3.0-stable review patch. If anyone has any objections, please let me know.
------------------
From: Daisuke Nishimura <nishim...@mxp.nes.nec.co.jp>
commit 1f5320d5972aa50d3e8d2b227b636b370e608359 upstream.
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.
Acked-by: Li Zefan <lize...@huawei.com>
Cc: Ben Blum <bb...@andrew.cmu.edu>
Signed-off-by: Daisuke Nishimura <nishim...@mxp.nes.nec.co.jp>
Signed-off-by: Tejun Heo <t...@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
kernel/cgroup.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1800,9 +1800,8 @@ static int cgroup_task_migrate(struct cg
* 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);
return 0;
}
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