From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
To: "Arkadiusz Miśkiewicz" <a.miskiewicz@gmail.com>
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>
Subject: Re: pids.current with invalid value for hours [5.0.0 rc3 git]
Date: Sat, 26 Jan 2019 10:27:36 +0900 [thread overview]
Message-ID: <480296c4-ed7a-3265-e84a-298e42a0f1d5@I-love.SAKURA.ne.jp> (raw)
In-Reply-To: <a95d004a-4358-7efc-6d21-12aac4411b32@gmail.com>
On 2019/01/26 4:47, Arkadiusz Miśkiewicz wrote:
>> Can you please see whether the problem can be reproduced on the
>> current linux-next?
>>
>> git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
>
> I can reproduce on next (5.0.0-rc3-next-20190125), too:
>
Please try this patch.
Subject: [PATCH v2] memcg: killed threads should not invoke memcg OOM killer
From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>, David Rientjes <rientjes@google.com>
Cc: Michal Hocko <mhocko@kernel.org>, linux-mm@kvack.org,
Kirill Tkhai <ktkhai@virtuozzo.com>,
Linus Torvalds <torvalds@linux-foundation.org>
Message-ID: <01370f70-e1f6-ebe4-b95e-0df21a0bc15e@i-love.sakura.ne.jp>
Date: Tue, 15 Jan 2019 19:17:27 +0900
If $N > $M, a single process with $N threads in a memcg group can easily
kill all $M processes in that memcg group, for mem_cgroup_out_of_memory()
does not check if current thread needs to invoke the memcg OOM killer.
T1@P1 |T2...$N@P1|P2...$M |OOM reaper
----------+----------+----------+----------
# all sleeping
try_charge()
mem_cgroup_out_of_memory()
mutex_lock(oom_lock)
try_charge()
mem_cgroup_out_of_memory()
mutex_lock(oom_lock)
out_of_memory()
select_bad_process()
oom_kill_process(P1)
wake_oom_reaper()
oom_reap_task() # ignores P1
mutex_unlock(oom_lock)
out_of_memory()
select_bad_process(P2...$M)
# all killed by T2...$N@P1
wake_oom_reaper()
oom_reap_task() # ignores P2...$M
mutex_unlock(oom_lock)
We don't need to invoke the memcg OOM killer if current thread was killed
when waiting for oom_lock, for mem_cgroup_oom_synchronize(true) can count
on try_charge() when mem_cgroup_oom_synchronize(true) can not make forward
progress because try_charge() allows already killed/exiting threads to
make forward progress, and memory_max_write() can bail out upon signals.
At first Michal thought that fatal signal check is racy compared to
tsk_is_oom_victim() check. But an experiment showed that trying to call
mark_oom_victim() on all killed thread groups is more racy than fatal
signal check due to task_will_free_mem(current) path in out_of_memory().
Therefore, this patch changes mem_cgroup_out_of_memory() to bail out upon
should_force_charge() == T rather than upon fatal_signal_pending() == T,
for should_force_charge() == T && signal_pending(current) == F at
memory_max_write() can't happen because current thread won't call
memory_max_write() after getting PF_EXITING.
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: Michal Hocko <mhocko@suse.com>
Fixes: 29ef680ae7c2 ("memcg, oom: move out_of_memory back to the charge path")
Fixes: 3100dab2aa09 ("mm: memcontrol: print proper OOM header when no eligible victim left")
Cc: stable@vger.kernel.org # 4.19+
---
mm/memcontrol.c | 19 ++++++++++++++-----
1 file changed, 14 insertions(+), 5 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index af7f18b..79a7d2a 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -248,6 +248,12 @@ enum res_type {
iter != NULL; \
iter = mem_cgroup_iter(NULL, iter, NULL))
+static inline bool should_force_charge(void)
+{
+ return tsk_is_oom_victim(current) || fatal_signal_pending(current) ||
+ (current->flags & PF_EXITING);
+}
+
/* Some nice accessors for the vmpressure. */
struct vmpressure *memcg_to_vmpressure(struct mem_cgroup *memcg)
{
@@ -1389,8 +1395,13 @@ static bool mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask,
};
bool ret;
- mutex_lock(&oom_lock);
- ret = out_of_memory(&oc);
+ if (mutex_lock_killable(&oom_lock))
+ return true;
+ /*
+ * A few threads which were not waiting at mutex_lock_killable() can
+ * fail to bail out. Therefore, check again after holding oom_lock.
+ */
+ ret = should_force_charge() || out_of_memory(&oc);
mutex_unlock(&oom_lock);
return ret;
}
@@ -2209,9 +2220,7 @@ static int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
* bypass the last charges so that they can exit quickly and
* free their memory.
*/
- if (unlikely(tsk_is_oom_victim(current) ||
- fatal_signal_pending(current) ||
- current->flags & PF_EXITING))
+ if (unlikely(should_force_charge()))
goto force;
/*
--
1.8.3.1
next prev parent reply other threads:[~2019-01-26 1:27 UTC|newest]
Thread overview: 22+ 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>
2019-01-25 7:52 ` pids.current with invalid value for hours [5.0.0 rc3 git] Arkadiusz Miśkiewicz
2019-01-25 16:37 ` Tejun Heo
2019-01-25 19:47 ` Arkadiusz Miśkiewicz
2019-01-26 1:27 ` Tetsuo Handa [this message]
2019-01-26 2:41 ` Arkadiusz Miśkiewicz
2019-01-26 6:10 ` Tetsuo Handa
2019-01-26 7:55 ` Tetsuo Handa
2019-01-26 11:09 ` Tetsuo Handa
2019-01-26 11:29 ` Arkadiusz Miśkiewicz
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 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
2019-01-26 1:41 ` pids.current with invalid value for hours [5.0.0 rc3 git] Roman Gushchin
2019-01-26 2:28 ` Arkadiusz Miśkiewicz
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