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 "ntstatus.h"
  30 #define WIN32_NO_STATUS
  31 #include "windef.h"
  32 #include "winternl.h"
  33
  34 #include "handle.h"
  35 #include "thread.h"
  36 #include "request.h"
  37
  38 struct semaphore
  39 {
  40     struct object  obj;    /* object header */
  41     unsigned int   count;  /* current count */
  42     unsigned int   max;    /* maximum possible count */
  43 };
  44
  45 static void semaphore_dump( struct object *obj, int verbose );
  46 static int semaphore_signaled( struct object *obj, struct thread *thread );
  47 static int semaphore_satisfied( struct object *obj, struct thread *thread );
  48 static int semaphore_signal( struct object *obj, unsigned int access );
  49
  50 static const struct object_ops semaphore_ops =
  51 {
  52     sizeof(struct semaphore),      /* size */
  53     semaphore_dump,                /* dump */
  54     add_queue,                     /* add_queue */
  55     remove_queue,                  /* remove_queue */
  56     semaphore_signaled,            /* signaled */
  57     semaphore_satisfied,           /* satisfied */
  58     semaphore_signal,              /* signal */
  59     no_get_fd,                     /* get_fd */
  60     no_lookup_name,                /* lookup_name */
  61     no_close_handle,               /* close_handle */
  62     no_destroy                     /* destroy */
  63 };
  64
  65
  66 static struct semaphore *create_semaphore( const struct unicode_str *name, unsigned int attr,
  67                                            unsigned int initial, unsigned int max )
  68 {
  69     struct semaphore *sem;
  70
  71     if (!max || (initial > max))
  72     {
  73         set_error( STATUS_INVALID_PARAMETER );
  74         return NULL;
  75     }
  76     if ((sem = create_named_object( sync_namespace, &semaphore_ops, name, attr )))
  77     {
  78         if (get_error() != STATUS_OBJECT_NAME_EXISTS)
  79         {
  80             /* initialize it if it didn't already exist */
  81             sem->count = initial;
  82             sem->max   = max;
  83         }
  84     }
  85     return sem;
  86 }
  87
  88 static int release_semaphore( struct semaphore *sem, unsigned int count,
  89                               unsigned int *prev )
  90 {
  91     if (prev) *prev = sem->count;
  92     if (sem->count + count < sem->count || sem->count + count > sem->max)
  93     {
  94         set_error( STATUS_SEMAPHORE_LIMIT_EXCEEDED );
  95         return 0;
  96     }
  97     else if (sem->count)
  98     {
  99         /* there cannot be any thread to wake up if the count is != 0 */
 100         sem->count += count;
 101     }
 102     else
 103     {
 104         sem->count = count;
 105         wake_up( &sem->obj, count );
 106     }
 107     return 1;
 108 }
 109
 110 static void semaphore_dump( struct object *obj, int verbose )
 111 {
 112     struct semaphore *sem = (struct semaphore *)obj;
 113     assert( obj->ops == &semaphore_ops );
 114     fprintf( stderr, "Semaphore count=%d max=%d ", sem->count, sem->max );
 115     dump_object_name( &sem->obj );
 116     fputc( '\n', stderr );
 117 }
 118
 119 static int semaphore_signaled( struct object *obj, struct thread *thread )
 120 {
 121     struct semaphore *sem = (struct semaphore *)obj;
 122     assert( obj->ops == &semaphore_ops );
 123     return (sem->count > 0);
 124 }
 125
 126 static int semaphore_satisfied( struct object *obj, struct thread *thread )
 127 {
 128     struct semaphore *sem = (struct semaphore *)obj;
 129     assert( obj->ops == &semaphore_ops );
 130     assert( sem->count );
 131     sem->count--;
 132     return 0;  /* not abandoned */
 133 }
 134
 135 static int semaphore_signal( struct object *obj, unsigned int access )
 136 {
 137     struct semaphore *sem = (struct semaphore *)obj;
 138     assert( obj->ops == &semaphore_ops );
 139
 140     if (!(access & SEMAPHORE_MODIFY_STATE))
 141     {
 142         set_error( STATUS_ACCESS_DENIED );
 143         return 0;
 144     }
 145     return release_semaphore( sem, 1, NULL );
 146 }
 147
 148 /* create a semaphore */
 149 DECL_HANDLER(create_semaphore)
 150 {
 151     struct semaphore *sem;
 152     struct unicode_str name;
 153
 154     reply->handle = 0;
 155     get_req_unicode_str( &name );
 156     if ((sem = create_semaphore( &name, req->attributes, req->initial, req->max )))
 157     {
 158         reply->handle = alloc_handle( current->process, sem, req->access,
 159                                       req->attributes & OBJ_INHERIT );
 160         release_object( sem );
 161     }
 162 }
 163
 164 /* open a handle to a semaphore */
 165 DECL_HANDLER(open_semaphore)
 166 {
 167     struct unicode_str name;
 168
 169     get_req_unicode_str( &name );
 170     reply->handle = open_object( sync_namespace, &name, &semaphore_ops, req->access, req->attributes );
 171 }
 172
 173 /* release a semaphore */
 174 DECL_HANDLER(release_semaphore)
 175 {
 176     struct semaphore *sem;
 177
 178     if ((sem = (struct semaphore *)get_handle_obj( current->process, req->handle,
 179                                                    SEMAPHORE_MODIFY_STATE, &semaphore_ops )))
 180     {
 181         release_semaphore( sem, req->count, &reply->prev_count );
 182         release_object( sem );
 183     }
 184 }