From: Guillaume Delbergue
Signed-off-by: Guillaume Delbergue
[Rewritten. - Paolo]
Signed-off-by: Paolo Bonzini
[Emilio's additions: use atomic_test_and_set instead of atomic_xchg;
call cpu_relax() while spinning; optimize for uncontended locks by
acquiring the lock with TAS instead of TATAS.]
Signed-off-by: Emilio G. Cota
---
include/qemu/thread.h | 34 ++
1 file changed, 34 insertions(+)
diff --git a/include/qemu/thread.h b/include/qemu/thread.h
index bdae6df..39ff1ac 100644
--- a/include/qemu/thread.h
+++ b/include/qemu/thread.h
@@ -1,6 +1,9 @@
#ifndef __QEMU_THREAD_H
#define __QEMU_THREAD_H 1
+#include
+#include "qemu/processor.h"
+#include "qemu/atomic.h"
typedef struct QemuMutex QemuMutex;
typedef struct QemuCond QemuCond;
@@ -60,4 +63,35 @@ 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)
+{
+spin->value = 0;
+}
+
+static inline void qemu_spin_lock(QemuSpin *spin)
+{
+while (atomic_test_and_set(&spin->value)) {
+while (atomic_read(&spin->value)) {
+cpu_relax();
+}
+}
+}
+
+static inline int qemu_spin_trylock(QemuSpin *spin)
+{
+if (atomic_test_and_set(&spin->value)) {
+return -EBUSY;
+}
+return 0;
+}
+
+static inline void qemu_spin_unlock(QemuSpin *spin)
+{
+atomic_mb_set(&spin->value, 0);
+}
+
#endif
--
2.5.0
