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Commit 9abf24d4 authored by Srikar Dronamraju's avatar Srikar Dronamraju Committed by Ingo Molnar
Browse files

sched: Check sched_domain before computing group power 



After commit 863bffc8 ("sched/fair: Fix group power_orig
computation"), we can dereference rq->sd before it is set.

Fix this by falling back to power_of() in this case and add a comment
explaining things.

Signed-off-by: default avatarSrikar Dronamraju <srikar@linux.vnet.ibm.com>
[ Added comment and tweaked patch. ]
Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Cc: mikey@neuling.org
Link: http://lkml.kernel.org/r/20131113151718.GN21461@twins.programming.kicks-ass.net


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 7486d6da

kernel/sched/fair.c

+24 −3
Original line number Diff line number Diff line
@@ -5379,10 +5379,31 @@ void update_group_power(struct sched_domain *sd, int cpu) 
		 */



		for_each_cpu(cpu, sched_group_cpus(sdg)) {

			struct sched_group *sg = cpu_rq(cpu)->sd->groups;

			struct sched_group_power *sgp;

			struct rq *rq = cpu_rq(cpu);



			/*

			 * build_sched_domains() -> init_sched_groups_power()

			 * gets here before we've attached the domains to the

			 * runqueues.

			 *

			 * Use power_of(), which is set irrespective of domains

			 * in update_cpu_power().

			 *

			 * This avoids power/power_orig from being 0 and

			 * causing divide-by-zero issues on boot.

			 *

			 * Runtime updates will correct power_orig.

			 */

			if (unlikely(!rq->sd)) {

				power_orig += power_of(cpu);

				power += power_of(cpu);

				continue;

			}



			power_orig += sg->sgp->power_orig;

			power += sg->sgp->power;

			sgp = rq->sd->groups->sgp;

			power_orig += sgp->power_orig;

			power += sgp->power;

		}

	} else  {

		/*