nptl/sysdeps/i386/pthread_spin_lock.c

   1 /* Copyright (C) 2002,2003,2004 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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include "pthreadP.h"
  21
  22 #ifndef LOCK_PREFIX
  23 # ifdef UP
  24 #  define LOCK_PREFIX   /* nothing */
  25 # else
  26 #  define LOCK_PREFIX   "lock;"
  27 # endif
  28 #endif
  29
  30
  31 int
  32 pthread_spin_lock (lock)
  33      pthread_spinlock_t *lock;
  34 {
  35   asm ("\n"
  36        "1:\t" LOCK_PREFIX "decl %0\n\t"
  37        "jne 2f\n\t"
  38        ".subsection 1\n\t"
  39        ".align 16\n"
  40        "2:\trep; nop\n\t"
  41        "cmpl $0, %0\n\t"
  42        "jg 1b\n\t"
  43        "jmp 2b\n\t"
  44        ".previous"
  45        : "=m" (*lock)
  46        : "m" (*lock));
  47
  48   return 0;
  49 }