[libvirt] [PATCH] qemuDomainNestedJobAllowed: Allow QEMU_JOB_NONE

[Michal Privoznik]

https://bugzilla.redhat.com/show_bug.cgi?id=1598084

When creating a snapshot with --quiesce an async job is grabbed
and just before executing guest fs-freeze command an agent job is
grabbed. This is achieved by calling

  qemuDomainObjBeginJobInternal(job = QEMU_JOB_NONE,
                                agentJob = QEMU_AGENT_JOB_MODIFY);

Since there already is an async job set on the domain (by the
same thread) qemuDomainNestedJobAllowed(priv, job) is consulted
if @job is allowed by job mask. But this function returns false
(meaning sync @job is not allowed) which leads to a deadlock.

Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
---
 src/qemu/qemu_domain.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index a60bca29ca..1b8fb71ba8 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -6414,7 +6414,9 @@ qemuDomainObjReleaseAsyncJob(virDomainObjPtr obj)
 static bool
 qemuDomainNestedJobAllowed(qemuDomainObjPrivatePtr priv, qemuDomainJob job)
 {
-    return !priv->job.asyncJob || (priv->job.mask & JOB_MASK(job)) != 0;
+    return !priv->job.asyncJob ||
+        job == QEMU_JOB_NONE ||
+        (priv->job.mask & JOB_MASK(job)) != 0;
 }
 
 bool
-- 
2.16.4