On Thu, Jul 23, 2020 at 01:14:10PM +0300, Nikolay Shirokovskiy wrote:
We are dropping the only reference here so that the event loop
thread
is going to be exited synchronously. In order to avoid deadlocks we
need to unlock the VM so that any handler being called can finish
execution and thus even loop thread be finished too.
Signed-off-by: Nikolay Shirokovskiy <nshirokovskiy(a)virtuozzo.com>
---
src/qemu/qemu_domain.c | 18 ++++++++++++++----
1 file changed, 14 insertions(+), 4 deletions(-)
diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index 5b22eb2..82b3d11 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -1637,11 +1637,21 @@ void
qemuDomainObjStopWorker(virDomainObjPtr dom)
{
qemuDomainObjPrivatePtr priv = dom->privateData;
+ virEventThread *eventThread;
- if (priv->eventThread) {
- g_object_unref(priv->eventThread);
- priv->eventThread = NULL;
- }
+ if (!priv->eventThread)
+ return;
+
+ /*
+ * We are dropping the only reference here so that the event loop thread
+ * is going to be exited synchronously. In order to avoid deadlocks we
+ * need to unlock the VM so that any handler being called can finish
+ * execution and thus even loop thread be finished too.
+ */
+ eventThread = g_steal_pointer(&priv->eventThread);
+ virObjectUnlock(dom);
+ g_object_unref(eventThread);
+ virObjectLock(dom);
Hmm, I'm really not at all comfortable with this. I don't have confidence
that qemuProcessStop() safe if we drpo & reacquire the lock half way
through its cleanup process. The 'virDomainObj' is in a semi-clean
state, 1/2 running 1/2 shutoff.
This is the key reason I think I didn't do the synchronous thread join
in the event loop.
Regards,
Daniel
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