From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> To: "Arkadiusz Miśkiewicz" <a.miskiewicz@gmail.com>, "Andrew Morton" <akpm@linux-foundation.org> Cc: Tejun Heo <tj@kernel.org>, cgroups@vger.kernel.org, Aleksa Sarai <asarai@suse.de>, Jay Kamat <jgkamat@fb.com>, Roman Gushchin <guro@fb.com>, Michal Hocko <mhocko@suse.com>, Johannes Weiner <hannes@cmpxchg.org>, linux-kernel@vger.kernel.org, Linus Torvalds <torvalds@linux-foundation.org>, linux-mm <linux-mm@kvack.org> Subject: [PATCH v2] oom, oom_reaper: do not enqueue same task twice Date: Sat, 26 Jan 2019 22:10:52 +0900 [thread overview] Message-ID: <1d161137-55a5-126f-b47e-b2625bd798ca@i-love.sakura.ne.jp> (raw) In-Reply-To: <2b0c7d6c-c58a-da7d-6f0a-4900694ec2d3@gmail.com> On 2019/01/26 20:29, Arkadiusz Miśkiewicz wrote: > On 26/01/2019 12:09, Tetsuo Handa wrote: >> Arkadiusz, will you try this patch? > > > Works. Several tries and always getting 0 pids.current after ~1s. > Thank you for testing. I updated this patch to use tsk->signal->oom_mm (a snapshot of tsk->mm saved by mark_oom_victim(tsk)) rather than raw tsk->mm so that we don't need to worry about possibility of changing tsk->mm across multiple wake_oom_reaper(tsk) calls. >From 9c9e935fc038342c48461aabca666f1b544e32b1 Mon Sep 17 00:00:00 2001 From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Date: Sat, 26 Jan 2019 21:57:25 +0900 Subject: [PATCH v2] oom, oom_reaper: do not enqueue same task twice Arkadiusz reported that enabling memcg's group oom killing causes strange memcg statistics where there is no task in a memcg despite the number of tasks in that memcg is not 0. It turned out that there is a bug in wake_oom_reaper() which allows enqueuing same task twice which makes impossible to decrease the number of tasks in that memcg due to a refcount leak. This bug existed since the OOM reaper became invokable from task_will_free_mem(current) path in out_of_memory() in Linux 4.7, but memcg's group oom killing made it easier to trigger this bug by calling wake_oom_reaper() on the same task from one out_of_memory() request. Fix this bug using an approach used by commit 855b018325737f76 ("oom, oom_reaper: disable oom_reaper for oom_kill_allocating_task"). As a side effect of this patch, this patch also avoids enqueuing multiple threads sharing memory via task_will_free_mem(current) path. Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Reported-by: Arkadiusz Miśkiewicz <arekm@maven.pl> Tested-by: Arkadiusz Miśkiewicz <arekm@maven.pl> Fixes: af8e15cc85a25315 ("oom, oom_reaper: do not enqueue task if it is on the oom_reaper_list head") --- mm/oom_kill.c | 17 +++++++---------- 1 file changed, 7 insertions(+), 10 deletions(-) diff --git a/mm/oom_kill.c b/mm/oom_kill.c index f0e8cd9..057bfee 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -505,14 +505,6 @@ bool __oom_reap_task_mm(struct mm_struct *mm) struct vm_area_struct *vma; bool ret = true; - /* - * Tell all users of get_user/copy_from_user etc... that the content - * is no longer stable. No barriers really needed because unmapping - * should imply barriers already and the reader would hit a page fault - * if it stumbled over a reaped memory. - */ - set_bit(MMF_UNSTABLE, &mm->flags); - for (vma = mm->mmap ; vma; vma = vma->vm_next) { if (!can_madv_dontneed_vma(vma)) continue; @@ -647,8 +639,13 @@ static int oom_reaper(void *unused) static void wake_oom_reaper(struct task_struct *tsk) { - /* tsk is already queued? */ - if (tsk == oom_reaper_list || tsk->oom_reaper_list) + /* + * Tell all users of get_user/copy_from_user etc... that the content + * is no longer stable. No barriers really needed because unmapping + * should imply barriers already and the reader would hit a page fault + * if it stumbled over a reaped memory. + */ + if (test_and_set_bit(MMF_UNSTABLE, &tsk->signal->oom_mm->flags)) return; get_task_struct(tsk); -- 1.8.3.1
WARNING: multiple messages have this Message-ID (diff)
From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> To: "Arkadiusz Miśkiewicz" <a.miskiewicz@gmail.com>, "Andrew Morton" <akpm@linux-foundation.org> Cc: Tejun Heo <tj@kernel.org>, cgroups@vger.kernel.org, Aleksa Sarai <asarai@suse.de>, Jay Kamat <jgkamat@fb.com>, Roman Gushchin <guro@fb.com>, Michal Hocko <mhocko@suse.com>, Johannes Weiner <hannes@cmpxchg.org>, linux-kernel@vger.kernel.org, Linus Torvalds <torvalds@linux-foundation.org>, linux-mm <linux-mm@kvack.org> Subject: [PATCH v2] oom, oom_reaper: do not enqueue same task twice Date: Sat, 26 Jan 2019 22:10:52 +0900 [thread overview] Message-ID: <1d161137-55a5-126f-b47e-b2625bd798ca@i-love.sakura.ne.jp> (raw) Message-ID: <20190126131052.6gJrKtIQoKnpiLufUmpzm8Mg5-_tM9syO8M-QEw0g7Q@z> (raw) In-Reply-To: <2b0c7d6c-c58a-da7d-6f0a-4900694ec2d3@gmail.com> On 2019/01/26 20:29, Arkadiusz Miśkiewicz wrote: > On 26/01/2019 12:09, Tetsuo Handa wrote: >> Arkadiusz, will you try this patch? > > > Works. Several tries and always getting 0 pids.current after ~1s. > Thank you for testing. I updated this patch to use tsk->signal->oom_mm (a snapshot of tsk->mm saved by mark_oom_victim(tsk)) rather than raw tsk->mm so that we don't need to worry about possibility of changing tsk->mm across multiple wake_oom_reaper(tsk) calls. From 9c9e935fc038342c48461aabca666f1b544e32b1 Mon Sep 17 00:00:00 2001 From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Date: Sat, 26 Jan 2019 21:57:25 +0900 Subject: [PATCH v2] oom, oom_reaper: do not enqueue same task twice Arkadiusz reported that enabling memcg's group oom killing causes strange memcg statistics where there is no task in a memcg despite the number of tasks in that memcg is not 0. It turned out that there is a bug in wake_oom_reaper() which allows enqueuing same task twice which makes impossible to decrease the number of tasks in that memcg due to a refcount leak. This bug existed since the OOM reaper became invokable from task_will_free_mem(current) path in out_of_memory() in Linux 4.7, but memcg's group oom killing made it easier to trigger this bug by calling wake_oom_reaper() on the same task from one out_of_memory() request. Fix this bug using an approach used by commit 855b018325737f76 ("oom, oom_reaper: disable oom_reaper for oom_kill_allocating_task"). As a side effect of this patch, this patch also avoids enqueuing multiple threads sharing memory via task_will_free_mem(current) path. Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Reported-by: Arkadiusz Miśkiewicz <arekm@maven.pl> Tested-by: Arkadiusz Miśkiewicz <arekm@maven.pl> Fixes: af8e15cc85a25315 ("oom, oom_reaper: do not enqueue task if it is on the oom_reaper_list head") --- mm/oom_kill.c | 17 +++++++---------- 1 file changed, 7 insertions(+), 10 deletions(-) diff --git a/mm/oom_kill.c b/mm/oom_kill.c index f0e8cd9..057bfee 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -505,14 +505,6 @@ bool __oom_reap_task_mm(struct mm_struct *mm) struct vm_area_struct *vma; bool ret = true; - /* - * Tell all users of get_user/copy_from_user etc... that the content - * is no longer stable. No barriers really needed because unmapping - * should imply barriers already and the reader would hit a page fault - * if it stumbled over a reaped memory. - */ - set_bit(MMF_UNSTABLE, &mm->flags); - for (vma = mm->mmap ; vma; vma = vma->vm_next) { if (!can_madv_dontneed_vma(vma)) continue; @@ -647,8 +639,13 @@ static int oom_reaper(void *unused) static void wake_oom_reaper(struct task_struct *tsk) { - /* tsk is already queued? */ - if (tsk == oom_reaper_list || tsk->oom_reaper_list) + /* + * Tell all users of get_user/copy_from_user etc... that the content + * is no longer stable. No barriers really needed because unmapping + * should imply barriers already and the reader would hit a page fault + * if it stumbled over a reaped memory. + */ + if (test_and_set_bit(MMF_UNSTABLE, &tsk->signal->oom_mm->flags)) return; get_task_struct(tsk); -- 1.8.3.1
next parent reply other threads:[~2019-01-26 13:11 UTC|newest] Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top [not found] <df806a77-3327-9db5-8be2-976fde1c84e5@gmail.com> [not found] ` <20190117122535.njcbqhlmzozdkncw@mikami> [not found] ` <1d36b181-cbaf-6694-1a31-2f7f55d15675@gmail.com> [not found] ` <96ef6615-a5df-30af-b4dc-417a18ca63f1@gmail.com> [not found] ` <1cdbef13-564d-61a6-95f4-579d2cad243d@gmail.com> [not found] ` <20190125163731.GJ50184@devbig004.ftw2.facebook.com> [not found] ` <a95d004a-4358-7efc-6d21-12aac4411b32@gmail.com> [not found] ` <480296c4-ed7a-3265-e84a-298e42a0f1d5@I-love.SAKURA.ne.jp> [not found] ` <6da6ca69-5a6e-a9f6-d091-f89a8488982a@gmail.com> [not found] ` <72aa8863-a534-b8df-6b9e-f69cf4dd5c4d@i-love.sakura.ne.jp> [not found] ` <33a07810-6dbc-36be-5bb6-a279773ccf69@i-love.sakura.ne.jp> [not found] ` <34e97b46-0792-cc66-e0f2-d72576cdec59@i-love.sakura.ne.jp> [not found] ` <2b0c7d6c-c58a-da7d-6f0a-4900694ec2d3@gmail.com> 2019-01-26 13:10 ` Tetsuo Handa [this message] 2019-01-26 13:10 ` [PATCH v2] oom, oom_reaper: do not enqueue same task twice Tetsuo Handa 2019-01-27 8:37 ` Michal Hocko 2019-01-27 10:56 ` Tetsuo Handa 2019-01-27 11:40 ` Michal Hocko 2019-01-27 14:57 ` [PATCH v3] " Tetsuo Handa 2019-01-27 14:57 ` Tetsuo Handa 2019-01-27 16:58 ` Michal Hocko 2019-01-27 23:00 ` Roman Gushchin 2019-01-28 18:15 ` Andrew Morton 2019-01-28 18:42 ` Michal Hocko 2019-01-28 21:53 ` Johannes Weiner 2019-01-29 10:34 ` Tetsuo Handa
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