From: Guillaume Delbergue <guillaume.delber...@greensocs.com>
Signed-off-by: Guillaume Delbergue <guillaume.delber...@greensocs.com>
[Rewritten. - Paolo]
Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
[Emilio's additions: call cpu_relax() while spinning; optimize for
uncontended locks by acquiring the lock with test-and-set instead of
test-and-test-and-set.]
Signed-off-by: Emilio G. Cota <c...@braap.org>
---
include/qemu/thread.h | 34 ++++++++++++++++++++++++++++++++++
1 file changed, 34 insertions(+)
diff --git a/include/qemu/thread.h b/include/qemu/thread.h
index bdae6df..a216941 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 <errno.h>
+#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_xchg(&spin->value, true)) {
+ while (atomic_read(&spin->value)) {
+ cpu_relax();
+ }
+ }
+}
+
+static inline int qemu_spin_trylock(QemuSpin *spin)
+{
+ if (atomic_xchg(&spin->value, true)) {
+ return -EBUSY;
+ }
+ return 0;
+}
+
+static inline void qemu_spin_unlock(QemuSpin *spin)
+{
+ atomic_mb_set(&spin->value, 0);
+}
+
#endif
--
2.5.0
