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qemu-thread: add simple test-and-set spinlock

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Reviewed-by: Sergey Fedorov <sergey.fedorov@linaro.org>
Signed-off-by: Guillaume Delbergue <guillaume.delbergue@greensocs.com>
[Rewritten. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
[Emilio's additions: use TAS instead of atomic_xchg; emit acquire/release
 barriers; return bool from trylock; call cpu_relax() while spinning;
 optimize for uncontended locks by acquiring the lock with TAS instead
 of TATAS; add qemu_spin_locked().]
Signed-off-by: Emilio G. Cota <cota@braap.org>
Message-Id: <1465412133-3029-6-git-send-email-cota@braap.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>
This commit is contained in:
Guillaume Delbergue 2016-06-08 14:55:23 -04:00 committed by Richard Henderson
parent 462cda505f
commit ac9a9eba1e
1 changed files with 35 additions and 0 deletions
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35
include/qemu/thread.h
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@ -1,6 +1,8 @@
#ifndef __QEMU_THREAD_H
#define __QEMU_THREAD_H 1
#include "qemu/processor.h"
#include "qemu/atomic.h"
typedef struct QemuMutex QemuMutex;
typedef struct QemuCond QemuCond;
@ -60,4 +62,37 @@ struct Notifier;
void qemu_thread_atexit_add(struct Notifier *notifier);
void qemu_thread_atexit_remove(struct Notifier *notifier);
typedef struct QemuSpin {
int value;
} QemuSpin;
static inline void qemu_spin_init(QemuSpin *spin)
{
__sync_lock_release(&spin->value);
}
static inline void qemu_spin_lock(QemuSpin *spin)
{
while (unlikely(__sync_lock_test_and_set(&spin->value, true))) {
while (atomic_read(&spin->value)) {
cpu_relax();
}
}
}
static inline bool qemu_spin_trylock(QemuSpin *spin)
{
return __sync_lock_test_and_set(&spin->value, true);
}
static inline bool qemu_spin_locked(QemuSpin *spin)
{
return atomic_read(&spin->value);
}
static inline void qemu_spin_unlock(QemuSpin *spin)
{
__sync_lock_release(&spin->value);
}
#endif