linux-kernel - [PATCH] Revert "cpufreq: Fix possible race in cpufreq online error path"

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Message-Id: <7f505491f4e8207bb5d79b1b7b34a28b6d1f03b6.1652068655.git.viresh.kumar@linaro.org>
Date:   Mon,  9 May 2022 09:27:37 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Rafael Wysocki <rjw@...ysocki.net>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Schspa Shi <schspa@...il.com>
Cc:     linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] Revert "cpufreq: Fix possible race in cpufreq online error path"

This reverts commit f346e96267cd76175d6c201b40f770c0116a8a04.

The commit tried to fix a possible real bug but it made it even worse.
The fix was simply buggy as now an error out to out_offline_policy or
out_exit_policy will try to release a semaphore which was never taken in
the first place. This works fine only if we failed late, i.e. via
out_destroy_policy.

Fixes: f346e96267cd ("cpufreq: Fix possible race in cpufreq online error path")
Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
---
 drivers/cpufreq/cpufreq.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 233e8af48848..fbaa8e6c7d23 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1534,6 +1534,8 @@ static int cpufreq_online(unsigned int cpu)
 	for_each_cpu(j, policy->real_cpus)
 		remove_cpu_dev_symlink(policy, get_cpu_device(j));
 
+	up_write(&policy->rwsem);
+
 out_offline_policy:
 	if (cpufreq_driver->offline)
 		cpufreq_driver->offline(policy);
@@ -1542,9 +1544,6 @@ static int cpufreq_online(unsigned int cpu)
 	if (cpufreq_driver->exit)
 		cpufreq_driver->exit(policy);
 
-	cpumask_clear(policy->cpus);
-	up_write(&policy->rwsem);
-
 out_free_policy:
 	cpufreq_policy_free(policy);
 	return ret;
-- 
2.31.1.272.g89b43f80a514