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From: Oleg Nesterov <oleg@redhat.com>
To: Kirill Tkhai <tkhai@yandex.ru>
Cc: Kirill Tkhai <ktkhai@parallels.com>,
	linux-kernel@vger.kernel.org,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Burke Libbey <burke.libbey@shopify.com>,
	Vladimir Davydov <vdavydov@parallels.com>
Subject: Re: [PATCH] sched: Fix race between task_group and sched_task_group
Date: Wed, 29 Oct 2014 20:21:42 +0100	[thread overview]
Message-ID: <20141029192141.GB16312@redhat.com> (raw)
In-Reply-To: <54505D10.7050809@yandex.ru>

On 10/29, Kirill Tkhai wrote:
>
> On 29.10.2014 01:52, Oleg Nesterov wrote:
>
> > And cgroup_task_migrate() can free ->cgroups via call_rcu(). Of course,
> > in practice raw_spin_lock_irq() should also act as rcu_read_lock(), but
> > we should not rely on implementation details.
>
> Do you mean cgroup_task_migrate()->put_css_set_locked()? It's not
> possible there, because old_cset->refcount is lager than 1. We increment
> it in cgroup_migrate_add_src() and real freeing happens in
> cgroup_migrate_finish(). These functions are around task_migrate(), they
> are pair brackets.

Ah, I see.

> If we've got old_cset in
> cgroup_post_fork()->sched_move_task(), the right sched_task_group will
> be installed by attach->sched_move_task().

Yes, yes, this part is clear.

OK, I think the patch is fine then.

Thanks!

Oleg.


  parent reply	other threads:[~2014-10-29 18:25 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-10-27 10:18 [PATCH] sched: Fix race between task_group and sched_task_group Kirill Tkhai
2014-10-27 12:21 ` Peter Zijlstra
2014-10-27 23:04 ` Oleg Nesterov
2014-10-28  5:24   ` Kirill Tkhai
2014-10-28 22:52     ` Oleg Nesterov
2014-10-29  3:20       ` Kirill Tkhai
2014-10-29  9:16         ` Peter Zijlstra
2014-10-29 11:13           ` Kirill Tkhai
2014-10-29 19:21         ` Oleg Nesterov [this message]
2014-11-04 16:07     ` [tip:sched/urgent] sched: Remove lockdep check in sched_move_task () tip-bot for Kirill Tkhai
2014-10-28 11:01 ` [tip:sched/core] sched: Fix race between task_group and sched_task_group tip-bot for Kirill Tkhai
2015-01-26 23:46 ` [PATCH] " Sasha Levin
2015-01-27  8:48   ` Peter Zijlstra
2015-01-27  9:31   ` Peter Zijlstra

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