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 static int semaphore_signal( struct object *obj, unsigned int access );
  45
  46 static const struct object_ops semaphore_ops =
  47 {
  48     sizeof(struct semaphore),      /* size */
  49     semaphore_dump,                /* dump */
  50     add_queue,                     /* add_queue */
  51     remove_queue,                  /* remove_queue */
  52     semaphore_signaled,            /* signaled */
  53     semaphore_satisfied,           /* satisfied */
  54     semaphore_signal,              /* signal */
  55     no_get_fd,                     /* get_fd */
  56     no_destroy                     /* destroy */
  57 };
  58
  59
  60 static struct semaphore *create_semaphore( const WCHAR *name, size_t len,
  61                                            unsigned int initial, unsigned int max )
  62 {
  63     struct semaphore *sem;
  64
  65     if (!max || (initial > max))
  66     {
  67         set_error( STATUS_INVALID_PARAMETER );
  68         return NULL;
  69     }
  70     if ((sem = create_named_object( sync_namespace, &semaphore_ops, name, len )))
  71     {
  72         if (get_error() != STATUS_OBJECT_NAME_COLLISION)
  73         {
  74             /* initialize it if it didn't already exist */
  75             sem->count = initial;
  76             sem->max   = max;
  77         }
  78     }
  79     return sem;
  80 }
  81
  82 static int release_semaphore( struct semaphore *sem, unsigned int count,
  83                               unsigned int *prev )
  84 {
  85     if (prev) *prev = sem->count;
  86     if (sem->count + count < sem->count || sem->count + count > sem->max)
  87     {
  88         set_error( STATUS_SEMAPHORE_LIMIT_EXCEEDED );
  89         return 0;
  90     }
  91     else if (sem->count)
  92     {
  93         /* there cannot be any thread to wake up if the count is != 0 */
  94         sem->count += count;
  95     }
  96     else
  97     {
  98         sem->count = count;
  99         wake_up( &sem->obj, count );
 100     }
 101     return 1;
 102 }
 103
 104 static void semaphore_dump( struct object *obj, int verbose )
 105 {
 106     struct semaphore *sem = (struct semaphore *)obj;
 107     assert( obj->ops == &semaphore_ops );
 108     fprintf( stderr, "Semaphore count=%d max=%d ", sem->count, sem->max );
 109     dump_object_name( &sem->obj );
 110     fputc( '\n', stderr );
 111 }
 112
 113 static int semaphore_signaled( struct object *obj, struct thread *thread )
 114 {
 115     struct semaphore *sem = (struct semaphore *)obj;
 116     assert( obj->ops == &semaphore_ops );
 117     return (sem->count > 0);
 118 }
 119
 120 static int semaphore_satisfied( struct object *obj, struct thread *thread )
 121 {
 122     struct semaphore *sem = (struct semaphore *)obj;
 123     assert( obj->ops == &semaphore_ops );
 124     assert( sem->count );
 125     sem->count--;
 126     return 0;  /* not abandoned */
 127 }
 128
 129 static int semaphore_signal( struct object *obj, unsigned int access )
 130 {
 131     struct semaphore *sem = (struct semaphore *)obj;
 132     assert( obj->ops == &semaphore_ops );
 133
 134     if (!(access & SEMAPHORE_MODIFY_STATE))
 135     {
 136         set_error( STATUS_ACCESS_DENIED );
 137         return 0;
 138     }
 139     return release_semaphore( sem, 1, NULL );
 140 }
 141
 142 /* create a semaphore */
 143 DECL_HANDLER(create_semaphore)
 144 {
 145     struct semaphore *sem;
 146
 147     reply->handle = 0;
 148     if ((sem = create_semaphore( get_req_data(), get_req_data_size(),
 149                                  req->initial, req->max )))
 150     {
 151         reply->handle = alloc_handle( current->process, sem, req->access, req->inherit );
 152         release_object( sem );
 153     }
 154 }
 155
 156 /* open a handle to a semaphore */
 157 DECL_HANDLER(open_semaphore)
 158 {
 159     reply->handle = open_object( sync_namespace, get_req_data(), get_req_data_size(),
 160                                  &semaphore_ops, req->access, req->inherit );
 161 }
 162
 163 /* release a semaphore */
 164 DECL_HANDLER(release_semaphore)
 165 {
 166     struct semaphore *sem;
 167
 168     if ((sem = (struct semaphore *)get_handle_obj( current->process, req->handle,
 169                                                    SEMAPHORE_MODIFY_STATE, &semaphore_ops )))
 170     {
 171         release_semaphore( sem, req->count, &reply->prev_count );
 172         release_object( sem );
 173     }
 174 }