On Thu, Jul 21, 2016 at 02:43:34PM +0200, Vegard Nossum wrote: > The rules for net_mutex are very simple, it's used in very few places so > I don't see how the locking could get messed up there. I'll buy your > theory that the lock is held for a long time if there are a lot of > namespaces to iterate over. I decided to time it myself and it seems > that cleanup_net() can hold the mutex for 30-40 seconds at a time, which > is surely wrong. > so on a hunch I disabled DEBUG_KOBJECT_RELEASE, and that does indeed > solve the problem -- cleanup_net() still holds the mutex for fairly > long, but only up to max ~5 seconds at a time as opposed to 30-40. Yeah, I never ran with that option enabled (it used to cause my testbox to not boot, and I never got around to debugging why). I thought five seconds was painful enough. I guess we have different thresholds for acceptable behaviour here :-) Could be one of the other debug options I had enabled exacerbates the cleanup_net problem in a similar way though. > There's maybe a case for cleanup_net() to release the mutex every now > and again during cleanup, but I was also seeing a few other hung tasks > unrelated to net_mutex when I disabled the unshare() system call in > trinity, which makes me wonder if we need a more general solution. Not sure. We may have to just look at these on a case by case basis. Dave -- To unsubscribe from this list: send the line "unsubscribe trinity" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
