make vmstat cpu-unplug safe

When accessing cpu_online_map, we should prevent dynamic changing
of cpu_online_map by get_online_cpus().

Unfortunately, all_vm_events() doesn't do that.

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: Christoph Lameter <clameter@sgi.com>
Cc: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/mm/vmstat.c b/mm/vmstat.c
index 1a32130b958c..db9eabb2c5b3 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -41,7 +41,9 @@ static void sum_vm_events(unsigned long *ret, cpumask_t *cpumask)
 */
 void all_vm_events(unsigned long *ret)
 {
+        get_online_cpus();
         sum_vm_events(ret, &cpu_online_map);
+        put_online_cpus();
 }
 EXPORT_SYMBOL_GPL(all_vm_events);