[Qemu-devel] [PATCH v2] throttle-groups: update tg->any_timer_armed[] on detach

[Stefan Hajnoczi <stefanha@redhat.com>]

Clear tg->any_timer_armed[] when throttling timers are destroyed during
AioContext attach/detach.  Failure to do so causes throttling to hang
because we believe the timer is already scheduled!

The following was broken at least since QEMU 2.10.0 with -drive
iops=100:

  $ dd if=/dev/zero of=/dev/vdb oflag=direct count=1000
  (qemu) stop
  (qemu) cont
  ...I/O is stuck...

Reported-by: Yongxue Hong <yhong@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
v2:
 * Use timer_pending(tt->timers[i]) instead of token [Berto]
 * Fix s/destroy/destroyed/ typo [Eric]

 block/throttle-groups.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/block/throttle-groups.c b/block/throttle-groups.c
index 6ba992c8d7..0a49f3c409 100644
--- a/block/throttle-groups.c
+++ b/block/throttle-groups.c
@@ -592,6 +592,17 @@ void throttle_group_attach_aio_context(ThrottleGroupMember *tgm,
 void throttle_group_detach_aio_context(ThrottleGroupMember *tgm)
 {
     ThrottleTimers *tt = &tgm->throttle_timers;
+    ThrottleGroup *tg = container_of(tgm->throttle_state, ThrottleGroup, ts);
+
+    qemu_mutex_lock(&tg->lock);
+    if (timer_pending(tt->timers[0])) {
+        tg->any_timer_armed[0] = false;
+    }
+    if (timer_pending(tt->timers[1])) {
+        tg->any_timer_armed[1] = false;
+    }
+    qemu_mutex_unlock(&tg->lock);
+
     throttle_timers_detach_aio_context(tt);
     tgm->aio_context = NULL;
 }
-- 
2.13.5