Document QemuEvent to help choose an appropriate synchronization
primitive.

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
---
 include/qemu/thread.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/include/qemu/thread.h b/include/qemu/thread.h
index 573f8c9ede20..f0302ed01fdb 100644
--- a/include/qemu/thread.h
+++ b/include/qemu/thread.h
@@ -10,6 +10,16 @@ typedef struct QemuSemaphore QemuSemaphore;
 typedef struct QemuLockCnt QemuLockCnt;
 typedef struct QemuThread QemuThread;
 
+/*
+ * QemuEvent
+ * =========
+ *
+ * QemuEvent is an implementation of Win32 manual-reset event object.
+ * For details, refer to:
+ * https://learn.microsoft.com/en-us/windows/win32/sync/using-event-objects
+ *
+ * QemuEvent is more lightweight than QemuSemaphore when HAVE_FUTEX is defined.
+ */
 typedef struct QemuEvent {
 #ifndef HAVE_FUTEX
     pthread_mutex_t lock;

-- 
2.49.0