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

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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: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Christian Loehle <christian.loehle@arm.com>
Tested-by: Christian Loehle <christian.loehle@arm.com>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://patch.msgid.link/2317800.iZASKD2KPV@rjwysocki.net
This commit is contained in:
Rafael J. Wysocki 2025-05-06 22:37:15 +02:00
parent f42c8556a0
commit 4854649b1f
3 changed files with 39 additions and 20 deletions
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32
drivers/cpufreq/cpufreq.c
View File

@ -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);

2
include/linux/cpufreq.h
View File

@ -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),

25
kernel/sched/topology.c
View File

@ -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. */
@ -248,25 +246,12 @@ 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 (sched_debug()) {
pr_info("rd %*pbl: Checking EAS, schedutil is mandatory\n",
cpumask_pr_args(cpu_mask));
}
return false;
if (!cpufreq_ready_for_eas(cpu_mask)) {
if (sched_debug()) {
pr_info("rd %*pbl: Checking EAS: cpufreq is not ready\n",
cpumask_pr_args(cpu_mask));
}
return false;
}
return true;