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 <[email protected]>
Acked-by: Christoph Lameter <[email protected]>
Cc: Gautham R Shenoy <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/mm/vmstat.c b/mm/vmstat.c
index 1a32130b958c418ec8a018aa676c73bb3d7cde32..db9eabb2c5b3a992a04ac2396bf791b72bbdcf94 100644 (file)
--- 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);