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Commit a75f1d1a authored by Blagovest Kolenichev's avatar Blagovest Kolenichev
Browse files

Revert "ANDROID: sched/fair: prevent possible infinite loop in sched_group_energy" 



This reverts commit 727eafb4.

This is a preparation change for merging android-4.14 commit
e709f59a into msm-4.14 branch.
The reverted change is committed already as:

536e7d5d sched/fair: prevent possible infinite loop in compute_energy()

Change-Id: I1f44e4b332b973f71d8e5945b7557b8c2e98030f
Signed-off-by: default avatarBlagovest Kolenichev <bkolenichev@codeaurora.org>
parent 7d77e18d

kernel/sched/fair.c

+2 −30
Original line number Diff line number Diff line
@@ -6238,21 +6238,11 @@ static int compute_energy(struct energy_env *eenv) 
	int cpu;

	struct cpumask visit_cpus;

	struct sched_group *sg;

	int cpu_count;



	WARN_ON(!eenv->sg_top->sge);



	cpumask_copy(&visit_cpus, sched_group_span(eenv->sg_top));

	/* If a cpu is hotplugged in while we are in this function, it does

	 * not appear in the existing visit_cpus mask which came from the

	 * sched_group pointer of the sched_domain pointed at by sd_ea for

	 * either the prev or next cpu and was dereferenced in

	 * select_energy_cpu_idx.

	 * Since we will dereference sd_scs later as we iterate through the

	 * CPUs we expect to visit, new CPUs can be present which are not in

	 * the visit_cpus mask. Guard this with cpu_count.

	 */

	cpu_count = cpumask_weight(&visit_cpus);



	while (!cpumask_empty(&visit_cpus)) {

		struct sched_group *sg_shared_cap = NULL;
@@ -6261,8 +6251,6 @@ static int compute_energy(struct energy_env *eenv) 
		/*

		 * Is the group utilization affected by cpus outside this

		 * sched_group?

		 * This sd may have groups with cpus which were not present

		 * when we took visit_cpus.

		 */

		sd = rcu_dereference(per_cpu(sd_scs, cpu));

		if (sd && sd->parent)
@@ -6288,24 +6276,8 @@ static int compute_energy(struct energy_env *eenv) 
				calc_sg_energy(eenv);



				/* remove CPUs we have just visited */

				if (!sd->child) {

					/*

					 * cpu_count here is the number of

					 * cpus we expect to visit in this

					 * calculation. If we race against

					 * hotplug, we can have extra cpus

					 * added to the groups we are

					 * iterating which do not appear in

					 * the visit_cpus mask. In that case

					 * we are not able to calculate energy

					 * without restarting so we will bail

					 * out and use prev_cpu this time.

					 */

					if (!cpu_count)

						return -EINVAL;

				if (!sd->child)

					cpumask_xor(&visit_cpus, &visit_cpus, sched_group_span(sg));

					cpu_count--;

				}



				if (cpumask_equal(sched_group_span(sg), sched_group_span(eenv->sg_top)))

					goto next_cpu;