On Tue 09-07-13 15:08:08, Michal Hocko wrote: > On Tue 09-07-13 15:00:17, Michal Hocko wrote: > > On Mon 24-06-13 16:13:45, Johannes Weiner wrote: > > > Hi guys, > > > > > > On Sat, Jun 22, 2013 at 10:09:58PM +0200, azurIt wrote: > > > > >> But i'm sure of one thing - when problem occurs, nothing is able to > > > > >> access hard drives (every process which tries it is freezed until > > > > >> problem is resolved or server is rebooted). > > > > > > > > > >I would be really interesting to see what those tasks are blocked on. > > > > > > > > I'm trying to get it, stay tuned :) > > > > > > > > Today i noticed one bug, not 100% sure it is related to 'your' patch > > > > but i didn't seen this before. I noticed that i have lots of cgroups > > > > which cannot be removed - if i do 'rmdir <cgroup_directory>', it > > > > just hangs and never complete. Even more, it's not possible to > > > > access the whole cgroup filesystem until i kill that rmdir > > > > (anything, which tries it, just hangs). All unremoveable cgroups has > > > > this in 'memory.oom_control': oom_kill_disable 0 under_oom 1 > > > > > > Somebody acquires the OOM wait reference to the memcg and marks it > > > under oom but then does not call into mem_cgroup_oom_synchronize() to > > > clean up. That's why under_oom is set and the rmdir waits for > > > outstanding references. > > > > > > > And, yes, 'tasks' file is empty. > > > > > > It's not a kernel thread that does it because all kernel-context > > > handle_mm_fault() are annotated properly, which means the task must be > > > userspace and, since tasks is empty, have exited before synchronizing. > > > > Yes, well spotted. I have missed that while reviewing your patch. > > The follow up fix looks correct. > > Hmm, I guess you wanted to remove !(fault & VM_FAULT_ERROR) test as well > otherwise the else BUG() path would be unreachable and we wouldn't know > that something fishy is going on. No, scratch it! We need it for VM_FAULT_RETRY. Sorry about the noise. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>