Daniel P. Berrange wrote:
On Thu, Jun 21, 2012 at 09:56:54AM -0600, Jim Fehlig wrote:
From 583be33213e922899b23f036494886397b2549dc Mon Sep 17 00:00:00 2001 From: Jim Fehlig <jfehlig@suse.com> Date: Thu, 21 Jun 2012 09:21:44 -0600 Subject: [PATCH] Fix deadlock on libvirtd shutdown
When shutting down libvirtd, the virNetServer shutdown can deadlock if there are in-flight jobs being handled by virNetServerHandleJob(). virNetServerFree() will acquire the virNetServer lock and call virThreadPoolFree() to terminate the workers, waiting for the workers to finish. But in-flight workers will attempt to acquire the virNetServer lock, resulting in deadlock.
Fix the deadlock by unlocking the virNetServer lock before calling virThreadPoolFree(). This is safe since the virNetServerPtr object is ref-counted and only decrementing the ref count needs to be protected. Additionally, there is no need to re-acquire the lock after virThreadPoolFree() completes as all the workers have terminated. --- src/rpc/virnetserver.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/src/rpc/virnetserver.c b/src/rpc/virnetserver.c index ae19e84..9d71e53 100644 --- a/src/rpc/virnetserver.c +++ b/src/rpc/virnetserver.c @@ -766,10 +766,9 @@ void virNetServerFree(virNetServerPtr srv) virNetServerLock(srv); VIR_DEBUG("srv=%p refs=%d", srv, srv->refs); srv->refs--; - if (srv->refs > 0) { - virNetServerUnlock(srv); + virNetServerUnlock(srv); + if (srv->refs > 0) return; - }
for (i = 0 ; i < srv->nservices ; i++) virNetServerServiceToggle(srv->services[i], false); @@ -805,7 +804,6 @@ void virNetServerFree(virNetServerPtr srv) virNetServerMDNSFree(srv->mdns); #endif
- virNetServerUnlock(srv); virMutexDestroy(&srv->lock); VIR_FREE(srv); }
ACK,
We really should resurrect the patches adding virAtomic for refcounting :-)
Thanks for the help with this. I've pushed it now. Regards, Jim