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 #include <stdarg.h>
  28
  29 #include "windef.h"
  30 #include "winternl.h"
  31
  32 #include "handle.h"
  33 #include "thread.h"
  34 #include "request.h"
  35
  36 struct semaphore
  37 {
  38     struct object  obj;    /* object header */
  39     unsigned int   count;  /* current count */
  40     unsigned int   max;    /* maximum possible count */
  41 };
  42
  43 static void semaphore_dump( struct object *obj, int verbose );
  44 static int semaphore_signaled( struct object *obj, struct thread *thread );
  45 static int semaphore_satisfied( struct object *obj, struct thread *thread );
  46 static int semaphore_signal( struct object *obj, unsigned int access );
  47
  48 static const struct object_ops semaphore_ops =
  49 {
  50     sizeof(struct semaphore),      /* size */
  51     semaphore_dump,                /* dump */
  52     add_queue,                     /* add_queue */
  53     remove_queue,                  /* remove_queue */
  54     semaphore_signaled,            /* signaled */
  55     semaphore_satisfied,           /* satisfied */
  56     semaphore_signal,              /* signal */
  57     no_get_fd,                     /* get_fd */
  58     no_lookup_name,                /* lookup_name */
  59     no_close_handle,               /* close_handle */
  60     no_destroy                     /* destroy */
  61 };
  62
  63
  64 static struct semaphore *create_semaphore( const struct unicode_str *name, unsigned int attr,
  65                                            unsigned int initial, unsigned int max )
  66 {
  67     struct semaphore *sem;
  68
  69     if (!max || (initial > max))
  70     {
  71         set_error( STATUS_INVALID_PARAMETER );
  72         return NULL;
  73     }
  74     if ((sem = create_named_object( sync_namespace, &semaphore_ops, name, attr )))
  75     {
  76         if (get_error() != STATUS_OBJECT_NAME_EXISTS)
  77         {
  78             /* initialize it if it didn't already exist */
  79             sem->count = initial;
  80             sem->max   = max;
  81         }
  82     }
  83     return sem;
  84 }
  85
  86 static int release_semaphore( struct semaphore *sem, unsigned int count,
  87                               unsigned int *prev )
  88 {
  89     if (prev) *prev = sem->count;
  90     if (sem->count + count < sem->count || sem->count + count > sem->max)
  91     {
  92         set_error( STATUS_SEMAPHORE_LIMIT_EXCEEDED );
  93         return 0;
  94     }
  95     else if (sem->count)
  96     {
  97         /* there cannot be any thread to wake up if the count is != 0 */
  98         sem->count += count;
  99     }
 100     else
 101     {
 102         sem->count = count;
 103         wake_up( &sem->obj, count );
 104     }
 105     return 1;
 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 static int semaphore_signal( struct object *obj, unsigned int access )
 134 {
 135     struct semaphore *sem = (struct semaphore *)obj;
 136     assert( obj->ops == &semaphore_ops );
 137
 138     if (!(access & SEMAPHORE_MODIFY_STATE))
 139     {
 140         set_error( STATUS_ACCESS_DENIED );
 141         return 0;
 142     }
 143     return release_semaphore( sem, 1, NULL );
 144 }
 145
 146 /* create a semaphore */
 147 DECL_HANDLER(create_semaphore)
 148 {
 149     struct semaphore *sem;
 150     struct unicode_str name;
 151
 152     reply->handle = 0;
 153     get_req_unicode_str( &name );
 154     if ((sem = create_semaphore( &name, req->attributes, req->initial, req->max )))
 155     {
 156         reply->handle = alloc_handle( current->process, sem, req->access,
 157                                       req->attributes & OBJ_INHERIT );
 158         release_object( sem );
 159     }
 160 }
 161
 162 /* open a handle to a semaphore */
 163 DECL_HANDLER(open_semaphore)
 164 {
 165     struct unicode_str name;
 166
 167     get_req_unicode_str( &name );
 168     reply->handle = open_object( sync_namespace, &name, &semaphore_ops, req->access, req->attributes );
 169 }
 170
 171 /* release a semaphore */
 172 DECL_HANDLER(release_semaphore)
 173 {
 174     struct semaphore *sem;
 175
 176     if ((sem = (struct semaphore *)get_handle_obj( current->process, req->handle,
 177                                                    SEMAPHORE_MODIFY_STATE, &semaphore_ops )))
 178     {
 179         release_semaphore( sem, req->count, &reply->prev_count );
 180         release_object( sem );
 181     }
 182 }