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

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Message-ID: <20250203104811.ccf3pj53cjlhwvti@vireshk-i7>
Date: Mon, 3 Feb 2025 16:18:11 +0530
From: Viresh Kumar <viresh.kumar@...aro.org>
To: Dhananjay Ugwekar <dhananjay.ugwekar@....com>
Cc: gautham.shenoy@....com, mario.limonciello@....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 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.

-- 
viresh