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From: Oleg Nesterov <oleg@redhat.com>
To: Kirill Tkhai <ktkhai@parallels.com>
Cc: 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>,
	Kirill Tkhai <tkhai@yandex.ru>
Subject: Re: [PATCH] sched: Fix race between task_group and sched_task_group
Date: Tue, 28 Oct 2014 00:04:27 +0100	[thread overview]
Message-ID: <20141027230427.GA18454@redhat.com> (raw)
In-Reply-To: <1414405105.19914.169.camel@tkhai>

On 10/27, Kirill Tkhai wrote:
>
> +static void cpu_cgroup_fork(struct task_struct *task)
> +{
> +	sched_move_task(task);
> +}
> +
>  static int cpu_cgroup_can_attach(struct cgroup_subsys_state *css,
>  				 struct cgroup_taskset *tset)
>  {
> @@ -8205,6 +8210,7 @@ struct cgroup_subsys cpu_cgrp_subsys = {
>  	.css_free	= cpu_cgroup_css_free,
>  	.css_online	= cpu_cgroup_css_online,
>  	.css_offline	= cpu_cgroup_css_offline,
> +	.fork		= cpu_cgroup_fork,

Agreed, but it seems that sched_move_task() -> task_css_check() can
complain if CONFIG_PROVE_RCU...

cpu_cgroup_exit() too calls sched_move_task() without any lock, but
there is the PF_EXITING check and init_css_set can't go away.

perhaps sched_move_task() should just take rcu_read_lock() and use
task_css() ? This lockdep_is_held(siglock) looks ugly, and iiuc we
need it to shut up the warning if autogroup_move_group() is the caller.

Oleg.


  parent reply	other threads:[~2014-10-27 22:08 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 [this message]
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
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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