[libvirt] [PATCH v2 2/3] qemu: first wait all workers finish on state cleanup

[Nikolay Shirokovskiy]

On 27.10.2016 16:00, John Ferlan wrote:
> 
> 
> On 10/04/2016 10:27 AM, Nikolay Shirokovskiy wrote:
>> This fix the crash [1]
>>
>> This happens on race conditions of simultaneous exiting libvirtd and qemu process.
>> Let's just finish all workers that keep driver pointer before disposing
>> driver object or any of its members.
>>
>> [1] crash backtrace: (bt is shortened a bit):
> 
> Before pushing I'll reword the above just a little bit for readability
> 
>>
>> 0  0x00007ffff7282f2b in virClassIsDerivedFrom (klass=0xdeadbeef, parent=0x55555581d650) at util/virobject.c:169
>> 1  0x00007ffff72835fd in virObjectIsClass (anyobj=0x7fffd024f580, klass=0x55555581d650) at util/virobject.c:365
>> 2  0x00007ffff7283498 in virObjectLock (anyobj=0x7fffd024f580) at util/virobject.c:317
>> 3  0x00007ffff722f0a3 in virCloseCallbacksUnset (closeCallbacks=0x7fffd024f580, vm=0x7fffd0194db0,
>>     cb=0x7fffdf1af765 <qemuProcessAutoDestroy>) at util/virclosecallbacks.c:164
>> 4  0x00007fffdf1afa7b in qemuProcessAutoDestroyRemove (driver=0x7fffd00f3a60, vm=0x7fffd0194db0)
>>     at qemu/qemu_process.c:6365
>> 5  0x00007fffdf1adff1 in qemuProcessStop (driver=0x7fffd00f3a60, vm=0x7fffd0194db0,
>>     reason=VIR_DOMAIN_SHUTOFF_CRASHED, asyncJob=QEMU_ASYNC_JOB_NONE, flags=0) at qemu/qemu_process.c:5877
>> 6  0x00007fffdf1f711c in processMonitorEOFEvent (driver=0x7fffd00f3a60, vm=0x7fffd0194db0)
>>     at qemu/qemu_driver.c:4545
>> 7  0x00007fffdf1f7313 in qemuProcessEventHandler (data=0x555555832710, opaque=0x7fffd00f3a60)
>>     at qemu/qemu_driver.c:4589
>> 8  0x00007ffff72a84c4 in virThreadPoolWorker (opaque=0x555555805da0) at util/virthreadpool.c:167
>>
>> Thread 1 (Thread 0x7ffff7fb1880 (LWP 494472)):
>> 1  0x00007ffff72a7898 in virCondWait (c=0x7fffd01c21f8, m=0x7fffd01c21a0) at util/virthread.c:154
>> 2  0x00007ffff72a8a22 in virThreadPoolFree (pool=0x7fffd01c2160) at util/virthreadpool.c:290
>> 3  0x00007fffdf1edd44 in qemuStateCleanup () at qemu/qemu_driver.c:1102
>> 4  0x00007ffff736570a in virStateCleanup () at libvirt.c:807
>> 5  0x000055555556f991 in main (argc=1, argv=0x7fffffffe458) at libvirtd.c:1660
>> ---
>>  src/qemu/qemu_driver.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
>> index 12ddbc0..58753ea 100644
>> --- a/src/qemu/qemu_driver.c
>> +++ b/src/qemu/qemu_driver.c
>> @@ -1068,6 +1068,7 @@ qemuStateCleanup(void)
>>      if (!qemu_driver)
>>          return -1;
>>  
>> +    virThreadPoolFree(qemu_driver->workerPool);
> 
> For this one - your thoughts on swapping the order to be
> NWFilterUnRegister and ThreadPoolFree(workerPool)?
> 
> Nothing in the NW filter call back jumps out at me as generating a
> workerPool job, but since the order of Initialization is workerPool,
> then NWFilterCallbackRegister I figure the order to Cleanup should just
> be inversed.

Looks like these two are independent... So we can use any order and 
cleaning up in reverse order to initializing is probably good style.

> 
> ACK  for what's here, but I'll await yours or any other feedback on
> swapping before pushing.
> 
> John
> 
>>      virNWFilterUnRegisterCallbackDriver(&qemuCallbackDriver);
>>      virObjectUnref(qemu_driver->config);
>>      virObjectUnref(qemu_driver->hostdevMgr);
>> @@ -1099,7 +1100,6 @@ qemuStateCleanup(void)
>>      virLockManagerPluginUnref(qemu_driver->lockManager);
>>  
>>      virMutexDestroy(&qemu_driver->lock);
>> -    virThreadPoolFree(qemu_driver->workerPool);
>>      VIR_FREE(qemu_driver);
>>  
>>      return 0;
>>