On Fri 08-12-17 01:26:46, David Rientjes wrote: > On Thu, 7 Dec 2017, David Rientjes wrote: > > > I'm backporting and testing the following patch against Linus's tree. To > > clarify an earlier point, we don't actually have any change from upstream > > code that allows for free_pgtables() before the > > set_bit(MMF_OOM_SKIP);down_write();up_write() cycle. > > > > diff --git a/include/linux/oom.h b/include/linux/oom.h > > --- a/include/linux/oom.h > > +++ b/include/linux/oom.h > > @@ -66,6 +66,15 @@ static inline bool tsk_is_oom_victim(struct task_struct * tsk) > > return tsk->signal->oom_mm; > > } > > > > +/* > > + * Use this helper if tsk->mm != mm and the victim mm needs a special > > + * handling. This is guaranteed to stay true after once set. > > + */ > > +static inline bool mm_is_oom_victim(struct mm_struct *mm) > > +{ > > + return test_bit(MMF_OOM_VICTIM, &mm->flags); > > +} > > + > > /* > > * Checks whether a page fault on the given mm is still reliable. > > * This is no longer true if the oom reaper started to reap the > > diff --git a/include/linux/sched/coredump.h b/include/linux/sched/coredump.h > > --- a/include/linux/sched/coredump.h > > +++ b/include/linux/sched/coredump.h > > @@ -71,6 +71,7 @@ static inline int get_dumpable(struct mm_struct *mm) > > #define MMF_HUGE_ZERO_PAGE 23 /* mm has ever used the global huge zero page */ > > #define MMF_DISABLE_THP 24 /* disable THP for all VMAs */ > > #define MMF_DISABLE_THP_MASK (1 << MMF_DISABLE_THP) > > +#define MMF_OOM_VICTIM 25 /* mm is the oom victim */ > > > > #define MMF_INIT_MASK (MMF_DUMPABLE_MASK | MMF_DUMP_FILTER_MASK |\ > > MMF_DISABLE_THP_MASK) > > diff --git a/mm/mmap.c b/mm/mmap.c > > --- a/mm/mmap.c > > +++ b/mm/mmap.c > > @@ -3019,20 +3019,20 @@ void exit_mmap(struct mm_struct *mm) > > /* Use -1 here to ensure all VMAs in the mm are unmapped */ > > unmap_vmas(&tlb, vma, 0, -1); > > > > - set_bit(MMF_OOM_SKIP, &mm->flags); > > - if (unlikely(tsk_is_oom_victim(current))) { > > + if (unlikely(mm_is_oom_victim(mm))) { > > /* > > * Wait for oom_reap_task() to stop working on this > > * mm. Because MMF_OOM_SKIP is already set before > > * calling down_read(), oom_reap_task() will not run > > * on this "mm" post up_write(). > > * > > - * tsk_is_oom_victim() cannot be set from under us > > + * mm_is_oom_victim() cannot be set from under us > > * either because current->mm is already set to NULL > > * under task_lock before calling mmput and oom_mm is > > * set not NULL by the OOM killer only if current->mm > > * is found not NULL while holding the task_lock. > > */ > > + set_bit(MMF_OOM_SKIP, &mm->flags); > > down_write(&mm->mmap_sem); > > up_write(&mm->mmap_sem); > > } > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > > --- a/mm/oom_kill.c > > +++ b/mm/oom_kill.c > > @@ -683,8 +683,10 @@ static void mark_oom_victim(struct task_struct *tsk) > > return; > > > > /* oom_mm is bound to the signal struct life time. */ > > - if (!cmpxchg(&tsk->signal->oom_mm, NULL, mm)) > > + if (!cmpxchg(&tsk->signal->oom_mm, NULL, mm)) { > > mmgrab(tsk->signal->oom_mm); > > + set_bit(MMF_OOM_VICTIM, &mm->flags); > > + } > > > > /* > > * Make sure that the task is woken up from uninterruptible sleep > > > > This passes all functional testing that I have and I can create a > synthetic testcase that can trigger at least MMF_OOM_VICTIM getting set > while oom_reaper is still working on an mm that this prevents, so feel > free to add an > > Acked-by: David Rientjes <rientjes@xxxxxxxxxx> > > with a variant of your previous changelogs. Thanks! > > I think it would appropriate to cc stable for 4.14 and add a > > Fixes: 212925802454 ("mm: oom: let oom_reap_task and exit_mmap run > concurrently") > > if nobody disagrees, which I think you may have already done on a previous > iteration. Thanks for your testing! I will repost the patch later today. > We can still discuss if there are any VM_LOCKED subtleties in the this > thread, but I have no evidence that it is responsible for any issues. Yes this is worth a separate discussion. -- 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>