From: Tejun Heo <tj@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Sasha Levin <sasha.levin@oracle.com>
Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, mhocko@kernel.org,
cgroups@vger.kernel.org, linux-mm@kvack.org,
vdavydov@parallels.com, kernel-team@fb.com
Subject: Re: [PATCH 1/2] memcg: flatten task_struct->memcg_oom
Date: Wed, 30 Sep 2015 14:54:20 -0400 [thread overview]
Message-ID: <20150930185420.GF2627@mtj.duckdns.org> (raw)
In-Reply-To: <20150921200141.GH13263@mtj.duckdns.org>
On Mon, Sep 21, 2015 at 04:01:41PM -0400, Tejun Heo wrote:
> (cc'ing scheduler folks)
>
> On Sun, Sep 20, 2015 at 10:45:25AM -0400, Sasha Levin wrote:
> > On 09/13/2015 02:59 PM, Tejun Heo wrote:
> > > task_struct->memcg_oom is a sub-struct containing fields which are
> > > used for async memcg oom handling. Most task_struct fields aren't
> > > packaged this way and it can lead to unnecessary alignment paddings.
> > > This patch flattens it.
> > >
> > > * task.memcg_oom.memcg -> task.memcg_in_oom
> > > * task.memcg_oom.gfp_mask -> task.memcg_oom_gfp_mask
> > > * task.memcg_oom.order -> task.memcg_oom_order
> > > * task.memcg_oom.may_oom -> task.memcg_may_oom
> ...
> > I've started seeing these warnings:
> >
> > [1598889.250160] WARNING: CPU: 3 PID: 11648 at include/linux/memcontrol.h:414 handle_mm_fault+0x1020/0x3fa0()
> ...
> > [1598892.247256] dump_stack (lib/dump_stack.c:52)
> > [1598892.249105] warn_slowpath_common (kernel/panic.c:448)
> > [1598892.253202] warn_slowpath_null (kernel/panic.c:482)
> > [1598892.255148] handle_mm_fault (include/linux/memcontrol.h:414 mm/memory.c:3430)
> > [1598892.268151] __do_page_fault (arch/x86/mm/fault.c:1239)
> > [1598892.269022] trace_do_page_fault (arch/x86/mm/fault.c:1331 include/linux/jump_label.h:133 include/linux/context_tracking_state.h:30 include/linux/context_tracking.h:46 arch/x86/mm/fault.c:1332)
> > [1598892.269894] do_async_page_fault (arch/x86/kernel/kvm.c:280)
> > [1598892.270792] async_page_fault (arch/x86/entry/entry_64.S:989)
> >
> > Not sure if it's because of this patch or not, but I haven't seen them before.
>
> So, the only way the patch could have caused the above is if someone
> who isn't the task itself is writing to the bitfields while the task
> is running. Looking through the fields, ->sched_reset_on_fork seems a
> bit suspicious. __sched_setscheduler() looks like it can modify the
> bit while the target task is running. Peter, am I misreading the
> code?
Ping?
--
tejun
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next prev parent reply other threads:[~2015-09-30 18:54 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-13 18:59 [PATCH 1/2] memcg: flatten task_struct->memcg_oom Tejun Heo
2015-09-13 19:00 ` [PATCH v3 2/2] memcg: punt high overage reclaim to return-to-userland path Tejun Heo
2015-09-15 7:47 ` Johannes Weiner
2015-09-15 15:53 ` Tejun Heo
2015-09-15 16:12 ` Johannes Weiner
2015-09-15 16:22 ` Tejun Heo
2015-09-15 16:33 ` Johannes Weiner
2015-09-15 7:37 ` [PATCH 1/2] memcg: flatten task_struct->memcg_oom Johannes Weiner
2015-09-20 14:45 ` Sasha Levin
2015-09-21 20:01 ` Tejun Heo
2015-09-30 18:54 ` Tejun Heo [this message]
2015-11-25 14:43 ` Peter Zijlstra
2015-11-25 15:02 ` Peter Zijlstra
2015-11-25 15:31 ` Andrey Ryabinin
2015-11-25 17:34 ` Dmitry Vyukov
2015-11-25 17:44 ` Peter Zijlstra
2015-12-11 16:25 ` Tejun Heo
2015-12-15 19:22 ` Peter Zijlstra
2015-12-30 9:23 ` [PATCH v4.4-rc7] sched: isolate task_struct bitfields according to synchronization domains Tejun Heo
2015-12-30 20:10 ` Linus Torvalds
2015-12-30 20:17 ` Linus Torvalds
2015-12-30 20:41 ` Tejun Heo
2015-12-30 20:43 ` Linus Torvalds
2016-01-01 2:56 ` [PATCH v4.4-rc7] sched: move sched lock synchronized bitfields in task_struct into ->atomic_flags Tejun Heo
2016-01-06 13:44 ` Tejun Heo
-- strict thread matches above, loose matches on Subject: below --
2015-08-28 22:01 [PATCH 1/2] memcg: flatten task_struct->memcg_oom Tejun Heo
2015-09-01 15:25 ` Michal Hocko
2015-09-02 11:45 ` Vladimir Davydov
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