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 <assert.h>
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24
  25 #include "winnt.h"
  26
  27 #include "handle.h"
  28 #include "thread.h"
  29 #include "request.h"
  30
  31 struct semaphore
  32 {
  33     struct object  obj;    /* object header */
  34     unsigned int   count;  /* current count */
  35     unsigned int   max;    /* maximum possible count */
  36 };
  37
  38 static void semaphore_dump( struct object *obj, int verbose );
  39 static int semaphore_signaled( struct object *obj, struct thread *thread );
  40 static int semaphore_satisfied( struct object *obj, struct thread *thread );
  41
  42 static const struct object_ops semaphore_ops =
  43 {
  44     sizeof(struct semaphore),      /* size */
  45     semaphore_dump,                /* dump */
  46     add_queue,                     /* add_queue */
  47     remove_queue,                  /* remove_queue */
  48     semaphore_signaled,            /* signaled */
  49     semaphore_satisfied,           /* satisfied */
  50     NULL,                          /* get_poll_events */
  51     NULL,                          /* poll_event */
  52     no_get_fd,                     /* get_fd */
  53     no_flush,                      /* flush */
  54     no_get_file_info,              /* get_file_info */
  55     NULL,                          /* queue_async */
  56     no_destroy                     /* destroy */
  57 };
  58
  59
  60 static struct semaphore *create_semaphore( const WCHAR *name, size_t len,
  61                                            unsigned int initial, unsigned int max )
  62 {
  63     struct semaphore *sem;
  64
  65     if (!max || (initial > max))
  66     {
  67         set_error( STATUS_INVALID_PARAMETER );
  68         return NULL;
  69     }
  70     if ((sem = create_named_object( &semaphore_ops, name, len )))
  71     {
  72         if (get_error() != STATUS_OBJECT_NAME_COLLISION)
  73         {
  74             /* initialize it if it didn't already exist */
  75             sem->count = initial;
  76             sem->max   = max;
  77         }
  78     }
  79     return sem;
  80 }
  81
  82 static unsigned int release_semaphore( handle_t handle, unsigned int count )
  83 {
  84     struct semaphore *sem;
  85     unsigned int prev = 0;
  86
  87     if ((sem = (struct semaphore *)get_handle_obj( current->process, handle,
  88                                                    SEMAPHORE_MODIFY_STATE, &semaphore_ops )))
  89     {
  90         prev = sem->count;
  91         if (sem->count + count < sem->count || sem->count + count > sem->max)
  92         {
  93             set_error( STATUS_SEMAPHORE_LIMIT_EXCEEDED );
  94         }
  95         else if (sem->count)
  96         {
  97             /* there cannot be any thread waiting if the count is != 0 */
  98             assert( !sem->obj.head );
  99             sem->count += count;
 100         }
 101         else
 102         {
 103             sem->count = count;
 104             wake_up( &sem->obj, count );
 105         }
 106         release_object( sem );
 107     }
 108     return prev;
 109 }
 110
 111 static void semaphore_dump( struct object *obj, int verbose )
 112 {
 113     struct semaphore *sem = (struct semaphore *)obj;
 114     assert( obj->ops == &semaphore_ops );
 115     fprintf( stderr, "Semaphore count=%d max=%d ", sem->count, sem->max );
 116     dump_object_name( &sem->obj );
 117     fputc( '\n', stderr );
 118 }
 119
 120 static int semaphore_signaled( struct object *obj, struct thread *thread )
 121 {
 122     struct semaphore *sem = (struct semaphore *)obj;
 123     assert( obj->ops == &semaphore_ops );
 124     return (sem->count > 0);
 125 }
 126
 127 static int semaphore_satisfied( struct object *obj, struct thread *thread )
 128 {
 129     struct semaphore *sem = (struct semaphore *)obj;
 130     assert( obj->ops == &semaphore_ops );
 131     assert( sem->count );
 132     sem->count--;
 133     return 0;  /* not abandoned */
 134 }
 135
 136 /* create a semaphore */
 137 DECL_HANDLER(create_semaphore)
 138 {
 139     struct semaphore *sem;
 140
 141     reply->handle = 0;
 142     if ((sem = create_semaphore( get_req_data(), get_req_data_size(),
 143                                  req->initial, req->max )))
 144     {
 145         reply->handle = alloc_handle( current->process, sem, SEMAPHORE_ALL_ACCESS, req->inherit );
 146         release_object( sem );
 147     }
 148 }
 149
 150 /* open a handle to a semaphore */
 151 DECL_HANDLER(open_semaphore)
 152 {
 153     reply->handle = open_object( get_req_data(), get_req_data_size(),
 154                                  &semaphore_ops, req->access, req->inherit );
 155 }
 156
 157 /* release a semaphore */
 158 DECL_HANDLER(release_semaphore)
 159 {
 160     reply->prev_count = release_semaphore( req->handle, req->count );
 161 }