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

   1 /* Machine-dependent pthreads configuration and inline functions.
   2    i686 version.
   3    Copyright (C) 1996-2001, 2002 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 Library General Public License as
   9    published by the Free Software Foundation; either version 2 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    Library General Public License for more details.
  16
  17    You should have received a copy of the GNU Library 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
  27 #endif
  28 #include "kernel-features.h"
  29
  30 /* Get some notion of the current stack.  Need not be exactly the top
  31    of the stack, just something somewhere in the current frame.  */
  32 #define CURRENT_STACK_FRAME  __builtin_frame_address (0)
  33
  34
  35 /* Spinlock implementation; required.  */
  36 PT_EI long int
  37 testandset (int *spinlock)
  38 {
  39   long int ret;
  40
  41   __asm__ __volatile__ (
  42         "xchgl %0, %1"
  43         : "=r" (ret), "=m" (*spinlock)
  44         : "0" (1), "m" (*spinlock)
  45         : "memory");
  46
  47   return ret;
  48 }
  49
  50
  51 /* Compare-and-swap for semaphores.  It's always available on i686.  */
  52 #define HAS_COMPARE_AND_SWAP
  53
  54 PT_EI int
  55 __compare_and_swap (long int *p, long int oldval, long int newval)
  56 {
  57   char ret;
  58   long int readval;
  59
  60   __asm__ __volatile__ ("lock; cmpxchgl %3, %1; sete %0"
  61                         : "=q" (ret), "=m" (*p), "=a" (readval)
  62                         : "r" (newval), "m" (*p), "a" (oldval)
  63                         : "memory");
  64   return ret;
  65 }
  66
  67 #if __ASSUME_LDT_WORKS > 0
  68 #include "../useldt.h"
  69 #endif
  70
  71 /* The P4 and above really want some help to prevent overheating.  */
  72 #define BUSY_WAIT_NOP   __asm__ ("rep; nop")
  73
  74 #endif /* pt-machine.h */