On Mon, May 26, 2014 at 11:17:42AM -0700, Linus Torvalds wrote: > On Mon, May 26, 2014 at 8:27 AM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: > > > > That's the livelock. OK. > > Hmm. Is there any reason we don't have some exclusion around > "check_submounts_and_drop()"? > > That would seem to be the simplest way to avoid any livelock: just > don't allow concurrent calls (we could make the lock per-filesystem or > whatever). This whole case should all be for just exceptional cases > anyway. > > We already sleep in that thing (well, "cond_resched()"), so taking a > mutex should be fine. What makes you think that it's another check_submounts_and_drop()? And not, e.g., shrink_dcache_parent(). Or memory shrinkers. Or some twit sitting in a subdirectory and doing stat(2) in a loop, for that matter... I really, really wonder WTF is causing that - we have spent 20-odd seconds spinning while dentries in there were being evicted by something. That - on sysfs, where dentry_kill() should be non-blocking and very fast. Something very fishy is going on and I'd really like to understand the use pattern we are seeing there. -- 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
