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From: Tejun Heo <tj@kernel.org>
To: Michal Hocko <mhocko@kernel.org>
Cc: Petr Mladek <pmladek@suse.com>,
	cgroups@vger.kernel.org, Cyril Hrubis <chrubis@suse.cz>,
	linux-kernel@vger.kernel.org,
	Johannes Weiner <hannes@cmpxchg.org>
Subject: Re: [BUG] cgroup/workques/fork: deadlock when moving cgroups
Date: Wed, 13 Apr 2016 15:37:34 -0400	[thread overview]
Message-ID: <20160413193734.GC20142@htj.duckdns.org> (raw)
In-Reply-To: <20160413192313.GA30260@dhcp22.suse.cz>

Hello, Michal.

On Wed, Apr 13, 2016 at 09:23:14PM +0200, Michal Hocko wrote:
> I think we can live without lru_add_drain_all() in the migration path.
> We are talking about 4 pagevecs so 56 pages. The charge migration is

Ah, nice.

> racy anyway. What concerns me more is how all this is fragile. It sounds
> just too easy to add a dependency on per-cpu sync work later and
> reintroduce this issue which is quite hard to detect.
> Cannot we come up with something more robust?  Or at least warn when we
> try to use per-cpu workers with problematic locks held?

Yeah, workqueue does limited lockdep annotation but it doesn't
integrate fully with the rest of dependency tracking.  It'd be nice to
have that.  Don't know how to tho.

Thanks.

-- 
tejun

  parent reply	other threads:[~2016-04-13 19:48 UTC|newest]

Thread overview: 56+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-04-13  9:42 [BUG] cgroup/workques/fork: deadlock when moving cgroups Petr Mladek
2016-04-13 18:33 ` Tejun Heo
2016-04-13 18:33   ` Tejun Heo
2016-04-13 18:57   ` Tejun Heo
2016-04-13 18:57     ` Tejun Heo
2016-04-13 19:23   ` Michal Hocko
2016-04-13 19:23     ` Michal Hocko
2016-04-13 19:28     ` Michal Hocko
2016-04-13 19:28       ` Michal Hocko
2016-04-13 19:37     ` Tejun Heo [this message]
2016-04-13 19:48       ` Michal Hocko
2016-04-14  7:06         ` Michal Hocko
2016-04-14  7:06           ` Michal Hocko
2016-04-14 15:32           ` Tejun Heo
2016-04-14 15:32             ` Tejun Heo
2016-04-14 17:50     ` Johannes Weiner
2016-04-15  7:06       ` Michal Hocko
2016-04-15 14:38         ` Tejun Heo
2016-04-15 14:38           ` Tejun Heo
2016-04-15 15:08           ` Michal Hocko
2016-04-15 15:08             ` Michal Hocko
2016-04-15 15:25             ` Tejun Heo
2016-04-15 15:25               ` Tejun Heo
2016-04-17 12:00               ` Michal Hocko
2016-04-17 12:00                 ` Michal Hocko
2016-04-18 14:40           ` Petr Mladek
2016-04-18 14:40             ` Petr Mladek
2016-04-19 14:01             ` Michal Hocko
2016-04-19 14:01               ` Michal Hocko
2016-04-19 15:39               ` Petr Mladek
2016-04-15 19:17       ` [PATCH for-4.6-fixes] memcg: remove lru_add_drain_all() invocation from mem_cgroup_move_charge() Tejun Heo
2016-04-17 12:07         ` Michal Hocko
2016-04-17 12:07           ` Michal Hocko
2016-04-20 21:29           ` Tejun Heo
2016-04-20 21:29             ` Tejun Heo
2016-04-21  3:27             ` Michal Hocko
2016-04-21  3:27               ` Michal Hocko
2016-04-21 15:00               ` Petr Mladek
2016-04-21 15:00                 ` Petr Mladek
2016-04-21 15:51                 ` Tejun Heo
2016-04-21 23:06           ` [PATCH 1/2] cgroup, cpuset: replace cpuset_post_attach_flush() with cgroup_subsys->post_attach callback Tejun Heo
2016-04-21 23:06             ` Tejun Heo
2016-04-21 23:09             ` [PATCH 2/2] memcg: relocate charge moving from ->attach to ->post_attach Tejun Heo
2016-04-21 23:09               ` Tejun Heo
2016-04-22 13:57               ` Petr Mladek
2016-04-22 13:57                 ` Petr Mladek
2016-04-25  8:25               ` Michal Hocko
2016-04-25  8:25                 ` Michal Hocko
2016-04-25 19:42                 ` Tejun Heo
2016-04-25 19:42                   ` Tejun Heo
2016-04-25 19:44               ` Tejun Heo
2016-04-25 19:44                 ` Tejun Heo
2016-04-21 23:11             ` [PATCH 1/2] cgroup, cpuset: replace cpuset_post_attach_flush() with cgroup_subsys->post_attach callback Tejun Heo
2016-04-21 23:11               ` Tejun Heo
2016-04-21 15:56         ` [PATCH for-4.6-fixes] memcg: remove lru_add_drain_all() invocation from mem_cgroup_move_charge() Tejun Heo
2016-04-21 15:56           ` Tejun Heo

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