/usr/lib/erlang/erts-7.3/include/internal/i386/spinlock.h is in erlang-dev 1:18.3-dfsg-1ubuntu3.
This file is owned by root:root, with mode 0o644.
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* %CopyrightBegin%
*
* Copyright Ericsson AB 2005-2011. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions 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
#define ETHR_HAVE_NATIVE_SPINLOCKS 1
#define ETHR_NATIVE_SPINLOCK_IMPL "ethread"
/* 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;
#if defined(ETHR_TRY_INLINE_FUNCS) || defined(ETHR_AUX_IMPL__)
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__)
if (ETHR_X86_RUNTIME_CONF_HAVE_NO_SSE2__) {
char tmp = 0;
__asm__ __volatile__(
"xchgb %b0, %1"
: "=q"(tmp), "=m"(lock->lock)
: "0"(tmp) : "memory");
}
else
#endif
{
ETHR_MEMBAR(ETHR_LoadStore|ETHR_StoreStore);
*(unsigned char*)&lock->lock = 0;
}
}
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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