Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler fix from Ingo Molnar:
 "This is a leftover scheduler fix from the v4.2 cycle"

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched: Fix cpu_active_mask/cpu_online_mask race

1 files changed, 8 insertions, 0 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index a585c7b2ccf0..7819725e9da8 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5488,6 +5488,14 @@ static int sched_cpu_active(struct notifier_block *nfb,
         case CPU_STARTING:
                 set_cpu_rq_start_time();
                 return NOTIFY_OK;
+        case CPU_ONLINE:
+                /*
+                 * At this point a starting CPU has marked itself as online via
+                 * set_cpu_online(). But it might not yet have marked itself
+                 * as active, which is essential from here on.
+                 *
+                 * Thus, fall-through and help the starting CPU along.
+                 */
         case CPU_DOWN_FAILED:
                 set_cpu_active((long)hcpu, true);
                 return NOTIFY_OK;