Re: [libvirt] [Question]Libvirt doesn't care about qemu monitor event if fail to destroy qemu process

5 Mar 2018

Thanks,
Zongyong Wu
...
-----Original Message-----
From: Michal Privoznik [mailto:mprivozn@redhat.com]
Sent: Monday, March 05, 2018 5:27 PM
To: Wuzongyong (Euler Dept) <cordius.wu@huawei.com>; libvir-
list@redhat.com
Cc: Wanzongshun (Vincent) <wanzongshun@huawei.com>; weijinfen
<weijinfen@huawei.com>
Subject: Re: [libvirt] [Question]Libvirt doesn't care about qemu monitor
event if fail to destroy qemu process
...
Hi,
We unregister qemu monitor after sending QEMU_PROCESS_EVENT_MONITOR_EOF
to workerPool:
static void
qemuProcessHandleMonitorEOF(qemuMonitorPtr mon,
                            virDomainObjPtr vm,
                            void *opaque) {
    virQEMUDriverPtr driver = opaque;
    qemuDomainObjPrivatePtr priv;
struct qemuProcessEvent *processEvent; ...
processEvent->eventType = QEMU_PROCESS_EVENT_MONITOR_EOF;
    processEvent->vm = vm;
virObjectRef(vm);
    if (virThreadPoolSendJob(driver->workerPool, 0, processEvent) < 0) {
        ignore_value(virObjectUnref(vm));
        VIR_FREE(processEvent);
        goto cleanup;
    }
/* We don't want this EOF handler to be called over and over while
On 03/05/2018 03:20 AM, Wuzongyong (Euler Dept) wrote:
the
...
* thread is waiting for a job.
     */
qemuMonitorUnregister(mon);
...
}
Then we handle QEMU_PROCESS_EVENT_MONITOR_EOF in processMonitorEOFEvent
function:
...
static void
processMonitorEOFEvent(virQEMUDriverPtr driver,
                       virDomainObjPtr vm) {
      ...
      if (qemuProcessBeginStopJob(driver, vm, QEMU_JOB_DESTROY, true) <
0)
...
return;
      ...
}
Here,  libvirt will show that the vm state is running all the time if
qemuProcessBeginStopJob return -1 even though qemu may terminate or be
killed later.
...
So, may be we should re-register the monitor when
qemuProcessBeginStopJob failed?
The fact that processMonitorEOFEvent() failed to grab DESTROY job means
that we screwed up earlier and now you're just seeing effects of it.
Threads should be albe to acquire DESTROY job at any point, regardless of
other jobs set on the domain object.
Can you please:
a) try to turn on debug logs [1] and tell us why acquiring DESTROY job
failed? You should see an error message like this:
error: cannot acquire state change lock ..
b) tell us what is your libvirt version and if you're able to reproduce
this with the latest git HEAD?
I said " qemuProcessBeginStopJob failed" means that：
we failed to kill qemu process in 15 seconds (refer to virProcessKillPainfully).
IOW, we send SIGTERM and SIGKILL but the qemu process doesn't exit in 15s， and
then libvirt will think qemu is still in running state event though qemu  exit
indeed after the 15s loop in virProcessKillPainfully.

int
qemuProcessBeginStopJob(virQEMUDriverPtr driver,
                        virDomainObjPtr vm,
                        qemuDomainJob job,
                        bool forceKill)
{
	...
	if (qemuProcessKill(vm, killFlags) < 0)
        goto cleanup;
	...
}
...
Ha! Looking at the code I think I've found something that might be causing
this issue. Do you have max_queued set in qemu.conf? Because if you do,
then qemuDomainObjBeginJobInternal() might fail to set job because it's
above the set limit. If I'm right, this should be the fix:

diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c index
8b4efc82d..7eb631e06 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -5401,7 +5401,8 @@ qemuDomainObjBeginJobInternal(virQEMUDriverPtr
driver,
     then = now + QEMU_JOB_WAIT_TIME;
retry:
-    if (cfg->maxQueuedJobs &&
+    if ((!async && job == QEMU_JOB_DESTROY) &&
+        cfg->maxQueuedJobs &&
         priv->jobs_queued > cfg->maxQueuedJobs) {
         goto error;
     }
Michal


    