On Fri, Jan 25, 2019 at 06:24:16PM +0100, Michal Hocko wrote: > On Fri 25-01-19 11:56:24, Johannes Weiner wrote: > > On Wed, Jan 09, 2019 at 11:03:06AM -0800, akpm@xxxxxxxxxxxxxxxxxxxx wrote: > > > > > > The patch titled > > > Subject: memcg: do not report racy no-eligible OOM tasks > > > has been added to the -mm tree. Its filename is > > > memcg-do-not-report-racy-no-eligible-oom-tasks.patch > > > > > > This patch should soon appear at > > > http://ozlabs.org/~akpm/mmots/broken-out/memcg-do-not-report-racy-no-eligible-oom-tasks.patch > > > and later at > > > http://ozlabs.org/~akpm/mmotm/broken-out/memcg-do-not-report-racy-no-eligible-oom-tasks.patch > > > > > > Before you just go and hit "reply", please: > > > a) Consider who else should be cc'ed > > > b) Prefer to cc a suitable mailing list as well > > > c) Ideally: find the original patch on the mailing list and do a > > > reply-to-all to that, adding suitable additional cc's > > > > > > *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** > > > > > > The -mm tree is included into linux-next and is updated > > > there every 3-4 working days > > > > > > ------------------------------------------------------ > > > From: Michal Hocko <mhocko@xxxxxxxx> > > > Subject: memcg: do not report racy no-eligible OOM tasks > > > > > > Tetsuo has reported [1] that a single process group memcg might easily > > > swamp the log with no-eligible oom victim reports due to race between the > > > memcg charge and oom_reaper > > > > > > Thread 1 Thread2 oom_reaper > > > try_charge try_charge > > > mem_cgroup_out_of_memory > > > mutex_lock(oom_lock) > > > mem_cgroup_out_of_memory > > > mutex_lock(oom_lock) > > > out_of_memory > > > select_bad_process > > > oom_kill_process(current) > > > wake_oom_reaper > > > oom_reap_task > > > MMF_OOM_SKIP->victim > > > mutex_unlock(oom_lock) > > > out_of_memory > > > select_bad_process # no task > > > > > > If Thread1 didn't race it would bail out from try_charge and force the > > > charge. We can achieve the same by checking tsk_is_oom_victim inside the > > > oom_lock and therefore close the race. > > > > > > [1] http://lkml.kernel.org/r/bb2074c0-34fe-8c2c-1c7d-db71338f1e7f@xxxxxxxxxxxxxxxxxxx > > > Link: http://lkml.kernel.org/r/20190107143802.16847-3-mhocko@xxxxxxxxxx > > > Signed-off-by: Michal Hocko <mhocko@xxxxxxxx> > > > Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> > > > Cc: Johannes Weiner <hannes@xxxxxxxxxxx> > > > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > > > > It looks like this problem is happening in production systems: > > > > https://www.spinics.net/lists/cgroups/msg21268.html > > > > where the threads don't exit because they are trapped writing out the > > oom messages to a slow console (running the reproducer from this email > > thread triggers the oom flooding). > > > > So IMO we should put this into 5.0 and add: > > Please note that Tetsuo has found out that this will not work with the > CLONE_VM without CLONE_SIGHAND cases and his http://lkml.kernel.org/r/01370f70-e1f6-ebe4-b95e-0df21a0bc15e@xxxxxxxxxxxxxxxxxxx > should handle this case as well. I've only had objections to the > changelog but other than that the patch looked sensible to me. I see. Yeah that looks reasonable to me too. Tetsuo, could you include the Fixes: and CC: stable in your patch?
