linux-kernel - Re: [PATCH v3] platform/x86: Add support for improved performance mode

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Date:   Wed, 22 Nov 2023 11:44:53 -0800
From:   Breno Leitao <leitao@...ian.org>
To:     Mark Pearson <mpearson-lenovo@...ebb.ca>
Cc:     platform-driver-x86@...r.kernel.org, hdegoede@...hat.com,
        ilpo.jarvinen@...ux.intel.com,
        ibm-acpi-devel@...ts.sourceforge.net, mario.limonciello@....com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] platform/x86: Add support for improved performance
 mode

On Mon, Nov 13, 2023 at 11:54:33AM -0500, Mark Pearson wrote:
> @@ -10355,6 +10361,17 @@ static int dytc_profile_set(struct platform_profile_handler *pprof,
>  	if (err)
>  		goto unlock;
>  
> +	/* Set TMS mode appropriately (enable for performance), if available */
> +	if (dytc_ultraperf_cap) {
> +		int cmd;
> +
> +		cmd = DYTC_SET_COMMAND(DYTC_FUNCTION_TMS, DYTC_NOMODE,
> +				       profile == PLATFORM_PROFILE_PERFORMANCE);
> +		err = dytc_command(cmd, &output);
> +		if (err)
> +			return err;

Aren't you returning holding the 'dytc_mutex' mutex?

>From what I understand, in the first line of this function you get the lock,
and release later, at the exit, so, returning without releasing the lock might
be dangerous. Here is a summary of how I read this function with your change:


	mutex_lock_interruptible(&dytc_mutex);
	...
	err = dytc_command(cmd, &output);
	if (err)
		return err;

unlock:
	mutex_unlock(&dytc_mutex);
	return err;


I think "goto unlock" might solve it.