From: David Rientjes <rientjes@google.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
akpm@linux-foundation.org, aarcange@redhat.com,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: Multiple oom_reaper BUGs: unmap_page_range racing with exit_mmap
Date: Thu, 7 Dec 2017 13:55:07 -0800 (PST) [thread overview]
Message-ID: <alpine.DEB.2.10.1712071352480.135101@chino.kir.corp.google.com> (raw)
In-Reply-To: <20171207163003.GM20234@dhcp22.suse.cz>
On Thu, 7 Dec 2017, Michal Hocko wrote:
> yes. I will fold the following in if this turned out to really address
> David's issue. But I suspect this will be the case considering the NULL
> pmd in the report which would suggest racing with free_pgtable...
>
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
next prev parent reply other threads:[~2017-12-07 21:55 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-06 2:43 Multiple oom_reaper BUGs: unmap_page_range racing with exit_mmap David Rientjes
2017-12-06 2:58 ` David Rientjes
[not found] ` <201712060328.vB63SrDK069830@www262.sakura.ne.jp>
2017-12-06 7:48 ` David Rientjes
2017-12-06 9:00 ` Michal Hocko
[not found] ` <201712070720.vB77KlBQ009754@www262.sakura.ne.jp>
2017-12-07 8:28 ` Michal Hocko
2017-12-07 8:44 ` Michal Hocko
2017-12-07 11:00 ` Tetsuo Handa
2017-12-07 21:22 ` David Rientjes
2017-12-08 7:50 ` Michal Hocko
2017-12-06 11:37 ` Tetsuo Handa
2017-12-06 8:50 ` Michal Hocko
2017-12-06 8:31 ` Michal Hocko
2017-12-07 11:35 ` Michal Hocko
2017-12-07 15:44 ` Tetsuo Handa
2017-12-07 16:30 ` Michal Hocko
2017-12-07 21:55 ` David Rientjes [this message]
2017-12-08 9:26 ` David Rientjes
2017-12-08 11:27 ` Michal Hocko
2017-12-08 10:11 ` Tetsuo Handa
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