server/semaphore.c

   1 /*
   2  * Server-side semaphore management
   3  *
   4  * Copyright (C) 1998 Alexandre Julliard
   5  */
   6
   7 #include <assert.h>
   8 #include <stdio.h>
   9 #include <stdlib.h>
  10
  11 #include "winerror.h"
  12 #include "winnt.h"
  13 #include "server/thread.h"
  14
  15 struct semaphore
  16 {
  17     struct object  obj;    /* object header */
  18     unsigned int   count;  /* current count */
  19     unsigned int   max;    /* maximum possible count */
  20 };
  21
  22 static void semaphore_dump( struct object *obj, int verbose );
  23 static int semaphore_signaled( struct object *obj, struct thread *thread );
  24 static int semaphore_satisfied( struct object *obj, struct thread *thread );
  25 static void semaphore_destroy( struct object *obj );
  26
  27 static const struct object_ops semaphore_ops =
  28 {
  29     semaphore_dump,
  30     add_queue,
  31     remove_queue,
  32     semaphore_signaled,
  33     semaphore_satisfied,
  34     no_read_fd,
  35     no_write_fd,
  36     no_flush,
  37     no_get_file_info,
  38     semaphore_destroy
  39 };
  40
  41
  42 struct object *create_semaphore( const char *name, unsigned int initial, unsigned int max )
  43 {
  44     struct semaphore *sem;
  45
  46     if (!max || (initial > max))
  47     {
  48         SET_ERROR( ERROR_INVALID_PARAMETER );
  49         return NULL;
  50     }
  51     if (!(sem = (struct semaphore *)create_named_object( name, &semaphore_ops, sizeof(*sem) )))
  52         return NULL;
  53     if (GET_ERROR() != ERROR_ALREADY_EXISTS)
  54     {
  55         /* initialize it if it didn't already exist */
  56         sem->count = initial;
  57         sem->max   = max;
  58     }
  59     return &sem->obj;
  60 }
  61
  62 int open_semaphore( unsigned int access, int inherit, const char *name )
  63 {
  64     return open_object( name, &semaphore_ops, access, inherit );
  65 }
  66
  67 int release_semaphore( int handle, unsigned int count, unsigned int *prev_count )
  68 {
  69     struct semaphore *sem;
  70
  71     if (!(sem = (struct semaphore *)get_handle_obj( current->process, handle,
  72                                                     SEMAPHORE_MODIFY_STATE, &semaphore_ops )))
  73         return 0;
  74
  75     *prev_count = sem->count;
  76     if (sem->count + count < sem->count || sem->count + count > sem->max)
  77     {
  78         SET_ERROR( ERROR_TOO_MANY_POSTS );
  79         return 0;
  80     }
  81     if (sem->count)
  82     {
  83         /* there cannot be any thread waiting if the count is != 0 */
  84         assert( !sem->obj.head );
  85         sem->count += count;
  86     }
  87     else
  88     {
  89         sem->count = count;
  90         wake_up( &sem->obj, count );
  91     }
  92     release_object( sem );
  93     return 1;
  94 }
  95
  96 static void semaphore_dump( struct object *obj, int verbose )
  97 {
  98     struct semaphore *sem = (struct semaphore *)obj;
  99     assert( obj->ops == &semaphore_ops );
 100     fprintf( stderr, "Semaphore count=%d max=%d name='%s'\n",
 101              sem->count, sem->max, get_object_name( &sem->obj ) );
 102 }
 103
 104 static int semaphore_signaled( struct object *obj, struct thread *thread )
 105 {
 106     struct semaphore *sem = (struct semaphore *)obj;
 107     assert( obj->ops == &semaphore_ops );
 108     return (sem->count > 0);
 109 }
 110
 111 static int semaphore_satisfied( struct object *obj, struct thread *thread )
 112 {
 113     struct semaphore *sem = (struct semaphore *)obj;
 114     assert( obj->ops == &semaphore_ops );
 115     assert( sem->count );
 116     sem->count--;
 117     return 0;  /* not abandoned */
 118 }
 119
 120 static void semaphore_destroy( struct object *obj )
 121 {
 122     struct semaphore *sem = (struct semaphore *)obj;
 123     assert( obj->ops == &semaphore_ops );
 124     free( sem );
 125 }