On Wed, Jul 04, 2018 at 13:09:01 +0200, Michal Privoznik wrote:

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@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;

I think the following alignment would be a bit better: return !priv->job.asyncJob || job == QEMU_JOB_NONE || (priv->job.mask & JOB_MASK(job)) != 0; And I would probably put the job == QEMU_JOB_NONE check first, but it doesn't make any functional difference. Reviewed-by: Jiri Denemark <jdenemar@redhat.com>