linux-kernel - [PATCH 3/3] cpufreq: Drop unnecessary cpus locking from store()

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Date:   Thu, 26 May 2022 17:21:21 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>
Cc:     linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 3/3] cpufreq: Drop unnecessary cpus locking from store()

This change was introduced long back by:

commit 4f750c930822 ("cpufreq: Synchronize the cpufreq store_*() routines with CPU hotplug")

Since then, both cpufreq and hotplug core have been reworked and have
much better locking in place. The race mentioned in commit 4f750c930822
isn't possible anymore.

Drop the unnecessary locking.

Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
---
 drivers/cpufreq/cpufreq.c | 19 ++++---------------
 1 file changed, 4 insertions(+), 15 deletions(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 53d163a84e06..bb237d1ce5e7 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -973,21 +973,10 @@ static ssize_t store(struct kobject *kobj, struct attribute *attr,
 	if (!fattr->store)
 		return -EIO;
 
-	/*
-	 * cpus_read_trylock() is used here to work around a circular lock
-	 * dependency problem with respect to the cpufreq_register_driver().
-	 */
-	if (!cpus_read_trylock())
-		return -EBUSY;
-
-	if (cpu_online(policy->cpu)) {
-		down_write(&policy->rwsem);
-		if (likely(!policy_is_inactive(policy)))
-			ret = fattr->store(policy, buf, count);
-		up_write(&policy->rwsem);
-	}
-
-	cpus_read_unlock();
+	down_write(&policy->rwsem);
+	if (likely(!policy_is_inactive(policy)))
+		ret = fattr->store(policy, buf, count);
+	up_write(&policy->rwsem);
 
 	return ret;
 }
-- 
2.31.1.272.g89b43f80a514