nptl/pthread_key_create.c

   1 /* Copyright (C) 2002-2018 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 "pthreadP.h"
  21 #include <atomic.h>
  22
  23
  24 int
  25 __pthread_key_create (pthread_key_t *key, void (*destr) (void *))
  26 {
  27   /* Find a slot in __pthread_keys which is unused.  */
  28   for (size_t cnt = 0; cnt < PTHREAD_KEYS_MAX; ++cnt)
  29     {
  30       uintptr_t seq = __pthread_keys[cnt].seq;
  31
  32       if (KEY_UNUSED (seq) && KEY_USABLE (seq)
  33           /* We found an unused slot.  Try to allocate it.  */
  34           && ! atomic_compare_and_exchange_bool_acq (&__pthread_keys[cnt].seq,
  35                                                      seq + 1, seq))
  36         {
  37           /* Remember the destructor.  */
  38           __pthread_keys[cnt].destr = destr;
  39
  40           /* Return the key to the caller.  */
  41           *key = cnt;
  42
  43           /* The call succeeded.  */
  44           return 0;
  45         }
  46     }
  47
  48   return EAGAIN;
  49 }
  50 weak_alias (__pthread_key_create, pthread_key_create)
  51 hidden_def (__pthread_key_create)