| From | Greg Kroah-Hartman <> | Subject | [ 107/122] sched: Fix load avg vs. cpu-hotplug | Date | Thu, 11 Oct 2012 07:54:33 +0900 |
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3.6-stable review patch. If anyone has any objections, please let me know.
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From: Peter Zijlstra <peterz@infradead.org>
commit 08bedae1d0acd8c9baf514fb69fa199d0c8345f6 upstream.
Commit f319da0c68 ("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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- kernel/sched/core.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5604,7 +5604,9 @@ migration_call(struct notifier_block *nf 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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