linuxthreads/sysdeps/i386/i686/pt-machine.h

   1 /* Machine-dependent pthreads configuration and inline functions.
   2    i686 version.
   3    Copyright (C) 1996-2001, 2002, 2003 Free Software Foundation, Inc.
   4    This file is part of the GNU C Library.
   5    Contributed by Richard Henderson <rth@tamu.edu>.
   6
   7    The GNU C Library is free software; you can redistribute it and/or
   8    modify it under the terms of the GNU Lesser General Public License as
   9    published by the Free Software Foundation; either version 2.1 of the
  10    License, or (at your option) any later version.
  11
  12    The GNU C Library is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15    Lesser General Public License for more details.
  16
  17    You should have received a copy of the GNU Lesser General Public
  18    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  19    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  20    Boston, MA 02111-1307, USA.  */
  21
  22 #ifndef _PT_MACHINE_H
  23 #define _PT_MACHINE_H   1
  24
  25 #ifndef PT_EI
  26 # define PT_EI extern inline __attribute__ ((always_inline))
  27 #endif
  28 #include "kernel-features.h"
  29
  30 #ifndef __ASSEMBLER__
  31 extern long int testandset (int *spinlock);
  32 extern int __compare_and_swap (long int *p, long int oldval, long int newval);
  33
  34 /* Get some notion of the current stack.  Need not be exactly the top
  35    of the stack, just something somewhere in the current frame.  */
  36 #define CURRENT_STACK_FRAME  __builtin_frame_address (0)
  37
  38
  39 /* Spinlock implementation; required.  */
  40 PT_EI long int
  41 testandset (int *spinlock)
  42 {
  43   long int ret;
  44
  45   __asm__ __volatile__ (
  46         "xchgl %0, %1"
  47         : "=r" (ret), "=m" (*spinlock)
  48         : "0" (1), "m" (*spinlock)
  49         : "memory");
  50
  51   return ret;
  52 }
  53
  54
  55 /* Compare-and-swap for semaphores.  It's always available on i686.  */
  56 #define HAS_COMPARE_AND_SWAP
  57
  58 PT_EI int
  59 __compare_and_swap (long int *p, long int oldval, long int newval)
  60 {
  61   char ret;
  62   long int readval;
  63
  64   __asm__ __volatile__ ("lock; cmpxchgl %3, %1; sete %0"
  65                         : "=q" (ret), "=m" (*p), "=a" (readval)
  66                         : "r" (newval), "m" (*p), "a" (oldval)
  67                         : "memory");
  68   return ret;
  69 }
  70 #endif
  71
  72 #if __ASSUME_LDT_WORKS > 0
  73 #include "../useldt.h"
  74 #endif
  75
  76 /* The P4 and above really want some help to prevent overheating.  */
  77 #define BUSY_WAIT_NOP   __asm__ ("rep; nop")
  78
  79 #endif /* pt-machine.h */