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cgroup: notify_on_release may not be triggered in some cases 

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: <stable@vger.kernel.org> # v3.0.x and later
Acked-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Daisuke Nishimura 2012-10-04 16:37:16 +09:00 committed by Tejun Heo
parent ddffeb8c4d
commit 1f5320d597
1 changed files with 1 additions and 2 deletions
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3
kernel/cgroup.c
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@ -1962,9 +1962,8 @@ static void cgroup_task_migrate(struct cgroup *cgrp, struct cgroup *oldcgrp,
* trading it for newcg is protected by cgroup_mutex, we're safe to drop
* it here; it will be freed under RCU.
*/
put_css_set(oldcg);
set_bit(CGRP_RELEASABLE, &oldcgrp->flags);
put_css_set(oldcg);
}
/**