oom: introduce find_lock_task_mm() to fix !mm false positives
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From: KAMEZAWA Hiroyuki on 31 May 2010 21:10 On Mon, 31 May 2010 18:36:34 +0900 (JST) KOSAKI Motohiro <kosaki.motohiro(a)jp.fujitsu.com> wrote: > From: Oleg Nesterov <oleg(a)redhat.com> > Subject: [PATCH 3/5] oom: introduce find_lock_task_mm() to fix !mm false positives > > Almost all ->mm == NUL checks in oom_kill.c are wrong. > > The current code assumes that the task without ->mm has already > released its memory and ignores the process. However this is not > necessarily true when this process is multithreaded, other live > sub-threads can use this ->mm. > > - Remove the "if (!p->mm)" check in select_bad_process(), it is > just wrong. > > - Add the new helper, find_lock_task_mm(), which finds the live > thread which uses the memory and takes task_lock() to pin ->mm > > - change oom_badness() to use this helper instead of just checking > ->mm != NULL. > > - As David pointed out, select_bad_process() must never choose the > task without ->mm, but no matter what badness() returns the > task can be chosen if nothing else has been found yet. > > Note! This patch is not enough, we need more changes. > > - badness() was fixed, but oom_kill_task() still ignores > the task without ->mm > > This will be addressed later. > > Signed-off-by: Oleg Nesterov <oleg(a)redhat.com> > Cc: David Rientjes <rientjes(a)google.com> > Signed-off-by: KOSAKI Motohiro <kosaki.motohiro(a)jp.fujitsu.com> [rebase > latest -mm and remove some obsoleted description] Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu(a)jp.fujitsu.com> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: David Rientjes on 1 Jun 2010 16:50 On Mon, 31 May 2010, KOSAKI Motohiro wrote: > From: Oleg Nesterov <oleg(a)redhat.com> > Subject: [PATCH 3/5] oom: introduce find_lock_task_mm() to fix !mm false positives > > Almost all ->mm == NUL checks in oom_kill.c are wrong. > > The current code assumes that the task without ->mm has already > released its memory and ignores the process. However this is not > necessarily true when this process is multithreaded, other live > sub-threads can use this ->mm. > > - Remove the "if (!p->mm)" check in select_bad_process(), it is > just wrong. > > - Add the new helper, find_lock_task_mm(), which finds the live > thread which uses the memory and takes task_lock() to pin ->mm > > - change oom_badness() to use this helper instead of just checking > ->mm != NULL. > > - As David pointed out, select_bad_process() must never choose the > task without ->mm, but no matter what badness() returns the > task can be chosen if nothing else has been found yet. > > Note! This patch is not enough, we need more changes. > > - badness() was fixed, but oom_kill_task() still ignores > the task without ->mm > > This will be addressed later. > > Signed-off-by: Oleg Nesterov <oleg(a)redhat.com> > Cc: David Rientjes <rientjes(a)google.com> > Signed-off-by: KOSAKI Motohiro <kosaki.motohiro(a)jp.fujitsu.com> [rebase > latest -mm and remove some obsoleted description] This is already pushed as part of my oom killer rewrite in patch 15/18 "oom: introduce find_lock_task_mm to fix !mm false positives". -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: KOSAKI Motohiro on 3 Jun 2010 03:00
> > Signed-off-by: Oleg Nesterov <oleg(a)redhat.com> > > Cc: David Rientjes <rientjes(a)google.com> > > Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu(a)jp.fujitsu.com> > > Signed-off-by: KOSAKI Motohiro <kosaki.motohiro(a)jp.fujitsu.com> > > Could you see my previous comment? > http://lkml.org/lkml/2010/6/2/325 > Anyway, I added my review sign > > Reviewed-by: Minchan Kim <minchan.kim(a)gmail.com> Sorry, I had lost your comment ;) But personally I don't like find_alive_subthread() because such function actually does, 1) iterate threads in the same thread group 2) find alive (a.k.a have ->mm) thread 3) lock the task and, I think (3) is most important role of this function. So, I prefer to contain "lock" word. Otherwise, people easily forget to cann task_unlock(). But I'm ok to rename any give me better name. Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |