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/* Machine-dependent pthreads configuration and inline functions.
i386 version.
Copyright (C) 1996, 1997, 1998 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Richard Henderson <rth@tamu.edu>.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If not,
write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
/* Spinlock implementation; required. */
extern inline int
testandset (int *spinlock)
{
int ret;
__asm__ __volatile__("xchgl %0, %1"
: "=r"(ret), "=m"(*spinlock)
: "0"(1), "m"(*spinlock));
return ret;
}
/* Get some notion of the current stack. Need not be exactly the top
of the stack, just something somewhere in the current frame. */
#define CURRENT_STACK_FRAME stack_pointer
register char * stack_pointer __asm__ ("%esp");
/* Compare-and-swap for semaphores.
Available on the 486 and above, but not on the 386.
We test dynamically whether it's available or not. */
#define HAS_COMPARE_AND_SWAP
#ifndef __i686__
# define TEST_FOR_COMPARE_AND_SWAP
#endif
extern inline int
__compare_and_swap (long int *p, long int oldval, long int newval)
{
char ret;
long int readval;
__asm__ __volatile__ ("lock; cmpxchgl %3, %1; sete %0"
: "=q" (ret), "=m" (*p), "=a" (readval)
: "r" (newval), "m" (*p), "a" (oldval));
return ret;
}
extern inline int
get_eflags (void)
{
int res;
__asm__ __volatile__ ("pushfl; popl %0" : "=r" (res) : );
return res;
}
extern inline void
set_eflags (int newflags)
{
__asm__ __volatile__ ("pushl %0; popfl" : : "r" (newflags) : "cc");
}
extern inline int
compare_and_swap_is_available (void)
{
int oldflags = get_eflags ();
int changed;
/* Flip AC bit in EFLAGS. */
set_eflags (oldflags ^ 0x40000);
/* See if bit changed. */
changed = (get_eflags () ^ oldflags) & 0x40000;
/* Restore EFLAGS. */
set_eflags (oldflags);
/* If the AC flag did not change, it's a 386 and it lacks cmpxchg.
Otherwise, it's a 486 or above and it has cmpxchg. */
return changed != 0;
}
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