Change in vdsm[master]: vm: fix _dom access when QEMU is dying

fromani at redhat.com fromani at redhat.com
Tue Apr 8 11:03:12 UTC 2014


Francesco Romani has uploaded a new change for review.

Change subject: vm: fix _dom access when QEMU is dying
......................................................................

vm: fix _dom access when QEMU is dying

commit 8fedf8bde3c28edb07add23c3e9b72681cb48e49 introduced a tiny
window for races between libvirt notifications (vm._onQemuDeath)
and polling for stats from engine.

This is demonstrated by bz1073478, but it really boils down
to how events are serialized.
In this case, a stats request from engine is being answered
while QEMU is being reported down and the _dom handle is being
shut down, we end up with an uncaught exception.

This patch address the reported race between polling and qemu death.
The window of vulnerability is (supposed to be) tiny
and the issue itself is hard to reproduce.

Sampling thread is theorically vulnerable to the a race of the
same type, but this problem will be addressed in a separate
patch.

Change-Id: Ibac9e75a484b228c67d5432b71e965bdf317b89c
Bug-Url: https://bugzilla.redhat.com/1073478
Signed-off-by: Francesco Romani <fromani at redhat.com>
---
M vdsm/virt/vm.py
1 file changed, 1 insertion(+), 1 deletion(-)


  git pull ssh://gerrit.ovirt.org:29418/vdsm refs/changes/39/26539/1

diff --git a/vdsm/virt/vm.py b/vdsm/virt/vm.py
index 0e19235..3d86598 100644
--- a/vdsm/virt/vm.py
+++ b/vdsm/virt/vm.py
@@ -4322,7 +4322,7 @@
                 max_mem = int(self.conf.get('memSize')) * 1024
                 min_mem = int(self.conf.get('memGuaranteedSize', '0')) * 1024
                 target_mem = dev.get('target', max_mem)
-                cur_mem = self._dom.info()[2]
+                cur_mem = self._dom.info()[2] if self._dom else 0
                 return {'balloon_max': str(max_mem),
                         'balloon_cur': str(cur_mem),
                         'balloon_min': str(min_mem),


-- 
To view, visit http://gerrit.ovirt.org/26539
To unsubscribe, visit http://gerrit.ovirt.org/settings

Gerrit-MessageType: newchange
Gerrit-Change-Id: Ibac9e75a484b228c67d5432b71e965bdf317b89c
Gerrit-PatchSet: 1
Gerrit-Project: vdsm
Gerrit-Branch: master
Gerrit-Owner: Francesco Romani <fromani at redhat.com>


More information about the vdsm-patches mailing list