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authorTejun Heo <tj@kernel.org>2016-01-21 23:31:11 +0300
committerTejun Heo <tj@kernel.org>2016-01-22 18:42:57 +0300
commitaa226ff4a1ce79f229c6b7a4c0a14e17fececd01 (patch)
tree1db4c5f20ffafca177de0bbe26beddcc60e26f93 /include/linux/cgroup-defs.h
parente93ad19d05648397ef3bcb838d26aec06c245dc0 (diff)
downloadlinux-aa226ff4a1ce79f229c6b7a4c0a14e17fececd01.tar.xz
cgroup: make sure a parent css isn't offlined before its children
There are three subsystem callbacks in css shutdown path - css_offline(), css_released() and css_free(). Except for css_released(), cgroup core didn't guarantee the order of invocation. css_offline() or css_free() could be called on a parent css before its children. This behavior is unexpected and led to bugs in cpu and memory controller. This patch updates offline path so that a parent css is never offlined before its children. Each css keeps online_cnt which reaches zero iff itself and all its children are offline and offline_css() is invoked only after online_cnt reaches zero. This fixes the memory controller bug and allows the fix for cpu controller. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-and-tested-by: Christian Borntraeger <borntraeger@de.ibm.com> Reported-by: Brian Christiansen <brian.o.christiansen@gmail.com> Link: http://lkml.kernel.org/g/5698A023.9070703@de.ibm.com Link: http://lkml.kernel.org/g/CAKB58ikDkzc8REt31WBkD99+hxNzjK4+FBmhkgS+NVrC9vjMSg@mail.gmail.com Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: stable@vger.kernel.org
Diffstat (limited to 'include/linux/cgroup-defs.h')
-rw-r--r--include/linux/cgroup-defs.h6
1 files changed, 6 insertions, 0 deletions
diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
index 7f540f7f588d..789471dba6fb 100644
--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -127,6 +127,12 @@ struct cgroup_subsys_state {
*/
u64 serial_nr;
+ /*
+ * Incremented by online self and children. Used to guarantee that
+ * parents are not offlined before their children.
+ */
+ atomic_t online_cnt;
+
/* percpu_ref killing and RCU release */
struct rcu_head rcu_head;
struct work_struct destroy_work;