linux-kernel - [PATCH 2/3] cpufreq: Panic if policy is active in cpufreq_policy

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Message-Id: <8c3d50faf8811e86136fb3f9c459e43fc3c50bc0.1653565641.git.viresh.kumar@linaro.org>
Date:   Thu, 26 May 2022 17:21:20 +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 2/3] cpufreq: Panic if policy is active in cpufreq_policy_free()

With the new design in place, show/store callbacks check if the policy
is active or not before proceeding further and cpufreq_policy_free()
must be called after emptying policy->cpus mask, i.e. inactive policy.

Lets make sure we don't get a bug around this later and catch this early
by putting a BUG_ON() within cpufreq_policy_free().

Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
---
 drivers/cpufreq/cpufreq.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index e24aa5d4bca5..53d163a84e06 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1284,6 +1284,12 @@ static void cpufreq_policy_free(struct cpufreq_policy *policy)
 	unsigned long flags;
 	int cpu;
 
+	/*
+	 * The callers must ensure the policy is inactive by now, to avoid any
+	 * races with show()/store() callbacks.
+	 */
+	BUG_ON(!policy_is_inactive(policy));
+
 	/* Remove policy from list */
 	write_lock_irqsave(&cpufreq_driver_lock, flags);
 	list_del(&policy->policy_list);
-- 
2.31.1.272.g89b43f80a514