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

[John Ferlan]

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.

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;
>