Merge remote-tracking branch 'remotes/stefanha/tags/block-pull-request' into staging

Pull request

v2:
 * v1 emails 2/3 and 3/3 weren't sent due to an email failure
 * Included Sergio's updated wording in the commit description

# gpg: Signature made Wed 08 Nov 2017 19:12:01 GMT
# gpg:                using RSA key 0x9CA4ABB381AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>"
# gpg:                 aka "Stefan Hajnoczi <stefanha@gmail.com>"
# Primary key fingerprint: 8695 A8BF D3F9 7CDA AC35  775A 9CA4 ABB3 81AB 73C8

* remotes/stefanha/tags/block-pull-request:
  util/async: use atomic_mb_set in qemu_bh_cancel
  tests-aio-multithread: fix /aio/multi/schedule race condition

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

2 files changed, 3 insertions, 4 deletions

diff --git a/tests/test-aio-multithread.c b/tests/test-aio-multithread.c
index 549d784915..d396185972 100644
--- a/tests/test-aio-multithread.c
+++ b/tests/test-aio-multithread.c
@@ -144,17 +144,16 @@ static void finish_cb(void *opaque)
 static coroutine_fn void test_multi_co_schedule_entry(void *opaque)
 {
     g_assert(to_schedule[id] == NULL);
-    atomic_mb_set(&to_schedule[id], qemu_coroutine_self());
 
     while (!atomic_mb_read(&now_stopping)) {
         int n;
 
         n = g_test_rand_int_range(0, NUM_CONTEXTS);
         schedule_next(n);
-        qemu_coroutine_yield();
 
-        g_assert(to_schedule[id] == NULL);
         atomic_mb_set(&to_schedule[id], qemu_coroutine_self());
+        qemu_coroutine_yield();
+        g_assert(to_schedule[id] == NULL);
     }
 }
 
diff --git a/util/async.c b/util/async.c
index 355af73ee7..0e1bd8780a 100644
--- a/util/async.c
+++ b/util/async.c
@@ -174,7 +174,7 @@ void qemu_bh_schedule(QEMUBH *bh)
  */
 void qemu_bh_cancel(QEMUBH *bh)
 {
-    bh->scheduled = 0;
+    atomic_mb_set(&bh->scheduled, 0);
 }
 
 /* This func is async.The bottom half will do the delete action at the finial