Messages in this thread Patch in this message | | | Subject | [PATCH] memcg: Fix race condition in memcg_check_events() with this_cpu usage | From | Steven Rostedt <> | Date | Fri, 23 Sep 2011 20:54:42 -0400 |
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From: Steven Rostedt <srostedt@redhat.com>
The code in memcg_check_events() calls this_cpu_read() on different variables without disabling preemption, and can cause the calculations to be done from two different CPU variables.
Disable preemption throughout the check to keep apples and oranges from becoming a mixed drink.
[ Added this_cpu to __this_cpu conversion by Johannes ]
Cc: Greg Thelen <gthelen@google.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Balbir Singh <balbir@linux.vnet.ibm.com> Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Christoph Lameter <cl@linux.com> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Link: http://lkml.kernel.org/r/20110919212641.015320989@goodmis.org --- mm/memcontrol.c | 10 ++++++---- 1 files changed, 6 insertions(+), 4 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 3508777..f823fc8 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -683,8 +683,8 @@ static bool __memcg_event_check(struct mem_cgroup *mem, int target) { unsigned long val, next; - val = this_cpu_read(mem->stat->events[MEM_CGROUP_EVENTS_COUNT]); - next = this_cpu_read(mem->stat->targets[target]); + val = __this_cpu_read(mem->stat->events[MEM_CGROUP_EVENTS_COUNT]); + next = __this_cpu_read(mem->stat->targets[target]); /* from time_after() in jiffies.h */ return ((long)next - (long)val < 0); } @@ -693,7 +693,7 @@ static void __mem_cgroup_target_update(struct mem_cgroup *mem, int target) { unsigned long val, next; - val = this_cpu_read(mem->stat->events[MEM_CGROUP_EVENTS_COUNT]); + val = __this_cpu_read(mem->stat->events[MEM_CGROUP_EVENTS_COUNT]); switch (target) { case MEM_CGROUP_TARGET_THRESH: @@ -709,7 +709,7 @@ static void __mem_cgroup_target_update(struct mem_cgroup *mem, int target) return; } - this_cpu_write(mem->stat->targets[target], next); + __this_cpu_write(mem->stat->targets[target], next); } /* @@ -718,6 +718,7 @@ static void __mem_cgroup_target_update(struct mem_cgroup *mem, int target) */ static void memcg_check_events(struct mem_cgroup *mem, struct page *page) { + preempt_disable(); /* threshold event is triggered in finer grain than soft limit */ if (unlikely(__memcg_event_check(mem, MEM_CGROUP_TARGET_THRESH))) { mem_cgroup_threshold(mem); @@ -737,6 +738,7 @@ static void memcg_check_events(struct mem_cgroup *mem, struct page *page) } #endif } + preempt_enable(); } static struct mem_cgroup *mem_cgroup_from_cont(struct cgroup *cont) -- 1.7.3.4
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