linux-kernel - Re: [PATCH] cpufreq/amd-pstate: Remove unnecessary driver_lock in set

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Message-ID: <f10aab50-5d82-489b-8543-76301bf22e70@amd.com>
Date: Mon, 3 Feb 2025 09:34:32 -0600
From: Mario Limonciello <mario.limonciello@....com>
To: Viresh Kumar <viresh.kumar@...aro.org>,
 Dhananjay Ugwekar <dhananjay.ugwekar@....com>
Cc: gautham.shenoy@....com, rafael@...nel.org, linux-kernel@...r.kernel.org,
 linux-pm@...r.kernel.org
Subject: Re: [PATCH] cpufreq/amd-pstate: Remove unnecessary driver_lock in
 set_boost

On 2/3/2025 04:48, Viresh Kumar wrote:
> On 30-01-25, 08:52, Dhananjay Ugwekar wrote:
>> set_boost is a per-policy function call, hence a driver wide lock is
>> unnecessary. Also this mutex_acquire can collide with the mutex_acquire
>> from the mode-switch path in status_store(), which can lead to a
>> deadlock. So, remove it.
>>
>> Signed-off-by: Dhananjay Ugwekar <dhananjay.ugwekar@....com>
>> ---
>> PS: This patch should ideally go before [1], as that patch uncovers this
>> bug and actually leads to a deadlock when switching the amd_pstate driver
>> mode.
>> [1] https://lore.kernel.org/linux-pm/e16c06d4b8ffdb20e802ffe648f14dc515e60426.1737707712.git.viresh.kumar@linaro.org/
>> ---
>>   drivers/cpufreq/amd-pstate.c | 1 -
>>   1 file changed, 1 deletion(-)
>>
>> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
>> index d5be51bf8692..93788bce7e6a 100644
>> --- a/drivers/cpufreq/amd-pstate.c
>> +++ b/drivers/cpufreq/amd-pstate.c
>> @@ -740,7 +740,6 @@ static int amd_pstate_set_boost(struct cpufreq_policy *policy, int state)
>>   		pr_err("Boost mode is not supported by this processor or SBIOS\n");
>>   		return -EOPNOTSUPP;
>>   	}
>> -	guard(mutex)(&amd_pstate_driver_lock);
>>   
>>   	ret = amd_pstate_cpu_boost_update(policy, state);
>>   	refresh_frequency_limits(policy);
> 
> Applied. Thanks.
> 

Sorry for my delay with the recent holiday.
I have no concerns with this going to the start of the series.

Acked-by: Mario Limonciello <mario.limonciello@....com>