keep rd->online and cpu_online_map in sync

It is possible to allow the root-domain cache of online cpus to
become out of sync with the global cpu_online_map.  This is because we
currently trigger removal of cpus too early in the notifier chain.
Other DOWN_PREPARE handlers may in fact run and reconfigure the
root-domain topology, thereby stomping on our own offline handling.

The end result is that rd->online may become out of sync with
cpu_online_map, which results in potential task misrouting.

So change the offline handling to be more tightly coupled with the
global offline process by triggering on CPU_DYING intead of
CPU_DOWN_PREPARE.

Signed-off-by: Gregory Haskins <ghaskins@novell.com>
Cc: Gautham R Shenoy <ego@in.ibm.com>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 2 insertions, 1 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 52b98675acb2..1cb53fb1fe3d 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5881,7 +5881,8 @@ migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu)
                 spin_unlock_irq(&rq->lock);
                 break;
 
-        case CPU_DOWN_PREPARE:
+        case CPU_DYING:
+        case CPU_DYING_FROZEN:
                 /* Update our root-domain */
                 rq = cpu_rq(cpu);
                 spin_lock_irqsave(&rq->lock, flags);