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Commit ca464d69 authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
Browse files

memcg: let css_get_next() rely upon rcu_read_lock() 



Remove lock and unlock around css_get_next()'s call to idr_get_next().
memcg iterators (only users of css_get_next) already did rcu_read_lock(),
and its comment demands that; but add a WARN_ON_ONCE to make sure of it.

Signed-off-by: default avatarHugh Dickins <hughd@google.com>
Acked-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: default avatarLi Zefan <lizf@cn.fujitsu.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 42aee6c4

kernel/cgroup.c

+2 −3
Original line number Diff line number Diff line
@@ -5033,6 +5033,8 @@ css_get_next(struct cgroup_subsys *ss, int id, 
		return NULL;



	BUG_ON(!ss->use_id);

	WARN_ON_ONCE(!rcu_read_lock_held());



	/* fill start point for scan */

	tmpid = id;

	while (1) {
@@ -5040,10 +5042,7 @@ css_get_next(struct cgroup_subsys *ss, int id, 
		 * scan next entry from bitmap(tree), tmpid is updated after

		 * idr_get_next().

		 */

		spin_lock(&ss->id_lock);

		tmp = idr_get_next(&ss->idr, &tmpid);

		spin_unlock(&ss->id_lock);



		if (!tmp)

			break;

		if (tmp->depth >= depth && tmp->stack[depth] == rootid) {