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Commit 9c7d644f authored by Puja Gupta's avatar Puja Gupta
Browse files

sched: Don't update idle_cpus_mask during core isolation 



Remove code to update nohz.idle_cpus_mask from
do_isolation_work_cpu_stop(), instead update find_new_ilb() to exclude
isolated_cpus. This is done to fix the issue where cpu is not present
in nohz.idle_cpus_mask but NOHZ_TICK_STOPPED is set. As a result even
if the cpu is unisolated, task won't see the cpu as idle due to
inconsistent nohz.idle_cpus_mask.
Also restore nohz_balance_exit_idle() to upstream version.

Change-Id: I126d256446fee541284a39d16c2a7739c2d30414
Signed-off-by: default avatarPuja Gupta <pujag@codeaurora.org>
parent d98d9ee8

kernel/sched/core.c

+0 −6
Original line number Diff line number Diff line
@@ -5956,12 +5956,6 @@ int do_isolation_work_cpu_stop(void *data) 
		set_rq_online(rq);

	raw_spin_unlock(&rq->lock);



	/*

	 * We might have been in tickless state. Clear NOHZ flags to avoid

	 * us being kicked for helping out with balancing

	 */

	nohz_balance_clear_nohz_mask(cpu);



	clear_walt_request(cpu);

	local_irq_enable();

	return 0;

kernel/sched/fair.c

+22 −14
Original line number Diff line number Diff line
@@ -9900,6 +9900,8 @@ static inline int find_new_ilb(int type) 
	if (sd) {

		cpumask_and(&cpumask, nohz.idle_cpus_mask,

			    sched_domain_span(sd));

		cpumask_andnot(&cpumask, &cpumask,

			    cpu_isolated_mask);

		ilb = cpumask_first(&cpumask);

	}

	rcu_read_unlock();
@@ -9908,8 +9910,11 @@ static inline int find_new_ilb(int type) 
		if (!energy_aware() ||

		    (capacity_orig_of(cpu) ==

		     cpu_rq(cpu)->rd->max_cpu_capacity.val ||

		     cpu_overutilized(cpu)))

			ilb = cpumask_first(nohz.idle_cpus_mask);

		     cpu_overutilized(cpu))) {

			cpumask_andnot(&cpumask, nohz.idle_cpus_mask,

			    cpu_isolated_mask);

			ilb = cpumask_first(&cpumask);

		}

	}



	if (ilb < nr_cpu_ids && idle_cpu(ilb))
@@ -9946,21 +9951,16 @@ static void nohz_balancer_kick(int type) 
	return;

}



void nohz_balance_clear_nohz_mask(int cpu)

{

	if (likely(cpumask_test_cpu(cpu, nohz.idle_cpus_mask))) {

		cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);

		atomic_dec(&nohz.nr_cpus);

	}

}



void nohz_balance_exit_idle(unsigned int cpu)

{

	if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {

		/*

		 * Completely isolated CPUs don't ever set, so we must test.

		 */

		nohz_balance_clear_nohz_mask(cpu);

		if (likely(cpumask_test_cpu(cpu, nohz.idle_cpus_mask))) {

			cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);

			atomic_dec(&nohz.nr_cpus);

		}

		clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));

	}

}
@@ -10235,6 +10235,7 @@ static inline bool nohz_kick_needed(struct rq *rq, int *type) 
	int nr_busy;

	int cpu = rq->cpu;

	bool kick = false;

	cpumask_t cpumask;



	if (unlikely(rq->idle_balance))

		return false;
@@ -10250,7 +10251,8 @@ static inline bool nohz_kick_needed(struct rq *rq, int *type) 
	 * None are in tickless mode and hence no need for NOHZ idle load

	 * balancing.

	 */

	if (likely(!atomic_read(&nohz.nr_cpus)))

	cpumask_andnot(&cpumask, nohz.idle_cpus_mask, cpu_isolated_mask);

	if (cpumask_empty(&cpumask))

		return false;



	if (time_before(now, nohz.next_balance))
@@ -10284,8 +10286,7 @@ static inline bool nohz_kick_needed(struct rq *rq, int *type) 
	}



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

	if (sd && (cpumask_first_and(nohz.idle_cpus_mask,

				  sched_domain_span(sd)) < cpu)) {

	if (sd && (cpumask_first_and(&cpumask, sched_domain_span(sd)) < cpu)) {

		kick = true;

		goto unlock;

	}
@@ -10308,6 +10309,13 @@ static __latent_entropy void run_rebalance_domains(struct softirq_action *h) 
	enum cpu_idle_type idle = this_rq->idle_balance ?

						CPU_IDLE : CPU_NOT_IDLE;



	/*

	 * Since core isolation doesn't update nohz.idle_cpus_mask, there

	 * is a possibility this nohz kicked cpu could be isolated. Hence

	 * return if the cpu is isolated.

	 */

	if (cpu_isolated(this_rq->cpu))

		return;

	/*

	 * If this cpu has a pending nohz_balance_kick, then do the

	 * balancing on behalf of the other idle cpus whose ticks are

kernel/sched/sched.h

+0 −1
Original line number Diff line number Diff line
@@ -1444,7 +1444,6 @@ extern void init_max_cpu_capacity(struct max_cpu_capacity *mcc); 
extern void update_group_capacity(struct sched_domain *sd, int cpu);



extern void trigger_load_balance(struct rq *rq);

extern void nohz_balance_clear_nohz_mask(int cpu);



extern void set_cpus_allowed_common(struct task_struct *p, const struct cpumask *new_mask);