Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 3.13 006/149] memcg: fix endless loop in __mem_cgroup_iter_next() | Date | Thu, 20 Mar 2014 17:02:49 -0700 |
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3.13-stable review patch. If anyone has any objections, please let me know.
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From: Hugh Dickins <hughd@google.com>
commit ce48225fe3b1b0d1fc9fceb96ac3d8a879e45114 upstream.
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> Acked-by: Michal Hocko <mhocko@suse.cz> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Greg Thelen <gthelen@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- mm/memcontrol.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1108,8 +1108,8 @@ 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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