linux-kernel - Re: [PATCH] cpufreq: mediatek: Fix potential deadlock problem in mtk_cpufreq_set

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Message-ID: <61a4b23f-9740-6fb4-abd0-640d3353e788@vivo.com>
Date:   Tue, 10 May 2022 16:26:02 +0800
From:   Jiabing Wan <wanjiabing@...o.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Rex-BC Chen <rex-bc.chen@...iatek.com>,
        "Andrew-sh.Cheng" <andrew-sh.cheng@...iatek.com>,
        Jia-Wei Chang <jia-wei.chang@...iatek.com>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH] cpufreq: mediatek: Fix potential deadlock problem in
 mtk_cpufreq_set_target

Hi, Viresh Kumar

On 2022/5/10 16:12, Viresh Kumar wrote:
> On 10-05-22, 16:01, Wan Jiabing wrote:
>> Fix following coccichek error:
>> ./drivers/cpufreq/mediatek-cpufreq.c:199:2-8: preceding lock on line
>> ./drivers/cpufreq/mediatek-cpufreq.c:208:2-8: preceding lock on line
>>
>> mutex_lock is acquired but not released before return.
>> Use 'goto out' to help releasing the mutex_lock.
>>
>> Fixes: c210063b40ac ("cupful: mediatek: Add opp notification support")
> cupful ??

Sorry for the typo...

By the way, is this patch correct?

I am not sure whether it should return with the mutex_lock.
But IMO, it should release the lock before return.

If correct, I'll fix this typo in v2.

Thanks,

Wan Jiabing
>> Signed-off-by: Wan Jiabing <wanjiabing@...o.com>
>> ---
>>   drivers/cpufreq/mediatek-cpufreq.c | 6 ++++--
>>   1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/cpufreq/mediatek-cpufreq.c b/drivers/cpufreq/mediatek-cpufreq.c
>> index 75bf21ddf61f..4c6d53c99d79 100644
>> --- a/drivers/cpufreq/mediatek-cpufreq.c
>> +++ b/drivers/cpufreq/mediatek-cpufreq.c
>> @@ -196,7 +196,8 @@ static int mtk_cpufreq_set_target(struct cpufreq_policy *policy,
>>   
>>   	if (pre_vproc < 0) {
>>   		dev_err(cpu_dev, "invalid Vproc value: %d\n", pre_vproc);
>> -		return pre_vproc;
>> +		ret = pre_vproc;
>> +		goto out;
>>   	}
>>   
>>   	freq_hz = freq_table[index].frequency * 1000;
>> @@ -205,7 +206,8 @@ static int mtk_cpufreq_set_target(struct cpufreq_policy *policy,
>>   	if (IS_ERR(opp)) {
>>   		dev_err(cpu_dev, "cpu%d: failed to find OPP for %ld\n",
>>   			policy->cpu, freq_hz);
>> -		return PTR_ERR(opp);
>> +		ret = PTR_ERR(opp);
>> +		goto out;
>>   	}
>>   	vproc = dev_pm_opp_get_voltage(opp);
>>   	dev_pm_opp_put(opp);
>> -- 
>> 2.35.1