From: Peter Zijlstra Date: Wed, 5 Sep 2012 22:03:50 +0000 (+0200) Subject: sched: Fix load avg vs. cpu-hotplug X-Git-Tag: firefly_0821_release~3680^2~1997^2~8 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=08bedae1d0acd8c9baf514fb69fa199d0c8345f6;p=firefly-linux-kernel-4.4.55.git sched: Fix load avg vs. cpu-hotplug 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 Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/1346882630.2600.59.camel@twins Signed-off-by: Ingo Molnar --- diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 8b51b2d9b1fd..ba144b121f3d 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -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