I think this bugfix is needed before going ahead. thoughts?
==
>From 2cb491a41782b39aae9f6fe7255b9159ac6c1563 Mon Sep 17 00:00:00 2001
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Date: Fri, 13 Jan 2012 14:27:20 +0900
Subject: [PATCH 2/7] memcg: add memory barrier for checking account move.
At starting move_account(), source memcg's per-cpu variable
MEM_CGROUP_ON_MOVE is set. The page status update
routine check it under rcu_read_lock(). But there is no memory
barrier. This patch adds one.
Signed-off-by: KAMAZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
---
mm/memcontrol.c | 5 ++++-
1 files changed, 4 insertions(+), 1 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 08b988d..9019069 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1256,8 +1256,10 @@ static void mem_cgroup_start_move(struct mem_cgroup *memcg)
get_online_cpus();
spin_lock(&memcg->pcp_counter_lock);
- for_each_online_cpu(cpu)
+ for_each_online_cpu(cpu) {
per_cpu(memcg->stat->count[MEM_CGROUP_ON_MOVE], cpu) += 1;
+ smp_wmb();
+ }
memcg->nocpu_base.count[MEM_CGROUP_ON_MOVE] += 1;
spin_unlock(&memcg->pcp_counter_lock);
put_online_cpus();
@@ -1294,6 +1296,7 @@ static void mem_cgroup_end_move(struct mem_cgroup *memcg)
static bool mem_cgroup_stealed(struct mem_cgroup *memcg)
{
VM_BUG_ON(!rcu_read_lock_held());
+ smp_rmb();
return this_cpu_read(memcg->stat->count[MEM_CGROUP_ON_MOVE]) > 0;
}
--
1.7.4.1
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