[libvirt] [PATCH 08/11] Fix monitor usage in qemuDomainHotplugVcpus

[Ján Tomko]

Exit the monitor right after we've done with it to get
the virDomainObjPtr lock back, otherwise we might be accessing
vm->def while it's being cleaned up by qemuProcessStop.

If the domain crashed while we were in the monitor, exit
early instead of changing vm->def which is now the persistent
definition.
---
 src/qemu/qemu_driver.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 07b061e..20b54cc 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -4443,7 +4443,7 @@ static int qemuDomainHotplugVcpus(virQEMUDriverPtr driver,
             if (rc == 0)
                 goto unsupported;
             if (rc < 0)
-                goto cleanup;
+                goto exit_monitor;
 
             vcpus++;
         }
@@ -4454,7 +4454,7 @@ static int qemuDomainHotplugVcpus(virQEMUDriverPtr driver,
             if (rc == 0)
                 goto unsupported;
             if (rc < 0)
-                goto cleanup;
+                goto exit_monitor;
 
             vcpus--;
         }
@@ -4471,6 +4471,10 @@ static int qemuDomainHotplugVcpus(virQEMUDriverPtr driver,
      * fatal */
     if ((ncpupids = qemuMonitorGetCPUInfo(priv->mon, &cpupids)) <= 0) {
         virResetLastError();
+        goto exit_monitor;
+    }
+    if (qemuDomainObjExitMonitorAlive(driver, vm) < 0) {
+        ret = -1;
         goto cleanup;
     }
 
@@ -4591,10 +4595,10 @@ static int qemuDomainHotplugVcpus(virQEMUDriverPtr driver,
     cpupids = NULL;
 
  cleanup:
-    qemuDomainObjExitMonitor(driver, vm);
-    vm->def->vcpus = vcpus;
     VIR_FREE(cpupids);
     VIR_FREE(mem_mask);
+    if (virDomainObjIsActive(vm))
+        vm->def->vcpus = vcpus;
     virDomainAuditVcpu(vm, oldvcpus, nvcpus, "update", rc == 1);
     if (cgroup_vcpu)
         virCgroupFree(&cgroup_vcpu);
@@ -4603,6 +4607,8 @@ static int qemuDomainHotplugVcpus(virQEMUDriverPtr driver,
  unsupported:
     virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
                    _("cannot change vcpu count of this domain"));
+ exit_monitor:
+    qemuDomainObjExitMonitor(driver, vm);
     goto cleanup;
 }
 
-- 
2.0.4