[libvirt] [PATCH] qemu: Fix segmentation fault on reconnect

[Marc Hartmayer]

On start up of libvirtd the worker pool of the QEMU driver must be
initialized before trying to reconnect to all the running QEMU
instances. Otherwise segmentation faults can occur if there are QEMU
monitor events emitted.

 #0  __GI___pthread_mutex_lock (mutex=mutex at entry=0x40) at ../nptl/pthread_mutex_lock.c:67
 #1  0x000003fffdba9e62 in virMutexLock (m=m at entry=0x40) at ../../src/util/virthread.c:89
 #2  0x000003fffdbab2dc in virThreadPoolSendJob (pool=0x0, priority=priority at entry=0, jobData=0x1000b7210) at ../../src/util/virthreadpool.c:386
 #3  0x000003ffd8343b70 in qemuProcessHandleSerialChanged (mon=<optimized out>, vm=0x3ff70074340, devAlias=<optimized out>, connected=<optimized out>, opaque=0x3ff70013f70) at ../../src/qemu/qemu_process.c:1480
 #4  0x000003ffd836a776 in qemuMonitorEmitSerialChange (mon=mon at entry=0x3ff500013f0, devAlias=devAlias at entry=0x1000b6940 "channel0", connected=<optimized out>) at ../../src/qemu/qemu_monitor.c:1558
 #5  0x000003ffd8378e52 in qemuMonitorJSONHandleSerialChange (mon=0x3ff500013f0, data=0x1000b79a0) at ../../src/qemu/qemu_monitor_json.c:1133
 #6  0x000003ffd8378930 in qemuMonitorJSONIOProcessEvent (mon=<optimized out>, mon at entry=0x3ff500013f0, obj=obj at entry=0x1000b6780) at ../../src/qemu/qemu_monitor_json.c:182
 #7  0x000003ffd837edee in qemuMonitorJSONIOProcessLine (mon=0x3ff500013f0, mon at entry=<error reading variable: value has been optimized out>, line=0x1000b8760 "{\"timestamp\": {\"seconds\": 1528444997, \"microseconds\": 125231}, \"event\": \"VSERPORT_CHANGE\", \"data\": {\"open\": false, \"id\": \"channel0\"}}", msg=0x3ff917f9850, msg at entry=<error reading variable: value has been optimized out>) at ../../src/qemu/qemu_monitor_json.c:211
 #8  0x000003ffd837ef86 in qemuMonitorJSONIOProcess (mon=<optimized out>, mon at entry=0x3ff500013f0, data=0x10008c4c0 "{\"return\": [{\"arch\": \"other\", \"current\": true, \"props\": {\"core-id\": 0}, \"CPU\": 0, \"qom_path\": \"/machine/unattached/device[0]\", \"halted\": false, \"thread_id\": 131501}, {\"arch\": \"other\", \"current\": false"..., len=477, msg=<optimized out>, msg at entry=0x3ff917f9850) at ../../src/qemu/qemu_monitor_json.c:253
 #9  0x000003ffd836757a in qemuMonitorIOProcess (mon=mon at entry=0x3ff500013f0) at ../../src/qemu/qemu_monitor.c:447
 #10 0x000003ffd836863e in qemuMonitorIO (watch=<error reading variable: value has been optimized out>, fd=<optimized out>, events=0, events at entry=<error reading variable: value has been optimized out>, opaque=0x3ff500013f0, opaque at entry=<error reading variable: value has been optimized out>) at ../../src/qemu/qemu_monitor.c:702
 #11 0x000003fffdb4033a in virEventPollDispatchHandles (nfds=<optimized out>, fds=0x1000b7160) at ../../src/util/vireventpoll.c:508
 #12 0x000003fffdb4055e in virEventPollRunOnce () at ../../src/util/vireventpoll.c:657
 #13 0x000003fffdb3e782 in virEventRunDefaultImpl () at ../../src/util/virevent.c:327
 #14 0x000003fffdc89400 in virNetDaemonRun (dmn=0x1000b2510) at ../../src/rpc/virnetdaemon.c:850
 #15 0x000000010002a816 in main (argc=<optimized out>, argv=<optimized out>) at ../../src/remote/remote_daemon.c:1460

Signed-off-by: Marc Hartmayer <mhartmay at linux.ibm.com>
Reviewed-by: Bjoern Walk <bwalk at linux.ibm.com>
Reviewed-by: Boris Fiuczynski <fiuczy at linux.ibm.com>
---
 src/qemu/qemu_driver.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 971cf3c2750a..28769878cc58 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -932,12 +932,15 @@ qemuStateInitialize(bool privileged,
                             qemuDomainManagedSaveLoad,
                             qemu_driver);
 
-    qemuProcessReconnectAll(qemu_driver);
-
+    /* must be initialized before trying to reconnect to all the
+     * running domains since there might occur some QEMU monitor
+     * events that will be dispatched to the worker pool */
     qemu_driver->workerPool = virThreadPoolNew(0, 1, 0, qemuProcessEventHandler, qemu_driver);
     if (!qemu_driver->workerPool)
         goto error;
 
+    qemuProcessReconnectAll(qemu_driver);
+
     virNWFilterRegisterCallbackDriver(&qemuCallbackDriver);
     return 0;
 
-- 
2.13.4