[PATCH] arm64: Utilize for_each_cpu_wrap for reference lookup

Beata Michalska
2025-02-18T19:24:41Z

While searching for a reference CPU within a given policy,
arch_freq_get_on_cpu relies on cpumask_next_wrap to iterate over
all available CPUs and to ensure each is verified only once.
Recent changes to cpumask_next_wrap will handle the latter no more,
so switching to for_each_cpu_wrap, which preserves expected behavior
while ensuring compatibility with the updates.

Fixes: 16d1e27475f6 ("arm64: Provide an AMU-based version of arch_freq_get_on_cpu")
Signed-off-by: Beata Michalska <beata.michalska@arm.com>
---
based on arm64 for-next/amuv1-avg-freq

arch/arm64/kernel/topology.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
index a09b0551ec59..9e3583720668 100644
--- a/arch/arm64/kernel/topology.c
+++ b/arch/arm64/kernel/topology.c
@@ -254,7 +254,7 @@ int arch_freq_get_on_cpu(int cpu)
if (!housekeeping_cpu(cpu, HK_TYPE_TICK) ||
time_is_before_jiffies(last_update + msecs_to_jiffies(AMU_SAMPLE_EXP_MS))) {
struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
- int ref_cpu = cpu;
+ int ref_cpu;

if (!policy)
return -EINVAL;
@@ -265,11 +265,15 @@ int arch_freq_get_on_cpu(int cpu)
return -EOPNOTSUPP;
}

- do {
- ref_cpu = cpumask_next_wrap(ref_cpu, policy->cpus,
- start_cpu, true);
-
- } while (ref_cpu < nr_cpu_ids && idle_cpu(ref_cpu));
+ for_each_cpu_wrap(ref_cpu, policy->cpus, cpu + 1) {
+ if (ref_cpu == start_cpu) {
+ /* Prevent verifying same CPU twice */
+ ref_cpu = nr_cpu_ids;
+ break;
+ }
+ if (!idle_cpu(ref_cpu))
+ break;
+ }

cpufreq_cpu_put(policy);

--
2.25.1