;
 162         timeout_tail = user;
 163     }
 164     return user;
 165 }
 166
 167 /* remove a timeout user */
 168 void remove_timeout_user( struct timeout_user *user )
 169 {
 170     if (user->next) user->next->prev = user->prev;
 171     else timeout_tail = user->prev;
 172     if (user->prev) user->prev->next = user->next;
 173     else timeout_head = user->next;
 174     free( user );
 175 }
 176
 177 /* add a timeout in milliseconds to an absolute time */
 178 void add_timeout( struct timeval *when, int timeout )
 179 {
 180     if (timeout)
 181     {
 182         long sec = timeout / 1000;
 183         if ((when->tv_usec += (timeout - 1000*sec) * 1000) >= 1000000)
 184         {
 185             when->tv_usec -= 1000000;
 186             when->tv_sec++;
 187         }
 188         when->tv_sec += sec;
 189     }
 190 }
 191
 192 /* handle the next expired timeout */
 193 static void handle_timeout(void)
 194 {
 195     struct timeout_user *user = timeout_head;
 196     timeout_head = user->next;
 197     if (user->next) user->next->prev = user->prev;
 198     else timeout_tail = user->prev;
 199     user->callback( user->private );
 200     free( user );
 201 }
 202
 203 /* SIGHUP handler */
 204 static void sighup_handler()
 205 {
 206 #ifdef DEBUG_OBJECTS
 207     dump_objects();
 208 #endif
 209 }
 210
 211 /* server main loop */
 212 void select_loop(void)
 213 {
 214     int ret;
 215     sigset_t sigset;
 216     struct sigaction action;
 217
 218     /* block the signals we use */
 219     sigemptyset( &sigset );
 220     sigaddset( &sigset, SIGCHLD );
 221     sigaddset( &sigset, SIGHUP );
 222     sigprocmask( SIG_BLOCK, &sigset, NULL );
 223
 224     /* set the handlers */
 225     action.sa_mask = sigset;
 226     action.sa_flags = 0;
 227     action.sa_handler = sigchld_handler;
 228     sigaction( SIGCHLD, &action, NULL );
 229     action.sa_handler = sighup_handler;
 230     sigaction( SIGHUP, &action, NULL );
 231
 232     while (active_users)
 233     {
 234         long diff = -1;
 235         if (timeout_head)
 236         {
 237             struct timeval now;
 238             gettimeofday( &now, NULL );
 239             while (timeout_head)
 240             {
 241                 if (!time_before( &now, &timeout_head->when )) handle_timeout();
 242                 else
 243                 {
 244                     diff = (timeout_head->when.tv_sec - now.tv_sec) * 1000
 245                             + (timeout_head->when.tv_usec - now.tv_usec) / 1000;
 246                     break;
 247                 }
 248             }
 249         }
 250
 251         sigprocmask( SIG_UNBLOCK, &sigset, NULL );
 252
 253         /* Note: we assume that the signal handlers do not manipulate the pollfd array
 254          *       or the timeout list, otherwise there is a race here.
 255          */
 256         ret = poll( pollfd, nb_users, diff );
 257
 258         sigprocmask( SIG_BLOCK, &sigset, NULL );
 259
 260         if (ret > 0)
 261         {
 262             int i;
 263             for (i = 0; i < nb_users; i++)
 264             {
 265                 if (pollfd[i].revents)
 266                 {
 267                     poll_users[i]->ops->poll_event( poll_users[i], pollfd[i].revents );
 268                     if (!--ret) break;
 269                 }
 270             }
 271         }
 272     }
 273 }