rbd: Don't accept -drive driver=rbd, keyvalue-pairs=...

[mirror_qemu.git] / util / rcu.c

diff --git a/util/rcu.c b/util/rcu.c
index 8ba304dc44118b3295151aebdeb496dd015c66b2..9adc5e4a368ab600d1c53f7076840b51093d9624 100644 (file)
--- a/util/rcu.c
+++ b/util/rcu.c
@@ -26,12 +26,8 @@
  * IBM's contributions to this file may be relicensed under LGPLv2 or later.
  */
 
+#include "qemu/osdep.h"
 #include "qemu-common.h"
-#include <stdio.h>
-#include <assert.h>
-#include <stdlib.h>
-#include <stdint.h>
-#include <errno.h>
 #include "qemu/rcu.h"
 #include "qemu/atomic.h"
 #include "qemu/thread.h"
@@ -86,14 +82,16 @@ static void wait_for_readers(void)
         /* Instead of using atomic_mb_set for index->waiting, and
          * atomic_mb_read for index->ctr, memory barriers are placed
          * manually since writes to different threads are independent.
-         * atomic_mb_set has a smp_wmb before...
+         * qemu_event_reset has acquire semantics, so no memory barrier
+         * is needed here.
          */
-        smp_wmb();
         QLIST_FOREACH(index, &registry, node) {
             atomic_set(&index->waiting, true);
         }
 
-        /* ... and a smp_mb after.  */
+        /* Here, order the stores to index->waiting before the
+         * loads of index->ctr.
+         */
         smp_mb();
 
         QLIST_FOREACH_SAFE(index, &registry, node, tmp) {
@@ -108,9 +106,6 @@ static void wait_for_readers(void)
             }
         }
 
-        /* atomic_mb_read has smp_rmb after.  */
-        smp_rmb();
-
         if (QLIST_EMPTY(&registry)) {
             break;
         }