On Sat, Apr 09, 2016 at 07:14:30PM +0300, Maxim Nestratov wrote: > Below is backtraces of two deadlocked threads: > > thread #1: > virDomainConfVMNWFilterTeardown > virNWFilterTeardownFilter > lock updateMutex <------------ > _virNWFilterTeardownFilter > try to lock interface <---------- > > thread #2: > learnIPAddressThread > lock interface <------- > virNWFilterInstantiateFilterLate > try to lock updateMutex <---------- > > The problem is fixed by unlocking interface before calling > virNWFilterInstantiateFilterLate to avoid updateMutex and interface ordering > deadlocks. Otherwise we are going to instantiate the filter while holding > interface lock, which will try to lock updateMutex, and if some other thread > instantiating a filter in parallel is holding updateMutex and is trying to > lock interface, both will deadlock. > Also it is safe to unlock interface before virNWFilterInstantiateFilterLate > because learnIPAddressThread stopped capturing packets and applied necessary > rules on the interface, while instantiating a new filter doesn't require a > locked interface. > > Signed-off-by: Maxim Nestratov <mnestratov@xxxxxxxxxxxxx> > --- The nwfilter code is complex. This seems to be fixing a small corner case because virDomainConfVMNWFilterTeardown should terminate that learnIPAddressThread, but it doesn't wait until that thread is terminated. I'm not sure, whether it's safe to unlock the iface. Do you have some reproducer for this deadlock? Pavel -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list