[GIT PULL] leftover scheduler fix from the v4.2 cycle

[Ingo Molnar <mingo@kernel.org>]

Linus,

Please pull the latest sched-urgent-for-linus git tree from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git sched-urgent-for-linus

   # HEAD: dd9d3843755da95f63dd3a376f62b3e45c011210 sched: Fix cpu_active_mask/cpu_online_mask race

This is a leftover scheduler fix from the v4.2 cycle.

 Thanks,

	Ingo

------------------>
Jan H. Schönherr (1):
      sched: Fix cpu_active_mask/cpu_online_mask race


 kernel/sched/core.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 78b4bad10081..e9673433cc01 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5433,6 +5433,14 @@ 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;