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Subject[PATCH] cpuset: fix possible races in cpu/memory hotplug
Change to cpuset->cpus_allowed and cpuset->mems_allowed should be protected
by callback_mutex, otherwise the reader may read wrong cpus/mems. This is
cpuset's lock rule.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
---
kernel/cpuset.c | 9 ++++++---
1 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index a856788..39f7d94 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -2061,7 +2061,9 @@ static int cpuset_track_online_cpus(struct notifier_block *unused_nb,
}

cgroup_lock();
+ mutex_lock(&callback_mutex);
cpumask_copy(top_cpuset.cpus_allowed, cpu_online_mask);
+ mutex_unlock(&callback_mutex);
scan_for_empty_cpusets(&top_cpuset);
ndoms = generate_sched_domains(&doms, &attr);
cgroup_unlock();
@@ -2084,11 +2086,12 @@ static int cpuset_track_online_nodes(struct notifier_block *self,
cgroup_lock();
switch (action) {
case MEM_ONLINE:
- top_cpuset.mems_allowed = node_states[N_HIGH_MEMORY];
- break;
case MEM_OFFLINE:
+ mutex_lock(&callback_mutex);
top_cpuset.mems_allowed = node_states[N_HIGH_MEMORY];
- scan_for_empty_cpusets(&top_cpuset);
+ mutex_unlock(&callback_mutex);
+ if (action == MEM_OFFLINE)
+ scan_for_empty_cpusets(&top_cpuset);
break;
default:
break;
--
1.5.4.rc3

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