Messages in this thread Patch in this message | | | Date | Wed, 12 Feb 2014 17:26:46 -0800 (PST) | From | Hugh Dickins <> | Subject | [PATCH 1/2] memcg: fix endless loop in __mem_cgroup_iter_next |
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Commit 0eef615665ed ("memcg: fix css reference leak and endless loop in mem_cgroup_iter") got the interaction with the commit a few before it d8ad30559715 ("mm/memcg: iteration skip memcgs not yet fully initialized") slightly wrong, and we didn't notice at the time.
It's elusive, and harder to get than the original, but for a couple of days before rc1, I several times saw a endless loop similar to that supposedly being fixed.
This time it was a tighter loop in __mem_cgroup_iter_next(): because we can get here when our root has already been offlined, and the ordering of conditions was such that we then just cycled around forever.
Fixes: 0eef615665ed ("memcg: fix css reference leak and endless loop in mem_cgroup_iter") Signed-off-by: Hugh Dickins <hughd@google.com> Cc: stable@vger.kernel.org # 3.12+ --- Of course I'd have preferred to send this before that commit went through to -stable, but priorities kept preempting; I did wonder whether to ask GregKH to delay it, but decided it's not serious enough to trouble him, just go with the flow of stable fixing stable.
mm/memcontrol.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- 3.14-rc2/mm/memcontrol.c 2014-02-02 18:49:07.897302115 -0800 +++ linux/mm/memcontrol.c 2014-02-12 11:55:02.836035004 -0800 @@ -1127,8 +1127,8 @@ skip_node: * skipping css reference should be safe. */ if (next_css) { - if ((next_css->flags & CSS_ONLINE) && - (next_css == &root->css || css_tryget(next_css))) + if ((next_css == &root->css) || + ((next_css->flags & CSS_ONLINE) && css_tryget(next_css))) return mem_cgroup_from_css(next_css); prev_css = next_css;
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