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 #include "winternl.h"
  30
  31 #include "handle.h"
  32 #include "thread.h"
  33 #include "request.h"
  34
  35 struct semaphore
  36 {
  37     struct object  obj;    /* object header */
  38     unsigned int   count;  /* current count */
  39     unsigned int   max;    /* maximum possible count */
  40 };
  41
  42 static void semaphore_dump( struct object *obj, int verbose );
  43 static int semaphore_signaled( struct object *obj, struct thread *thread );
  44 static int semaphore_satisfied( struct object *obj, struct thread *thread );
  45 static int semaphore_signal( struct object *obj, unsigned int access );
  46
  47 static const struct object_ops semaphore_ops =
  48 {
  49     sizeof(struct semaphore),      /* size */
  50     semaphore_dump,                /* dump */
  51     add_queue,                     /* add_queue */
  52     remove_queue,                  /* remove_queue */
  53     semaphore_signaled,            /* signaled */
  54     semaphore_satisfied,           /* satisfied */
  55     semaphore_signal,              /* signal */
  56     no_get_fd,                     /* get_fd */
  57     no_close_handle,               /* close_handle */
  58     no_destroy                     /* destroy */
  59 };
  60
  61
  62 static struct semaphore *create_semaphore( const WCHAR *name, size_t len, unsigned int attr,
  63                                            unsigned int initial, unsigned int max )
  64 {
  65     struct semaphore *sem;
  66
  67     if (!max || (initial > max))
  68     {
  69         set_error( STATUS_INVALID_PARAMETER );
  70         return NULL;
  71     }
  72     if ((sem = create_named_object( sync_namespace, &semaphore_ops, name, len, attr )))
  73     {
  74         if (get_error() != STATUS_OBJECT_NAME_COLLISION)
  75         {
  76             /* initialize it if it didn't already exist */
  77             sem->count = initial;
  78             sem->max   = max;
  79         }
  80     }
  81     return sem;
  82 }
  83
  84 static int release_semaphore( struct semaphore *sem, unsigned int count,
  85                               unsigned int *prev )
  86 {
  87     if (prev) *prev = sem->count;
  88     if (sem->count + count < sem->count || sem->count + count > sem->max)
  89     {
  90         set_error( STATUS_SEMAPHORE_LIMIT_EXCEEDED );
  91         return 0;
  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     return 1;
 104 }
 105
 106 static void semaphore_dump( struct object *obj, int verbose )
 107 {
 108     struct semaphore *sem = (struct semaphore *)obj;
 109     assert( obj->ops == &semaphore_ops );
 110     fprintf( stderr, "Semaphore count=%d max=%d ", sem->count, sem->max );
 111     dump_object_name( &sem->obj );
 112     fputc( '\n', stderr );
 113 }
 114
 115 static int semaphore_signaled( struct object *obj, struct thread *thread )
 116 {
 117     struct semaphore *sem = (struct semaphore *)obj;
 118     assert( obj->ops == &semaphore_ops );
 119     return (sem->count > 0);
 120 }
 121
 122 static int semaphore_satisfied( struct object *obj, struct thread *thread )
 123 {
 124     struct semaphore *sem = (struct semaphore *)obj;
 125     assert( obj->ops == &semaphore_ops );
 126     assert( sem->count );
 127     sem->count--;
 128     return 0;  /* not abandoned */
 129 }
 130
 131 static int semaphore_signal( struct object *obj, unsigned int access )
 132 {
 133     struct semaphore *sem = (struct semaphore *)obj;
 134     assert( obj->ops == &semaphore_ops );
 135
 136     if (!(access & SEMAPHORE_MODIFY_STATE))
 137     {
 138         set_error( STATUS_ACCESS_DENIED );
 139         return 0;
 140     }
 141     return release_semaphore( sem, 1, NULL );
 142 }
 143
 144 /* create a semaphore */
 145 DECL_HANDLER(create_semaphore)
 146 {
 147     struct semaphore *sem;
 148
 149     reply->handle = 0;
 150     if ((sem = create_semaphore( get_req_data(), get_req_data_size(), req->attributes,
 151                                  req->initial, req->max )))
 152     {
 153         reply->handle = alloc_handle( current->process, sem, req->access,
 154                                       req->attributes & OBJ_INHERIT );
 155         release_object( sem );
 156     }
 157 }
 158
 159 /* open a handle to a semaphore */
 160 DECL_HANDLER(open_semaphore)
 161 {
 162     reply->handle = open_object( sync_namespace, get_req_data(), get_req_data_size(),
 163                                  &semaphore_ops, req->access, req->attributes );
 164 }
 165
 166 /* release a semaphore */
 167 DECL_HANDLER(release_semaphore)
 168 {
 169     struct semaphore *sem;
 170
 171     if ((sem = (struct semaphore *)get_handle_obj( current->process, req->handle,
 172                                                    SEMAPHORE_MODIFY_STATE, &semaphore_ops )))
 173     {
 174         release_semaphore( sem, req->count, &reply->prev_count );
 175         release_object( sem );
 176     }
 177 }