linux-kernel - Re: [PATCH 2/4] pwm: Reduce time the pwm_lock mutex is held in pwmchip

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Date:   Thu, 17 Nov 2022 15:00:24 +0100
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     linux-pwm@...r.kernel.org,
        Thierry Reding <thierry.reding@...il.com>,
        linux-kernel@...r.kernel.org, kernel@...gutronix.de
Subject: Re: [PATCH 2/4] pwm: Reduce time the pwm_lock mutex is held in
 pwmchip_add()

Hello Andy,

On Wed, Nov 16, 2022 at 10:11:32AM +0200, Andy Shevchenko wrote:
> On Tue, Nov 15, 2022 at 10:15:13PM +0100, Uwe Kleine-König wrote:
> > This simplifies error handling as the need for goto error handling goes
> > away and at the end of the function the code can be simplified as this
> > code isn't used in the error case any more.
> 
> ...
> 
> > +	mutex_unlock(&pwm_lock);
> >  
> >  	if (IS_ENABLED(CONFIG_OF))
> >  		of_pwmchip_add(chip);
> 
> Why calling this without a lock is not a problem? Commit message doesn't share
> a bit about this change.

Maybe add another paragraph at the end reading:

Now memory allocation and the call to of_pwmchip_add() are done without
holding the lock. Both don't access the data structures protected by
&pwm_lock.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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