From db5379a7b5a0e9e9b0bfad517fc6fc9648d60585 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 28 Sep 2011 10:50:57 +1000 Subject: [PATCH] memcg: Fix race condition in memcg_check_events() with this_cpu usage Various code in memcontrol.c () calls this_cpu_read() on the calculations to be done from two different percpu variables, or does an open-coded read-modify-write on a single percpu variable. Disable preemption throughout these operations so that the writes go to the correct palces. [ Added this_cpu to __this_cpu conversion by Johannes ] Signed-off-by: Johannes Weiner Signed-off-by: Steven Rostedt Cc: Greg Thelen Cc: KAMEZAWA Hiroyuki Cc: Balbir Singh Cc: Daisuke Nishimura Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Christoph Lameter Signed-off-by: Andrew Morton <> --- mm/memcontrol.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 44f4311c0722..6aff93c98aca 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -687,8 +687,8 @@ static bool __memcg_event_check(struct mem_cgroup *memcg, int target) { unsigned long val, next; - val = this_cpu_read(memcg->stat->events[MEM_CGROUP_EVENTS_COUNT]); - next = this_cpu_read(memcg->stat->targets[target]); + val = __this_cpu_read(memcg->stat->events[MEM_CGROUP_EVENTS_COUNT]); + next = __this_cpu_read(memcg->stat->targets[target]); /* from time_after() in jiffies.h */ return ((long)next - (long)val < 0); } @@ -697,7 +697,7 @@ static void __mem_cgroup_target_update(struct mem_cgroup *memcg, int target) { unsigned long val, next; - val = this_cpu_read(memcg->stat->events[MEM_CGROUP_EVENTS_COUNT]); + val = __this_cpu_read(memcg->stat->events[MEM_CGROUP_EVENTS_COUNT]); switch (target) { case MEM_CGROUP_TARGET_THRESH: @@ -713,7 +713,7 @@ static void __mem_cgroup_target_update(struct mem_cgroup *memcg, int target) return; } - this_cpu_write(memcg->stat->targets[target], next); + __this_cpu_write(memcg->stat->targets[target], next); } /* @@ -722,6 +722,7 @@ static void __mem_cgroup_target_update(struct mem_cgroup *memcg, int target) */ static void memcg_check_events(struct mem_cgroup *memcg, struct page *page) { + preempt_disable(); /* threshold event is triggered in finer grain than soft limit */ if (unlikely(__memcg_event_check(memcg, MEM_CGROUP_TARGET_THRESH))) { mem_cgroup_threshold(memcg); @@ -741,6 +742,7 @@ static void memcg_check_events(struct mem_cgroup *memcg, struct page *page) } #endif } + preempt_enable(); } static struct mem_cgroup *mem_cgroup_from_cont(struct cgroup *cont) -- 2.39.5