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, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include "pthreadP.h"
  20
  21 #ifndef LOCK_PREFIX
  22 # ifdef UP
  23 #  define LOCK_PREFIX   /* nothing */
  24 # else
  25 #  define LOCK_PREFIX   "lock;"
  26 # endif
  27 #endif
  28
  29
  30 int
  31 pthread_spin_lock (lock)
  32      pthread_spinlock_t *lock;
  33 {
  34   asm ("\n"
  35        "1:\t" LOCK_PREFIX "decl %0\n\t"
  36        "jne 2f\n\t"
  37        ".subsection 1\n\t"
  38        ".align 16\n"
  39        "2:\trep; nop\n\t"
  40        "cmpl $0, %0\n\t"
  41        "jg 1b\n\t"
  42        "jmp 2b\n\t"
  43        ".previous"
  44        : "=m" (*lock)
  45        : "m" (*lock));
  46
  47   return 0;
  48 }