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* [merged] memcg-fix-race-condition-in-memcg_check_events-with-this_cpu-usage.patch removed from -mm tree
From: akpm @ 2011-11-07 20:27 UTC (permalink / raw)
  To: srostedt, balbir, cl, gthelen, hannes, kamezawa.hiroyu, nishimura,
	peterz


The patch titled
     Subject: memcg: Fix race condition in memcg_check_events() with this_cpu usage
has been removed from the -mm tree.  Its filename was
     memcg-fix-race-condition-in-memcg_check_events-with-this_cpu-usage.patch

This patch was dropped because it was merged into mainline or a subsystem tree

The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/

------------------------------------------------------
From: Steven Rostedt <srostedt@redhat.com>
Subject: 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.

[hannes@cmpxchg.org: added this_cpu to __this_cpu conversion]
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Christoph Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/memcontrol.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff -puN mm/memcontrol.c~memcg-fix-race-condition-in-memcg_check_events-with-this_cpu-usage mm/memcontrol.c

--- a/mm/memcontrol.c~memcg-fix-race-condition-in-memcg_check_events-with-this_cpu-usage
+++ a/mm/memcontrol.c
@@ -686,8 +686,8 @@ static bool __memcg_event_check(struct m
 {
 	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);
 }
@@ -696,7 +696,7 @@ static void __mem_cgroup_target_update(s
 {
 	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:
@@ -712,7 +712,7 @@ static void __mem_cgroup_target_update(s
 		return;
 	}
 
-	this_cpu_write(memcg->stat->targets[target], next);
+	__this_cpu_write(memcg->stat->targets[target], next);
 }
 
 /*
@@ -721,6 +721,7 @@ static void __mem_cgroup_target_update(s
  */
 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);
@@ -740,6 +741,7 @@ static void memcg_check_events(struct me
 		}
 #endif
 	}
+	preempt_enable();
 }
 
 static struct mem_cgroup *mem_cgroup_from_cont(struct cgroup *cont)
_

Patches currently in -mm which might be from srostedt@redhat.com are

origin.patch


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