Commit 4854649b authored by Rafael J. Wysocki's avatar Rafael J. Wysocki
Browse files

cpufreq/sched: Move cpufreq-specific EAS checks to cpufreq 



Doing cpufreq-specific EAS checks that require accessing policy
internals directly from sched_is_eas_possible() is a bit unfortunate,
so introduce cpufreq_ready_for_eas() in cpufreq, move those checks
into that new function and make sched_is_eas_possible() call it.

While at it, address a possible race between the EAS governor check
and governor change by doing the former under the policy rwsem.

Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: default avatarChristian Loehle <christian.loehle@arm.com>
Tested-by: default avatarChristian Loehle <christian.loehle@arm.com>
Reviewed-by: default avatarDietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://patch.msgid.link/2317800.iZASKD2KPV@rjwysocki.net
parent f42c8556

drivers/cpufreq/cpufreq.c

+32 −0
Original line number Diff line number Diff line
@@ -3056,6 +3056,38 @@ static int __init cpufreq_core_init(void) 


	return 0;

}



static bool cpufreq_policy_is_good_for_eas(unsigned int cpu)

{

	struct cpufreq_policy *policy __free(put_cpufreq_policy);



	policy = cpufreq_cpu_get(cpu);

	if (!policy) {

		pr_debug("cpufreq policy not set for CPU: %d\n", cpu);

		return false;

	}



	guard(cpufreq_policy_read)(policy);



	return sugov_is_governor(policy);

}



bool cpufreq_ready_for_eas(const struct cpumask *cpu_mask)

{

	unsigned int cpu;



	/* Do not attempt EAS if schedutil is not being used. */

	for_each_cpu(cpu, cpu_mask) {

		if (!cpufreq_policy_is_good_for_eas(cpu)) {

			pr_debug("rd %*pbl: schedutil is mandatory for EAS\n",

				 cpumask_pr_args(cpu_mask));

			return false;

		}

	}



	return true;

}



module_param(off, int, 0444);

module_param_string(default_governor, default_governor, CPUFREQ_NAME_LEN, 0444);

core_initcall(cpufreq_core_init);

include/linux/cpufreq.h

+2 −0
Original line number Diff line number Diff line
@@ -1237,6 +1237,8 @@ void cpufreq_generic_init(struct cpufreq_policy *policy, 
		struct cpufreq_frequency_table *table,

		unsigned int transition_latency);



bool cpufreq_ready_for_eas(const struct cpumask *cpu_mask);



static inline void cpufreq_register_em_with_opp(struct cpufreq_policy *policy)

{

	dev_pm_opp_of_register_em(get_cpu_device(policy->cpu),

kernel/sched/topology.c

+5 −20
Original line number Diff line number Diff line
@@ -212,8 +212,6 @@ static bool sched_energy_update; 
static bool sched_is_eas_possible(const struct cpumask *cpu_mask)

{

	bool any_asym_capacity = false;

	struct cpufreq_policy *policy;

	bool policy_is_ready;

	int i;



	/* EAS is enabled for asymmetric CPU capacity topologies. */
@@ -248,26 +246,13 @@ static bool sched_is_eas_possible(const struct cpumask *cpu_mask) 
		return false;

	}



	/* Do not attempt EAS if schedutil is not being used. */

	for_each_cpu(i, cpu_mask) {

		policy = cpufreq_cpu_get(i);

		if (!policy) {

			if (sched_debug()) {

				pr_info("rd %*pbl: Checking EAS, cpufreq policy not set for CPU: %d",

					cpumask_pr_args(cpu_mask), i);

			}

			return false;

		}

		policy_is_ready = sugov_is_governor(policy);

		cpufreq_cpu_put(policy);

		if (!policy_is_ready) {

	if (!cpufreq_ready_for_eas(cpu_mask)) {

		if (sched_debug()) {

				pr_info("rd %*pbl: Checking EAS, schedutil is mandatory\n",

			pr_info("rd %*pbl: Checking EAS: cpufreq is not ready\n",

				cpumask_pr_args(cpu_mask));

		}

		return false;

	}

	}



	return true;

}