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mm/memcg: iteration skip memcgs not yet fully initialized

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It is surprising that the mem_cgroup iterator can return memcgs which
have not yet been fully initialized.  By accident (or trial and error?)
this appears not to present an actual problem; but it may be better to
prevent such surprises, by skipping memcgs not yet online.

Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Tejun Heo <tj@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: <stable@vger.kernel.org>	[3.12+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Hugh Dickins 2014-01-23 15:53:32 -08:00 • committed by Linus Torvalds
commit d8ad305597
1 changed files with 2 additions and 4 deletions
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6
mm/memcontrol.c
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@ -1119,10 +1119,8 @@ skip_node:
* protected by css_get and the tree walk is rcu safe. * protected by css_get and the tree walk is rcu safe.
*/ */
if (next_css) { if (next_css) {
struct mem_cgroup *mem = mem_cgroup_from_css(next_css); if ((next_css->flags & CSS_ONLINE) && css_tryget(next_css))
return mem_cgroup_from_css(next_css);
if (css_tryget(&mem->css))
return mem;
else { else {
prev_css = next_css; prev_css = next_css;
goto skip_node; goto skip_node;