Commit da07d2f9 authored by Qais Yousef's avatar Qais Yousef Committed by Peter Zijlstra
Browse files

sched/fair: Fixes for capacity inversion detection 



Traversing the Perf Domains requires rcu_read_lock() to be held and is
conditional on sched_energy_enabled(). Ensure right protections applied.

Also skip capacity inversion detection for our own pd; which was an
error.

Fixes: 44c7b80b ("sched/fair: Detect capacity inversion")
Reported-by: default avatarDietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: default avatarQais Yousef (Google) <qyousef@layalina.io>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarVincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20230112122708.330667-3-qyousef@layalina.io
parent e26fd28d

kernel/sched/fair.c

+11 −2
Original line number Diff line number Diff line
@@ -8868,16 +8868,23 @@ static void update_cpu_capacity(struct sched_domain *sd, int cpu) 
	 *   * Thermal pressure will impact all cpus in this perf domain

	 *     equally.

	 */

	if (static_branch_unlikely(&sched_asym_cpucapacity)) {

	if (sched_energy_enabled()) {

		unsigned long inv_cap = capacity_orig - thermal_load_avg(rq);

		struct perf_domain *pd = rcu_dereference(rq->rd->pd);

		struct perf_domain *pd;



		rcu_read_lock();



		pd = rcu_dereference(rq->rd->pd);

		rq->cpu_capacity_inverted = 0;



		for (; pd; pd = pd->next) {

			struct cpumask *pd_span = perf_domain_span(pd);

			unsigned long pd_cap_orig, pd_cap;



			/* We can't be inverted against our own pd */

			if (cpumask_test_cpu(cpu_of(rq), pd_span))

				continue;



			cpu = cpumask_any(pd_span);

			pd_cap_orig = arch_scale_cpu_capacity(cpu);
@@ -8902,6 +8909,8 @@ static void update_cpu_capacity(struct sched_domain *sd, int cpu) 
				break;

			}

		}



		rcu_read_unlock();

	}



	trace_sched_cpu_capacity_tp(rq);