On Wed 12-06-13 13:49:47, David Rientjes wrote: > On Wed, 12 Jun 2013, Michal Hocko wrote: > > > The patch is a big improvement with a minimum code overhead. Blocking > > any task which sits on top of an unpredictable amount of locks is just > > broken. So regardless how many users are affected we should merge it and > > backport to stable trees. The problem is there since ever. We seem to > > be surprisingly lucky to not hit this more often. > > > > Right now it appears that that number of users is 0 and we're talking > about a problem that was reported in 3.2 that was released a year and a > half ago. The rules of inclusion in stable also prohibit such a change > from being backported, specifically "It must fix a real bug that bothers > people (not a, "This could be a problem..." type thing)". As you can see there is an user seeing this in 3.2. The bug is _real_ and I do not see what you are objecting against. Do you really think that sitting on a time bomb is preferred more? > We have deployed memcg on a very large number of machines and I can run a > query over all software watchdog timeouts that have occurred by > deadlocking on i_mutex during memcg oom. It returns 0 results. Do you capture /prc/<pid>/stack for each of them to find that your deadlock (and you have reported that they happen) was in fact caused by a locking issue? These kind of deadlocks might got unnoticed especially when the oom is handled by userspace by increasing the limit (my mmecg is stuck and increasing the limit a bit always helped). > > I am not quite sure I understand your reservation about the patch to be > > honest. Andrew still hasn't merged this one although 1/2 is in. > > Perhaps he is as unconvinced? The patch adds 100 lines of code, including > fields to task_struct for memcg, for a problem that nobody can reproduce. > My question still stands: can anybody, even with an instrumented kernel to > make it more probable, reproduce the issue this is addressing? So the referenced discussion is not sufficient? -- 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>