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From: Tejun Heo <tj@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>,
	Ingo Molnar <mingo@redhat.com>,
	Sasha Levin <sasha.levin@oracle.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Michal Hocko <mhocko@kernel.org>,
	cgroups <cgroups@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	Vladimir Davydov <vdavydov@parallels.com>,
	kernel-team <kernel-team@fb.com>,
	Dmitry Vyukov <dvyukov@google.com>,
	Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH v4.4-rc7] sched: move sched lock synchronized bitfields in task_struct into ->atomic_flags
Date: Wed, 6 Jan 2016 08:44:53 -0500	[thread overview]
Message-ID: <20160106134453.GB29797@mtj.duckdns.org> (raw)
In-Reply-To: <20160101025628.GA3660@htj.duckdns.org>

On Thu, Dec 31, 2015 at 09:56:28PM -0500, Tejun Heo wrote:
> task_struct has a cluster of unsigned bitfields.  Some are updated
> under scheduler locks while others are updated only by the task
> itself.  Currently, the two classes of bitfields aren't distinguished
> and end up on the same word which can lead to clobbering when there
> are simultaneous read-modify-write attempts.  While difficult to prove
> definitely, it's likely that the resulting inconsistency led to low
> frqeuency failures such as wrong memcg_may_oom state or loadavg
> underflow due to clobbered sched_contributes_to_load.

Ping.

-- 
tejun

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WARNING: multiple messages have this Message-ID (diff)
From: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
To: Linus Torvalds
	<torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
Cc: Andrey Ryabinin
	<ryabinin.a.a-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	Ingo Molnar <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	Sasha Levin <sasha.levin-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>,
	Andrew Morton
	<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
	Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>,
	Michal Hocko <mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
	cgroups <cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	"linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org"
	<linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org>,
	Vladimir Davydov
	<vdavydov-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>,
	kernel-team <kernel-team-b10kYP2dOMg@public.gmane.org>,
	Dmitry Vyukov <dvyukov-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
	Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
Subject: Re: [PATCH v4.4-rc7] sched: move sched lock synchronized bitfields in task_struct into ->atomic_flags
Date: Wed, 6 Jan 2016 08:44:53 -0500	[thread overview]
Message-ID: <20160106134453.GB29797@mtj.duckdns.org> (raw)
In-Reply-To: <20160101025628.GA3660-piEFEHQLUPpN0TnZuCh8vA@public.gmane.org>

On Thu, Dec 31, 2015 at 09:56:28PM -0500, Tejun Heo wrote:
> task_struct has a cluster of unsigned bitfields.  Some are updated
> under scheduler locks while others are updated only by the task
> itself.  Currently, the two classes of bitfields aren't distinguished
> and end up on the same word which can lead to clobbering when there
> are simultaneous read-modify-write attempts.  While difficult to prove
> definitely, it's likely that the resulting inconsistency led to low
> frqeuency failures such as wrong memcg_may_oom state or loadavg
> underflow due to clobbered sched_contributes_to_load.

Ping.

-- 
tejun

  reply	other threads:[~2016-01-06 13:44 UTC|newest]

Thread overview: 43+ 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 18:59 ` 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  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 16:22           ` Tejun Heo
2015-09-15 16:33           ` Johannes Weiner
2015-09-15 16:33             ` Johannes Weiner
2015-09-15  7:37 ` [PATCH 1/2] memcg: flatten task_struct->memcg_oom Johannes Weiner
2015-09-15  7:37   ` Johannes Weiner
2015-09-20 14:45 ` Sasha Levin
2015-09-20 14:45   ` Sasha Levin
2015-09-21 20:01   ` Tejun Heo
2015-09-21 20:01     ` Tejun Heo
2015-09-30 18:54     ` Tejun Heo
2015-09-30 18:54       ` Tejun Heo
2015-11-25 14:43     ` Peter Zijlstra
2015-11-25 14:43       ` Peter Zijlstra
2015-11-25 15:02       ` 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 17:34             ` Dmitry Vyukov
2015-11-25 17:44           ` Peter Zijlstra
2015-12-11 16:25             ` Tejun Heo
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 20:10                     ` Linus Torvalds
2015-12-30 20:17                     ` Linus Torvalds
2015-12-30 20:41                     ` Tejun Heo
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
2016-01-01  2:56                       ` Tejun Heo
2016-01-06 13:44                       ` Tejun Heo [this message]
2016-01-06 13:44                         ` Tejun Heo
2016-01-06 18:48         ` [tip:sched/core] sched/core: Fix unserialized r-m-w scribbling stuff tip-bot for Peter Zijlstra
2016-01-06 20:17           ` Tejun Heo

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