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/*
* %CopyrightBegin%
*
* Copyright Ericsson AB 2005-2009. All Rights Reserved.
*
* The contents of this file are subject to the Erlang Public License,
* Version 1.1, (the "License"); you may not use this file except in
* compliance with the License. You should have received a copy of the
* Erlang Public License along with this software. If not, it can be
* retrieved online at http://www.erlang.org/.
*
* Software distributed under the License is distributed on an "AS IS"
* basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
* the License for the specific language governing rights and limitations
* under the License.
*
* %CopyrightEnd%
*/
/*
* Native ethread spinlocks on x86/x86-64.
* Author: Mikael Pettersson.
*/
#ifndef ETHREAD_I386_SPINLOCK_H
#define ETHREAD_I386_SPINLOCK_H
/* A spinlock is the low byte of an aligned 32-bit integer.
* A non-zero value means that the lock is locked.
*/
typedef struct {
volatile unsigned int lock;
} ethr_native_spinlock_t;
#ifdef ETHR_TRY_INLINE_FUNCS
static ETHR_INLINE void
ethr_native_spinlock_init(ethr_native_spinlock_t *lock)
{
lock->lock = 0;
}
static ETHR_INLINE void
ethr_native_spin_unlock(ethr_native_spinlock_t *lock)
{
/* To unlock we move 0 to the lock.
* On i386 this needs to be a locked operation
* to avoid Pentium Pro errata 66 and 92.
*/
#if defined(__x86_64__)
__asm__ __volatile__("" : : : "memory");
*(unsigned char*)&lock->lock = 0;
#else
char tmp = 0;
__asm__ __volatile__(
"xchgb %b0, %1"
: "=q"(tmp), "=m"(lock->lock)
: "0"(tmp) : "memory");
#endif
}
static ETHR_INLINE int
ethr_native_spin_trylock(ethr_native_spinlock_t *lock)
{
char tmp = 1;
__asm__ __volatile__(
"xchgb %b0, %1"
: "=q"(tmp), "=m"(lock->lock)
: "0"(tmp) : "memory");
return tmp == 0;
}
static ETHR_INLINE int
ethr_native_spin_is_locked(ethr_native_spinlock_t *lock)
{
return *(volatile unsigned char*)&lock->lock != 0;
}
static ETHR_INLINE void
ethr_native_spin_lock(ethr_native_spinlock_t *lock)
{
for(;;) {
if (__builtin_expect(ethr_native_spin_trylock(lock) != 0, 1))
break;
do {
__asm__ __volatile__("rep;nop" : "=m"(lock->lock) : : "memory");
} while (ethr_native_spin_is_locked(lock));
}
}
#endif /* ETHR_TRY_INLINE_FUNCS */
#endif /* ETHREAD_I386_SPINLOCK_H */
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