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 "winnt.h"
  12
  13 #include "handle.h"
  14 #include "thread.h"
  15 #include "request.h"
  16
  17 struct semaphore
  18 {
  19     struct object  obj;    /* object header */
  20     unsigned int   count;  /* current count */
  21     unsigned int   max;    /* maximum possible count */
  22 };
  23
  24 static void semaphore_dump( struct object *obj, int verbose );
  25 static int semaphore_signaled( struct object *obj, struct thread *thread );
  26 static int semaphore_satisfied( struct object *obj, struct thread *thread );
  27
  28 static const struct object_ops semaphore_ops =
  29 {
  30     sizeof(struct semaphore),      /* size */
  31     semaphore_dump,                /* dump */
  32     add_queue,                     /* add_queue */
  33     remove_queue,                  /* remove_queue */
  34     semaphore_signaled,            /* signaled */
  35     semaphore_satisfied,           /* satisfied */
  36     NULL,                          /* get_poll_events */
  37     NULL,                          /* poll_event */
  38     no_read_fd,                    /* get_read_fd */
  39     no_write_fd,                   /* get_write_fd */
  40     no_flush,                      /* flush */
  41     no_get_file_info,              /* get_file_info */
  42     no_destroy                     /* destroy */
  43 };
  44
  45
  46 static struct semaphore *create_semaphore( const WCHAR *name, size_t len,
  47                                            unsigned int initial, unsigned int max )
  48 {
  49     struct semaphore *sem;
  50
  51     if (!max || (initial > max))
  52     {
  53         set_error( STATUS_INVALID_PARAMETER );
  54         return NULL;
  55     }
  56     if ((sem = create_named_object( &semaphore_ops, name, len )))
  57     {
  58         if (get_error() != STATUS_OBJECT_NAME_COLLISION)
  59         {
  60             /* initialize it if it didn't already exist */
  61             sem->count = initial;
  62             sem->max   = max;
  63         }
  64     }
  65     return sem;
  66 }
  67
  68 static unsigned int release_semaphore( int handle, unsigned int count )
  69 {
  70     struct semaphore *sem;
  71     unsigned int prev = 0;
  72
  73     if ((sem = (struct semaphore *)get_handle_obj( current->process, handle,
  74                                                    SEMAPHORE_MODIFY_STATE, &semaphore_ops )))
  75     {
  76         prev = sem->count;
  77         if (sem->count + count < sem->count || sem->count + count > sem->max)
  78         {
  79             set_error( STATUS_SEMAPHORE_LIMIT_EXCEEDED );
  80         }
  81         else 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     }
  94     return prev;
  95 }
  96
  97 static void semaphore_dump( struct object *obj, int verbose )
  98 {
  99     struct semaphore *sem = (struct semaphore *)obj;
 100     assert( obj->ops == &semaphore_ops );
 101     fprintf( stderr, "Semaphore count=%d max=%d ", sem->count, sem->max );
 102     dump_object_name( &sem->obj );
 103     fputc( '\n', stderr );
 104 }
 105
 106 static int semaphore_signaled( struct object *obj, struct thread *thread )
 107 {
 108     struct semaphore *sem = (struct semaphore *)obj;
 109     assert( obj->ops == &semaphore_ops );
 110     return (sem->count > 0);
 111 }
 112
 113 static int semaphore_satisfied( struct object *obj, struct thread *thread )
 114 {
 115     struct semaphore *sem = (struct semaphore *)obj;
 116     assert( obj->ops == &semaphore_ops );
 117     assert( sem->count );
 118     sem->count--;
 119     return 0;  /* not abandoned */
 120 }
 121
 122 /* create a semaphore */
 123 DECL_HANDLER(create_semaphore)
 124 {
 125     size_t len = get_req_strlenW( req, req->name );
 126     struct semaphore *sem;
 127
 128     req->handle = -1;
 129     if ((sem = create_semaphore( req->name, len, req->initial, req->max )))
 130     {
 131         req->handle = alloc_handle( current->process, sem, SEMAPHORE_ALL_ACCESS, req->inherit );
 132         release_object( sem );
 133     }
 134 }
 135
 136 /* open a handle to a semaphore */
 137 DECL_HANDLER(open_semaphore)
 138 {
 139     size_t len = get_req_strlenW( req, req->name );
 140     req->handle = open_object( req->name, len, &semaphore_ops, req->access, req->inherit );
 141 }
 142
 143 /* release a semaphore */
 144 DECL_HANDLER(release_semaphore)
 145 {
 146     req->prev_count = release_semaphore( req->handle, req->count );
 147 }