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