[PATCH 1/1] monitor: don't wake up qmp_dispatcher_co coroutine upon cleanup

[andrey . drobyshev]

From: Andrey Drobyshev <andrey.drobys...@virtuozzo.com>

Since the commit 3e6bed61 ("monitor: cleanup detection of qmp_dispatcher_co
shutting down"), coroutine pointer qmp_dispatcher_co is set to NULL upon
cleanup.  If a QMP command is sent after monitor_cleanup() (e.g. after
shutdown), this may lead to SEGFAULT on aio_co_wake(NULL).

As mentioned in the comment inside monitor_cleanup(), the intention is to
allow incoming requests while shutting down, but simply leave them
without any response.  Let's do exactly that, and if qmp_dispatcher_co
coroutine pointer has already been set to NULL, let's simply skip the
aio_co_wake() part.

Signed-off-by: Andrey Drobyshev <andrey.drobys...@virtuozzo.com>
---
 monitor/qmp.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/monitor/qmp.c b/monitor/qmp.c
index 2f46cf9e49..cb99a12d94 100644
--- a/monitor/qmp.c
+++ b/monitor/qmp.c
@@ -356,7 +356,8 @@ void qmp_dispatcher_co_wake(void)
     /* Write request before reading qmp_dispatcher_co_busy.  */
     smp_mb__before_rmw();
 
-    if (!qatomic_xchg(&qmp_dispatcher_co_busy, true)) {
+    if (!qatomic_xchg(&qmp_dispatcher_co_busy, true) &&
+            qatomic_read(&qmp_dispatcher_co)) {
         aio_co_wake(qmp_dispatcher_co);
     }
 }
-- 
2.43.5