linux-kernel - [PATCH 1/1] cpufreq: Fix show()/store() issue for hotplugging offline CPU

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Date:   Wed, 19 Oct 2022 16:40:45 +0800
From:   'Guanjun' <guanjun@...ux.alibaba.com>
To:     schspa@...il.com, rafael@...nel.org, viresh.kumar@...aro.org
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        guanjun@...ux.alibaba.com, zelin.deng@...ux.alibaba.com
Subject: [PATCH 1/1] cpufreq: Fix show()/store() issue for hotplugging offline CPU

From: Zelin Deng <zelin.deng@...ux.alibaba.com>

After brought one CPU offline, lscpu returned failure:

lscpu: cannot read /sys/devices/system/cpu/cpu64/cpufreq/cpuinfo_max_freq: Device or resource busy

which had blocked all outputs of lscpu.

This is not the case mentioned in commit d4627a287e251, as the policy
had been created successfully but is inactive due to CPU gets offline.
To fix this issue, just add an addtional check whether CPU is online or
not.

Fixes: d4627a287e251 ("cpufreq: Abort show()/store() for half-initialized policies")
Signed-off-by: Zelin Deng <zelin.deng@...ux.alibaba.com>
Signed-off-by: Guanjun <guanjun@...ux.alibaba.com>
---
 drivers/cpufreq/cpufreq.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 69b3d61852ac..aa238ba7d2fe 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -956,8 +956,12 @@ static ssize_t show(struct kobject *kobj, struct attribute *attr, char *buf)
 		return -EIO;
 
 	down_read(&policy->rwsem);
-	if (likely(!policy_is_inactive(policy)))
-		ret = fattr->show(policy, buf);
+	if (unlikely(policy_is_inactive(policy) && cpu_online(policy->cpu)))
+		goto err;
+
+	ret = fattr->show(policy, buf);
+
+err:
 	up_read(&policy->rwsem);
 
 	return ret;
@@ -974,8 +978,12 @@ static ssize_t store(struct kobject *kobj, struct attribute *attr,
 		return -EIO;
 
 	down_write(&policy->rwsem);
-	if (likely(!policy_is_inactive(policy)))
-		ret = fattr->store(policy, buf, count);
+	if (unlikely(policy_is_inactive(policy) && cpu_online(policy->cpu)))
+		goto err;
+
+	ret = fattr->store(policy, buf, count);
+
+err:
 	up_write(&policy->rwsem);
 
 	return ret;
-- 
2.32.0.GIT