Re: [REGRESSION] cgroup: notify_on_release may not be triggered in some cases

[Tejun Heo <tj@kernel.org>]

Hello,

On Thu, Oct 04, 2012 at 04:37:16PM +0900, Daisuke Nishimura wrote:
> notify_on_release must be triggered when the last process in a cgroup is
> move to another. But if the first(and only) process in a cgroup is moved to
> another, notify_on_release is not triggered.
> 
> 	# mkdir /cgroup/cpu/SRC
> 	# mkdir /cgroup/cpu/DST
> 	#
> 	# echo 1 >/cgroup/cpu/SRC/notify_on_release
> 	# echo 1 >/cgroup/cpu/DST/notify_on_release
> 	#
> 	# sleep 300 &
> 	[1] 8629
> 	#
> 	# echo 8629 >/cgroup/cpu/SRC/tasks
> 	# echo 8629 >/cgroup/cpu/DST/tasks
> 	-> notify_on_release for /SRC must be triggered at this point,
> 	   but it isn't.
> 
> This is because put_css_set() is called before setting CGRP_RELEASABLE
> in cgroup_task_migrate(), and is a regression introduce by the
> commit:74a1166d(cgroups: make procs file writable), which was merged
> into v3.0.
> 
> Cc: Ben Blum <bblum@andrew.cmu.edu>
> Cc: Tejun Heo <tj@kernel.org>
> Cc: Li Zefan <lizefan@huawei.com>
> Cc: <stable@vger.kernel.org> # v3.0.x and later
> Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>

Applied to cgroup/for-3.7-fixes w/ Li's ack added.

Thanks!

-- 
tejun