path: root/mm
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authorGreg Thelen <gthelen@google.com>2013-09-11 14:23:08 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-09-26 17:15:50 -0700
commit5a20c03a7dc54e3eea59b0be6027b124235b6761 (patch)
tree77683c26bbafea4d3f56c71d7bccaf825c45f154 /mm
parent55ee351dc444224f7bb9697a98b2d06e8625f491 (diff)
memcg: fix multiple large threshold notifications
commit 2bff24a3707093c435ab3241c47dcdb5f16e432b upstream. A memory cgroup with (1) multiple threshold notifications and (2) at least one threshold >=2G was not reliable. Specifically the notifications would either not fire or would not fire in the proper order. The __mem_cgroup_threshold() signaling logic depends on keeping 64 bit thresholds in sorted order. mem_cgroup_usage_register_event() sorts them with compare_thresholds(), which returns the difference of two 64 bit thresholds as an int. If the difference is positive but has bit[31] set, then sort() treats the difference as negative and breaks sort order. This fix compares the two arbitrary 64 bit thresholds returning the classic -1, 0, 1 result. The test below sets two notifications (at 0x1000 and 0x81001000): cd /sys/fs/cgroup/memory mkdir x for x in 4096 2164264960; do cgroup_event_listener x/memory.usage_in_bytes $x | sed "s/^/$x listener:/" & done echo $$ > x/cgroup.procs anon_leaker 500M v3.11-rc7 fails to signal the 4096 event listener: Leaking... Done leaking pages. Patched v3.11-rc7 properly notifies: Leaking... 4096 listener:2013:8:31:14:13:36 Done leaking pages. The fixed bug is old. It appears to date back to the introduction of memcg threshold notifications in v2.6.34-rc1-116-g2e72b6347c94 "memcg: implement memory thresholds" Signed-off-by: Greg Thelen <gthelen@google.com> Acked-by: Michal Hocko <mhocko@suse.cz> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> 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>
Diffstat (limited to 'mm')
1 files changed, 7 insertions, 1 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 81c275b3afed..9c364428cf71 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4349,7 +4349,13 @@ static int compare_thresholds(const void *a, const void *b)
const struct mem_cgroup_threshold *_a = a;
const struct mem_cgroup_threshold *_b = b;
- return _a->threshold - _b->threshold;
+ if (_a->threshold > _b->threshold)
+ return 1;
+ if (_a->threshold < _b->threshold)
+ return -1;
+ return 0;
static int mem_cgroup_oom_notify_cb(struct mem_cgroup *memcg)