server/semaphore.c

   1 /*
   2  * Server-side semaphore management
   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 "config.h"
  22 #include "wine/port.h"
  23
  24 #include <assert.h>
  25 #include <stdio.h>
  26 #include <stdlib.h>
  27
  28 #include "windef.h"
  29
  30 #include "handle.h"
  31 #include "thread.h"
  32 #include "request.h"
  33
  34 struct semaphore
  35 {
  36     struct object  obj;    /* object header */
  37     unsigned int   count;  /* current count */
  38     unsigned int   max;    /* maximum possible count */
  39 };
  40
  41 static void semaphore_dump( struct object *obj, int verbose );
  42 static int semaphore_signaled( struct object *obj, struct thread *thread );
  43 static int semaphore_satisfied( struct object *obj, struct thread *thread );
  44
  45 static const struct object_ops semaphore_ops =
  46 {
  47     sizeof(struct semaphore),      /* size */
  48     semaphore_dump,                /* dump */
  49     add_queue,                     /* add_queue */
  50     remove_queue,                  /* remove_queue */
  51     semaphore_signaled,            /* signaled */
  52     semaphore_satisfied,           /* satisfied */
  53     no_get_fd,                     /* get_fd */
  54     no_destroy                     /* destroy */
  55 };
  56
  57
  58 static struct semaphore *create_semaphore( const WCHAR *name, size_t len,
  59                                            unsigned int initial, unsigned int max )
  60 {
  61     struct semaphore *sem;
  62
  63     if (!max || (initial > max))
  64     {
  65         set_error( STATUS_INVALID_PARAMETER );
  66         return NULL;
  67     }
  68     if ((sem = create_named_object( sync_namespace, &semaphore_ops, name, len )))
  69     {
  70         if (get_error() != STATUS_OBJECT_NAME_COLLISION)
  71         {
  72             /* initialize it if it didn't already exist */
  73             sem->count = initial;
  74             sem->max   = max;
  75         }
  76     }
  77     return sem;
  78 }
  79
  80 static unsigned int release_semaphore( obj_handle_t handle, unsigned int count )
  81 {
  82     struct semaphore *sem;
  83     unsigned int prev = 0;
  84
  85     if ((sem = (struct semaphore *)get_handle_obj( current->process, handle,
  86                                                    SEMAPHORE_MODIFY_STATE, &semaphore_ops )))
  87     {
  88         prev = sem->count;
  89         if (sem->count + count < sem->count || sem->count + count > sem->max)
  90         {
  91             set_error( STATUS_SEMAPHORE_LIMIT_EXCEEDED );
  92         }
  93         else if (sem->count)
  94         {
  95             /* there cannot be any thread to wake up if the count is != 0 */
  96             sem->count += count;
  97         }
  98         else
  99         {
 100             sem->count = count;
 101             wake_up( &sem->obj, count );
 102         }
 103         release_object( sem );
 104     }
 105     return prev;
 106 }
 107
 108 static void semaphore_dump( struct object *obj, int verbose )
 109 {
 110     struct semaphore *sem = (struct semaphore *)obj;
 111     assert( obj->ops == &semaphore_ops );
 112     fprintf( stderr, "Semaphore count=%d max=%d ", sem->count, sem->max );
 113     dump_object_name( &sem->obj );
 114     fputc( '\n', stderr );
 115 }
 116
 117 static int semaphore_signaled( struct object *obj, struct thread *thread )
 118 {
 119     struct semaphore *sem = (struct semaphore *)obj;
 120     assert( obj->ops == &semaphore_ops );
 121     return (sem->count > 0);
 122 }
 123
 124 static int semaphore_satisfied( struct object *obj, struct thread *thread )
 125 {
 126     struct semaphore *sem = (struct semaphore *)obj;
 127     assert( obj->ops == &semaphore_ops );
 128     assert( sem->count );
 129     sem->count--;
 130     return 0;  /* not abandoned */
 131 }
 132
 133 /* create a semaphore */
 134 DECL_HANDLER(create_semaphore)
 135 {
 136     struct semaphore *sem;
 137
 138     reply->handle = 0;
 139     if ((sem = create_semaphore( get_req_data(), get_req_data_size(),
 140                                  req->initial, req->max )))
 141     {
 142         reply->handle = alloc_handle( current->process, sem, req->access, req->inherit );
 143         release_object( sem );
 144     }
 145 }
 146
 147 /* open a handle to a semaphore */
 148 DECL_HANDLER(open_semaphore)
 149 {
 150     reply->handle = open_object( sync_namespace, get_req_data(), get_req_data_size(),
 151                                  &semaphore_ops, req->access, req->inherit );
 152 }
 153
 154 /* release a semaphore */
 155 DECL_HANDLER(release_semaphore)
 156 {
 157     reply->prev_count = release_semaphore( req->handle, req->count );
 158 }