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_close_handle,               /* close_handle */
  57     no_destroy                     /* destroy */
  58 };
  59
  60
  61 static struct semaphore *create_semaphore( const WCHAR *name, size_t len,
  62                                            unsigned int initial, unsigned int max )
  63 {
  64     struct semaphore *sem;
  65
  66     if (!max || (initial > max))
  67     {
  68         set_error( STATUS_INVALID_PARAMETER );
  69         return NULL;
  70     }
  71     if ((sem = create_named_object( sync_namespace, &semaphore_ops, name, len )))
  72     {
  73         if (get_error() != STATUS_OBJECT_NAME_COLLISION)
  74         {
  75             /* initialize it if it didn't already exist */
  76             sem->count = initial;
  77             sem->max   = max;
  78         }
  79     }
  80     return sem;
  81 }
  82
  83 static int release_semaphore( struct semaphore *sem, unsigned int count,
  84                               unsigned int *prev )
  85 {
  86     if (prev) *prev = sem->count;
  87     if (sem->count + count < sem->count || sem->count + count > sem->max)
  88     {
  89         set_error( STATUS_SEMAPHORE_LIMIT_EXCEEDED );
  90         return 0;
  91     }
  92     else if (sem->count)
  93     {
  94         /* there cannot be any thread to wake up if the count is != 0 */
  95         sem->count += count;
  96     }
  97     else
  98     {
  99         sem->count = count;
 100         wake_up( &sem->obj, count );
 101     }
 102     return 1;
 103 }
 104
 105 static void semaphore_dump( struct object *obj, int verbose )
 106 {
 107     struct semaphore *sem = (struct semaphore *)obj;
 108     assert( obj->ops == &semaphore_ops );
 109     fprintf( stderr, "Semaphore count=%d max=%d ", sem->count, sem->max );
 110     dump_object_name( &sem->obj );
 111     fputc( '\n', stderr );
 112 }
 113
 114 static int semaphore_signaled( struct object *obj, struct thread *thread )
 115 {
 116     struct semaphore *sem = (struct semaphore *)obj;
 117     assert( obj->ops == &semaphore_ops );
 118     return (sem->count > 0);
 119 }
 120
 121 static int semaphore_satisfied( struct object *obj, struct thread *thread )
 122 {
 123     struct semaphore *sem = (struct semaphore *)obj;
 124     assert( obj->ops == &semaphore_ops );
 125     assert( sem->count );
 126     sem->count--;
 127     return 0;  /* not abandoned */
 128 }
 129
 130 static int semaphore_signal( struct object *obj, unsigned int access )
 131 {
 132     struct semaphore *sem = (struct semaphore *)obj;
 133     assert( obj->ops == &semaphore_ops );
 134
 135     if (!(access & SEMAPHORE_MODIFY_STATE))
 136     {
 137         set_error( STATUS_ACCESS_DENIED );
 138         return 0;
 139     }
 140     return release_semaphore( sem, 1, NULL );
 141 }
 142
 143 /* create a semaphore */
 144 DECL_HANDLER(create_semaphore)
 145 {
 146     struct semaphore *sem;
 147
 148     reply->handle = 0;
 149     if ((sem = create_semaphore( get_req_data(), get_req_data_size(),
 150                                  req->initial, req->max )))
 151     {
 152         reply->handle = alloc_handle( current->process, sem, req->access, req->inherit );
 153         release_object( sem );
 154     }
 155 }
 156
 157 /* open a handle to a semaphore */
 158 DECL_HANDLER(open_semaphore)
 159 {
 160     reply->handle = open_object( sync_namespace, get_req_data(), get_req_data_size(),
 161                                  &semaphore_ops, req->access, req->inherit );
 162 }
 163
 164 /* release a semaphore */
 165 DECL_HANDLER(release_semaphore)
 166 {
 167     struct semaphore *sem;
 168
 169     if ((sem = (struct semaphore *)get_handle_obj( current->process, req->handle,
 170                                                    SEMAPHORE_MODIFY_STATE, &semaphore_ops )))
 171     {
 172         release_semaphore( sem, req->count, &reply->prev_count );
 173         release_object( sem );
 174     }
 175 }