util/defer-call: move defer_call() to util/

[mirror_qemu.git] / util / qemu-coroutine-lock.c

diff --git a/util/qemu-coroutine-lock.c b/util/qemu-coroutine-lock.c
index 45c6b57374b4f8469f60e23c633bde763c0a89ac..2534435388f3dce83de34d5f8a7f0594294975d3 100644 (file)
--- a/util/qemu-coroutine-lock.c
+++ b/util/qemu-coroutine-lock.c
@@ -27,7 +27,6 @@
  */
 
 #include "qemu/osdep.h"
-#include "qemu/coroutine.h"
 #include "qemu/coroutine_int.h"
 #include "qemu/processor.h"
 #include "qemu/queue.h"
@@ -202,10 +201,16 @@ static void coroutine_fn qemu_co_mutex_lock_slowpath(AioContext *ctx,
     trace_qemu_co_mutex_lock_entry(mutex, self);
     push_waiter(mutex, &w);
 
+    /*
+     * Add waiter before reading mutex->handoff.  Pairs with qatomic_set_mb
+     * in qemu_co_mutex_unlock.
+     */
+    smp_mb__after_rmw();
+
     /* This is the "Responsibility Hand-Off" protocol; a lock() picks from
      * a concurrent unlock() the responsibility of waking somebody up.
      */
-    old_handoff = qatomic_mb_read(&mutex->handoff);
+    old_handoff = qatomic_read(&mutex->handoff);
     if (old_handoff &&
         has_waiters(mutex) &&
         qatomic_cmpxchg(&mutex->handoff, old_handoff, 0) == old_handoff) {
@@ -304,7 +309,8 @@ void coroutine_fn qemu_co_mutex_unlock(CoMutex *mutex)
         }
 
         our_handoff = mutex->sequence;
-        qatomic_mb_set(&mutex->handoff, our_handoff);
+        /* Set handoff before checking for waiters.  */
+        qatomic_set_mb(&mutex->handoff, our_handoff);
         if (!has_waiters(mutex)) {
             /* The concurrent lock has not added itself yet, so it
              * will be able to pick our handoff.