nptl/sem_close.c

   1 /* Copyright (C) 2002-2017 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <search.h>
  21 #include <sys/mman.h>
  22 #include "semaphoreP.h"
  23
  24
  25 /* Global variables to parametrize the walk function.  This works
  26    since we always have to use locks.  And we have to use the twalk
  27    function since the entries are not sorted wrt the mapping
  28    address.  */
  29 static sem_t *the_sem;
  30 static struct inuse_sem *rec;
  31
  32 static void
  33 walker (const void *inodep, const VISIT which, const int depth)
  34 {
  35   struct inuse_sem *nodep = *(struct inuse_sem **) inodep;
  36
  37   if (nodep->sem == the_sem)
  38     rec = nodep;
  39 }
  40
  41
  42 int
  43 sem_close (sem_t *sem)
  44 {
  45   int result = 0;
  46
  47   /* Get the lock.  */
  48   lll_lock (__sem_mappings_lock, LLL_PRIVATE);
  49
  50   /* Locate the entry for the mapping the caller provided.  */
  51   rec = NULL;
  52   the_sem = sem;
  53   __twalk (__sem_mappings, walker);
  54   if  (rec != NULL)
  55     {
  56       /* Check the reference counter.  If it is going to be zero, free
  57          all the resources.  */
  58       if (--rec->refcnt == 0)
  59         {
  60           /* Remove the record from the tree.  */
  61           (void) __tdelete (rec, &__sem_mappings, __sem_search);
  62
  63           result = munmap (rec->sem, sizeof (sem_t));
  64
  65           free (rec);
  66         }
  67     }
  68   else
  69     {
  70       /* This is no valid semaphore.  */
  71       result = -1;
  72       __set_errno (EINVAL);
  73     }
  74
  75   /* Release the lock.  */
  76   lll_unlock (__sem_mappings_lock, LLL_PRIVATE);
  77
  78   return result;
  79 }