aio_notify can be optimized away, and in fact almost always will. However,
qemu_notify_event is used in places where this is incorrect---most notably,
when handling SIGTERM. When aio_notify is optimized away, it is possible that
QEMU enters a blocking ppoll immediately afterwards and stays there, without
reaching main_loop_should_exit().
Fix this by using a bottom half. The bottom half can be optimized too, but
it will cause the ppoll not to block. The hang is thus avoided.
Reported-by: Peter Maydell <peter.mayd...@linaro.org>
Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
---
main-loop.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/main-loop.c b/main-loop.c
index 82875a4..9d93478 100644
--- a/main-loop.c
+++ b/main-loop.c
@@ -114,6 +114,11 @@ static int qemu_signal_init(void)
#endif
static AioContext *qemu_aio_context;
+static QEMUBH *qemu_notify_bh;
+
+static void notify_event_cb(void *opaque)
+{
+}
AioContext *qemu_get_aio_context(void)
{
@@ -125,7 +130,7 @@ void qemu_notify_event(void)
if (!qemu_aio_context) {
return;
}
- aio_notify(qemu_aio_context);
+ qemu_bh_schedule(qemu_notify_bh);
}
static GArray *gpollfds;
@@ -144,6 +149,7 @@ int qemu_init_main_loop(Error **errp)
}
qemu_aio_context = aio_context_new(&local_error);
+ qemu_notify_bh = qemu_bh_new(notify_event_cb, NULL);
if (!qemu_aio_context) {
error_propagate(errp, local_error);
return -EMFILE;
--
2.4.3
