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>
Cc: Paul Menage <menage@google.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index ee5ec38..3173795 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -2070,7 +2070,9 @@
}
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();
@@ -2093,11 +2095,12 @@
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;