nptl/pthread_getspecific.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 <stdlib.h>
  20 #include "pthreadP.h"
  21
  22
  23 void *
  24 __pthread_getspecific (pthread_key_t key)
  25 {
  26   struct pthread_key_data *data;
  27
  28   /* Special case access to the first 2nd-level block.  This is the
  29      usual case.  */
  30   if (__glibc_likely (key < PTHREAD_KEY_2NDLEVEL_SIZE))
  31     data = &THREAD_SELF->specific_1stblock[key];
  32   else
  33     {
  34       /* Verify the key is sane.  */
  35       if (key >= PTHREAD_KEYS_MAX)
  36         /* Not valid.  */
  37         return NULL;
  38
  39       unsigned int idx1st = key / PTHREAD_KEY_2NDLEVEL_SIZE;
  40       unsigned int idx2nd = key % PTHREAD_KEY_2NDLEVEL_SIZE;
  41
  42       /* If the sequence number doesn't match or the key cannot be defined
  43          for this thread since the second level array is not allocated
  44          return NULL, too.  */
  45       struct pthread_key_data *level2 = THREAD_GETMEM_NC (THREAD_SELF,
  46                                                           specific, idx1st);
  47       if (level2 == NULL)
  48         /* Not allocated, therefore no data.  */
  49         return NULL;
  50
  51       /* There is data.  */
  52       data = &level2[idx2nd];
  53     }
  54
  55   void *result = data->data;
  56   if (result != NULL)
  57     {
  58       uintptr_t seq = data->seq;
  59
  60       if (__glibc_unlikely (seq != __pthread_keys[key].seq))
  61         result = data->data = NULL;
  62     }
  63
  64   return result;
  65 }
  66 weak_alias (__pthread_getspecific, pthread_getspecific)
  67 hidden_def (__pthread_getspecific)