linux-kernel - [patch] cpufreq: ondemand: Use cpumask_var

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Date:   Fri, 22 Jul 2022 10:50:24 +0800
From:   Zhao Liu <zhao1.liu@...ux.intel.com>
To:     "Rafael J . Wysocki" <rafael@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        trivial@...nel.org, Rusty Russell <rusty@...tcorp.com.au>,
        Zhenyu Wang <zhenyuw@...ux.intel.com>,
        Zhao Liu <zhao1.liu@...el.com>,
        Zhao Liu <zhao1.liu@...ux.intel.com>
Subject: [patch] cpufreq: ondemand: Use cpumask_var_t for on-stack cpu mask

A cpumask structure on the stack can cause a warning with
CONFIG_NR_CPUS=8192 (e.g. Ubuntu 22.04 uses this):

drivers/cpufreq/cpufreq_ondemand.c: In function 'od_set_powersave_bias':
drivers/cpufreq/cpufreq_ondemand.c:449:1: warning: the frame size of
	1032 bytes is larger than 1024 bytes [-Wframe-larger-than=]
  449 | }
      | ^

CONFIG_CPUMASK_OFFSTACK=y is enabled by default for most distros, and
hence we can work around the warning by using cpumask_var_t.

Signed-off-by: Zhao Liu <zhao1.liu@...ux.intel.com>
---
 drivers/cpufreq/cpufreq_ondemand.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
index e8fbf970ff07..c52d19d67557 100644
--- a/drivers/cpufreq/cpufreq_ondemand.c
+++ b/drivers/cpufreq/cpufreq_ondemand.c
@@ -416,10 +416,13 @@ static struct dbs_governor od_dbs_gov = {
 static void od_set_powersave_bias(unsigned int powersave_bias)
 {
 	unsigned int cpu;
-	cpumask_t done;
+	cpumask_var_t done;
+
+	if (!alloc_cpumask_var(&done, GFP_KERNEL))
+		return;
 
 	default_powersave_bias = powersave_bias;
-	cpumask_clear(&done);
+	cpumask_clear(done);
 
 	cpus_read_lock();
 	for_each_online_cpu(cpu) {
@@ -428,7 +431,7 @@ static void od_set_powersave_bias(unsigned int powersave_bias)
 		struct dbs_data *dbs_data;
 		struct od_dbs_tuners *od_tuners;
 
-		if (cpumask_test_cpu(cpu, &done))
+		if (cpumask_test_cpu(cpu, done))
 			continue;
 
 		policy = cpufreq_cpu_get_raw(cpu);
@@ -439,13 +442,15 @@ static void od_set_powersave_bias(unsigned int powersave_bias)
 		if (!policy_dbs)
 			continue;
 
-		cpumask_or(&done, &done, policy->cpus);
+		cpumask_or(done, done, policy->cpus);
 
 		dbs_data = policy_dbs->dbs_data;
 		od_tuners = dbs_data->tuners;
 		od_tuners->powersave_bias = default_powersave_bias;
 	}
 	cpus_read_unlock();
+
+	free_cpumask_var(done);
 }
 
 void od_register_powersave_bias_handler(unsigned int (*f)
-- 
2.34.1