Subject: [PATCH v2] arm64: Utilize for_each_cpu_wrap for reference lookup

From: Beata Michalska <[email-masked]>
Date: Thu, 20 Feb 2025 09:10:15 +0000

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.
Not to mention that when iterating over each CPU, using a dedicated
iterator is preferable to an open-coded loop.

Fixes: 16d1e27475f6 ("arm64: Provide an AMU-based version of arch_freq_get_on_cpu")
Signed-off-by: Beata Michalska <[email-masked]>
---
 v2:
 Updated commit message

 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