From: Andrew Morton <akpm@linux-foundation.org>
To: Michal Hocko <mhocko@suse.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
linux-mm@kvack.org, xiyou.wangcong@gmail.com,
dave.hansen@intel.com, hannes@cmpxchg.org, mgorman@suse.de,
vbabka@suse.cz
Subject: Re: [PATCH] mm,page_alloc: Serialize warn_alloc() if schedulable.
Date: Thu, 1 Jun 2017 15:10:22 -0700 [thread overview]
Message-ID: <20170601151022.b17716472adbf0e6d51fb011@linux-foundation.org> (raw)
In-Reply-To: <20170601132808.GD9091@dhcp22.suse.cz>
On Thu, 1 Jun 2017 15:28:08 +0200 Michal Hocko <mhocko@suse.com> wrote:
> On Thu 01-06-17 22:11:13, Tetsuo Handa wrote:
> > Michal Hocko wrote:
> > > On Thu 01-06-17 20:43:47, Tetsuo Handa wrote:
> > > > Cong Wang has reported a lockup when running LTP memcg_stress test [1].
> > >
> > > This seems to be on an old and not pristine kernel. Does it happen also
> > > on the vanilla up-to-date kernel?
> >
> > 4.9 is not an old kernel! It might be close to the kernel version which
> > enterprise distributions would choose for their next long term supported
> > version.
> >
> > And please stop saying "can you reproduce your problem with latest
> > linux-next (or at least latest linux)?" Not everybody can use the vanilla
> > up-to-date kernel!
>
> The changelog mentioned that the source of stalls is not clear so this
> might be out-of-tree patches doing something wrong and dump_stack
> showing up just because it is called often. This wouldn't be the first
> time I have seen something like that. I am not really keen on adding
> heavy lifting for something that is not clearly debugged and based on
> hand waving and speculations.
I'm thinking we should serialize warn_alloc anyway, to prevent the
output from concurrent calls getting all jumbled together?
I'm not sure I buy the "this isn't a mainline kernel" thing.
warn_alloc() obviously isn't very robust, but we'd prefer that it be
robust to peculiar situations, wild-n-wacky kernel patches, etc. It's
a low-level thing and it should Just Work.
I do think ratelimiting will be OK - if the kernel is producing such a
vast stream of warn_alloc() output then nobody is going to be reading
it all anyway. Probably just the first one is enough for operators to
understand what's going wrong.
So... I think both. ratelimit *and* serialize. Perhaps a simple but
suitable way of doing that is simply to disallow concurrent warn_allocs:
/* comment goes here */
if (test_and_set_bit(0, &foo))
return;
...
clear_bit(0, &foo);
or whatever?
(And if we do decide to go with "mm,page_alloc: Serialize warn_alloc()
if schedulable", please do add code comments explaining what's going on)
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next prev parent reply other threads:[~2017-06-01 22:10 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-01 11:43 [PATCH] mm,page_alloc: Serialize warn_alloc() if schedulable Tetsuo Handa
2017-06-01 11:59 ` Michal Hocko
2017-06-01 13:11 ` Tetsuo Handa
2017-06-01 13:28 ` Michal Hocko
2017-06-01 22:10 ` Andrew Morton [this message]
2017-06-02 7:18 ` Michal Hocko
2017-06-02 11:13 ` Tetsuo Handa
2017-06-02 12:15 ` Michal Hocko
2017-06-02 17:13 ` Tetsuo Handa
2017-06-02 21:57 ` Cong Wang
2017-06-04 8:58 ` Tetsuo Handa
2017-06-04 15:05 ` Michal Hocko
2017-06-04 21:43 ` Tetsuo Handa
2017-06-05 5:37 ` Michal Hocko
2017-06-05 18:15 ` Cong Wang
2017-06-06 9:17 ` Michal Hocko
2017-06-05 18:25 ` Cong Wang
2017-06-22 10:35 ` Tetsuo Handa
2017-06-22 22:53 ` Cong Wang
2017-06-02 16:59 ` Cong Wang
2017-06-02 19:59 ` Andrew Morton
2017-06-03 2:57 ` Tetsuo Handa
2017-06-03 7:32 ` Michal Hocko
2017-06-03 8:36 ` Tetsuo Handa
2017-06-05 7:10 ` Sergey Senozhatsky
2017-06-05 9:36 ` Sergey Senozhatsky
2017-06-05 15:02 ` Tetsuo Handa
2017-06-03 13:21 ` Tetsuo Handa
2017-07-08 4:59 ` Tetsuo Handa
2017-07-10 13:21 ` Michal Hocko
2017-07-10 13:54 ` Tetsuo Handa
2017-07-10 14:14 ` Michal Hocko
2017-07-11 13:10 ` Tetsuo Handa
2017-07-11 13:49 ` Michal Hocko
2017-07-11 14:58 ` Petr Mladek
2017-07-11 22:06 ` Tetsuo Handa
2017-07-12 8:54 ` Michal Hocko
2017-07-12 12:23 ` Tetsuo Handa
2017-07-12 12:41 ` Michal Hocko
2017-07-14 12:30 ` Tetsuo Handa
2017-07-14 12:48 ` Michal Hocko
2017-08-09 6:14 ` Tetsuo Handa
2017-08-09 13:01 ` Tetsuo Handa
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