Commit 08bedae1 authored Sep 06, 2012 by Peter Zijlstra Committed by Ingo Molnar Sep 13, 2012

sched: Fix load avg vs. cpu-hotplug



Commit f319da0c ("sched: Fix load avg vs cpu-hotplug") was an
incomplete fix:

In particular, the problem is that at the point it calls
calc_load_migrate() nr_running := 1 (the stopper thread), so move the
call to CPU_DEAD where we're sure that nr_running := 0.

Also note that we can call calc_load_migrate() without serialization, we
know the state of rq is stable since its cpu is dead, and we modify the
global state using appropriate atomic ops.

Suggested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1346882630.2600.59.camel@twins


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent f3e94786

kernel/sched/core.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -5048,7 +5048,9 @@ migration_call(struct notifier_block nfb, unsigned long action, void hcpu)
		migrate_tasks(cpu);
		BUG_ON(rq->nr_running != 1); /* the migration thread */
		raw_spin_unlock_irqrestore(&rq->lock, flags);
		break;

		case CPU_DEAD:
		calc_load_migrate(rq);
		break;
		#endif

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