nptl/sem_close.c

   1 /* Copyright (C) 2002-2020 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    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <search.h>
  21 #include <sys/mman.h>
  22 #include "semaphoreP.h"
  23
  24 struct walk_closure
  25 {
  26   sem_t *the_sem;
  27   struct inuse_sem *rec;
  28 };
  29
  30 static void
  31 walker (const void *inodep, VISIT which, void *closure0)
  32 {
  33   struct walk_closure *closure = closure0;
  34   struct inuse_sem *nodep = *(struct inuse_sem **) inodep;
  35
  36   if (nodep->sem == closure->the_sem)
  37     closure->rec = nodep;
  38 }
  39
  40
  41 int
  42 sem_close (sem_t *sem)
  43 {
  44   int result = 0;
  45
  46   /* Get the lock.  */
  47   lll_lock (__sem_mappings_lock, LLL_PRIVATE);
  48
  49   /* Locate the entry for the mapping the caller provided.  */
  50   struct inuse_sem *rec;
  51   {
  52     struct walk_closure closure = { .the_sem = sem, .rec = NULL };
  53     __twalk_r (__sem_mappings, walker, &closure);
  54     rec = closure.rec;
  55   }
  56   if  (rec != NULL)
  57     {
  58       /* Check the reference counter.  If it is going to be zero, free
  59          all the resources.  */
  60       if (--rec->refcnt == 0)
  61         {
  62           /* Remove the record from the tree.  */
  63           (void) __tdelete (rec, &__sem_mappings, __sem_search);
  64
  65           result = munmap (rec->sem, sizeof (sem_t));
  66
  67           free (rec);
  68         }
  69     }
  70   else
  71     {
  72       /* This is no valid semaphore.  */
  73       result = -1;
  74       __set_errno (EINVAL);
  75     }
  76
  77   /* Release the lock.  */
  78   lll_unlock (__sem_mappings_lock, LLL_PRIVATE);
  79
  80   return result;
  81 }