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