[libvirt] [PATCH 4/4] qemu: first wait all workers finish on state cleanup

[Nikolay Shirokovskiy]

This fix next crash (bt is shortened a bit):

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

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.
---
 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 e29180d..30a2830 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);
     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;
-- 
1.8.3.1