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glibc  2.9
pthread_spin_lock.c
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00001 /* Copyright (C) 2003, 2004 Free Software Foundation, Inc.
00002    This file is part of the GNU C Library.
00003    Contributed by Jakub Jelinek <jakub@redhat.com>, 2003.
00004 
00005    The GNU C Library is free software; you can redistribute it and/or
00006    modify it under the terms of the GNU Lesser General Public
00007    License as published by the Free Software Foundation; either
00008    version 2.1 of the License, or (at your option) any later version.
00009 
00010    The GNU C Library is distributed in the hope that it will be useful,
00011    but WITHOUT ANY WARRANTY; without even the implied warranty of
00012    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00013    Lesser General Public License for more details.
00014 
00015    You should have received a copy of the GNU Lesser General Public
00016    License along with the GNU C Library; if not, write to the Free
00017    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00018    02111-1307 USA.  */
00019 
00020 #include "pthreadP.h"
00021 
00022 int
00023 pthread_spin_lock (lock)
00024      pthread_spinlock_t *lock;
00025 {
00026   int *p = (int *) lock;
00027 
00028   while (__builtin_expect (__sync_val_compare_and_swap (p, 0, 1), 0))
00029     {
00030       /* Spin without using the atomic instruction.  */
00031       do
00032        __asm __volatile ("hint @pause" : : : "memory");
00033       while (*p);
00034     }
00035   return 0;
00036 }