On Wed, May 28, 2014 at 04:11:36PM +0300, Mika Westerberg wrote: > I added this on top of your previus patch and unfortunately the livelock > is still there :-( > > >From the previous log, it looks like udev is doing exactly same operation > (check_submounts_and_drop) on 4 of the CPUs in paraller: 4 threads trying to resolve some pathnames in that subtree for some reason. All of them hitting ->d_revalidate() on the spot - basically, the first invalidated directory... OK, it's not ->i_lock, it's ->d_lock on parent being grabbed after that on child, while d_walk() keeps taking them in opposite order. Hmm... In principle we could do the following: * split dentry_kill() into the part that is taking locks and the rest of it. * in case of trylock failure have shrink_dentry_list() do read_seqlock_excl(&rename_lock) (which will stabilize ->d_parent) and take ->d_lock in the right order, drop rename_lock and call __dentry_kill(). AFAICS, that would kill the livelock for good. We still have ->i_lock trylock failures to deal with, but those are less of a problem - d_walk() won't step on ->i_lock at all. I'm going to grab a couple of hours of sleep and try to put together something along those lines... -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
