[PATCH v1] qemu_driver: Don't handle the EOF event if monitor changed

[tugy@xxxxxxxxxxxxxxx]

From: Guoyi Tu <tugy@xxxxxxxxxxxxxxx>

Currently, libvirt creates a thread pool with only on thread to handle all
qemu monitor events for virtual machines, In the cases that if the thread
gets stuck while handling a monitor EOF event, such as unable to kill the
virtual machine process or release resources, the events of other virtual
machine will be also blocked, which will lead to the abnormal behavior of
other virtual machines.

For instance, when another virtual machine completes a shutdown operation
and the monitor EOF event has been queued but remains unprocessed, we
immediately destroy and start the virtual machine again, at a later time
when EOF event get processed, the processMonitorEOFEvent() will kill the
virtual machine that just started.

To address this issue, in the processMonitorEOFEvent(), we check whether
the current virtual machine's monitor object matches the one at the time
the event was generated. If they do not match, we immediately return.

Signed-off-by: Guoyi Tu <tugy@xxxxxxxxxxxxxxx>
Signed-off-by: dengpengcheng <dengpc12@xxxxxxxxxxxxxxx>
---
 src/qemu/qemu_domain.c  |  2 +-
 src/qemu/qemu_driver.c  | 11 +++++++++--
 src/qemu/qemu_process.c |  2 +-
 3 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index 953808fcfe..435ee621df 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -11470,7 +11470,6 @@ qemuProcessEventFree(struct qemuProcessEvent *event)
     case QEMU_PROCESS_EVENT_NETDEV_STREAM_DISCONNECTED:
     case QEMU_PROCESS_EVENT_NIC_RX_FILTER_CHANGED:
     case QEMU_PROCESS_EVENT_SERIAL_CHANGED:
-    case QEMU_PROCESS_EVENT_MONITOR_EOF:
     case QEMU_PROCESS_EVENT_GUEST_CRASHLOADED:
         g_free(event->data);
         break;
@@ -11484,6 +11483,7 @@ qemuProcessEventFree(struct qemuProcessEvent *event)
     case QEMU_PROCESS_EVENT_UNATTENDED_MIGRATION:
     case QEMU_PROCESS_EVENT_RESET:
     case QEMU_PROCESS_EVENT_NBDKIT_EXITED:
+    case QEMU_PROCESS_EVENT_MONITOR_EOF:
     case QEMU_PROCESS_EVENT_LAST:
         break;
     }
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index d00d2a27c6..57acafb48b 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -3854,7 +3854,8 @@ processJobStatusChangeEvent(virDomainObj *vm,
 
 static void
 processMonitorEOFEvent(virQEMUDriver *driver,
-                       virDomainObj *vm)
+                       virDomainObj *vm,
+                       qemuMonitor *mon)
 {
     qemuDomainObjPrivate *priv = vm->privateData;
     int eventReason = VIR_DOMAIN_EVENT_STOPPED_SHUTDOWN;
@@ -3863,6 +3864,12 @@ processMonitorEOFEvent(virQEMUDriver *driver,
     unsigned int stopFlags = 0;
     virObjectEvent *event = NULL;
 
+    if (priv->mon != mon) {
+        VIR_DEBUG("Domain %p '%s' has been shutdown, ignoring EOF",
+                   vm, vm->def->name);
+        return;
+    }
+
     if (qemuProcessBeginStopJob(vm, VIR_JOB_DESTROY, true) < 0)
         return;
 
@@ -4082,7 +4089,7 @@ static void qemuProcessEventHandler(void *data, void *opaque)
         processJobStatusChangeEvent(vm, processEvent->data);
         break;
     case QEMU_PROCESS_EVENT_MONITOR_EOF:
-        processMonitorEOFEvent(driver, vm);
+        processMonitorEOFEvent(driver, vm, processEvent->data);
         break;
     case QEMU_PROCESS_EVENT_PR_DISCONNECT:
         processPRDisconnectEvent(vm);
diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
index f32e82bbd1..ff54e947fe 100644
--- a/src/qemu/qemu_process.c
+++ b/src/qemu/qemu_process.c
@@ -316,7 +316,7 @@ qemuProcessHandleMonitorEOF(qemuMonitor *mon,
     }
 
     qemuProcessEventSubmit(vm, QEMU_PROCESS_EVENT_MONITOR_EOF,
-                           0, 0, NULL);
+                           0, 0, priv->mon);
 
     /* We don't want this EOF handler to be called over and over while the
      * thread is waiting for a job.
-- 
2.17.1
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