libpthread/nptl/pthread_key_create.c

   1 /* Copyright (C) 2002, 2003, 2006 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 attribute_protected
  26 __pthread_key_create (
  27      pthread_key_t *key,
  28      void (*destr) (void *))
  29 {
  30   /* Find a slot in __pthread_kyes which is unused.  */
  31   size_t cnt;
  32   for (cnt = 0; cnt < PTHREAD_KEYS_MAX; ++cnt)
  33     {
  34       uintptr_t seq = __pthread_keys[cnt].seq;
  35
  36       if (KEY_UNUSED (seq) && KEY_USABLE (seq)
  37           /* We found an unused slot.  Try to allocate it.  */
  38           && ! atomic_compare_and_exchange_bool_acq (&__pthread_keys[cnt].seq,
  39                                                      seq + 1, seq))
  40         {
  41           /* Remember the destructor.  */
  42           __pthread_keys[cnt].destr = destr;
  43
  44           /* Return the key to the caller.  */
  45           *key = cnt;
  46
  47           /* The call succeeded.  */
  48           return 0;
  49         }
  50     }
  51
  52   return EAGAIN;
  53 }
  54 strong_alias (__pthread_key_create, pthread_key_create)
  55 strong_alias (__pthread_key_create, __pthread_key_create_internal)