linux-kernel - Re: [PATCH v3 3/5] gpiolib: cdev: reduce locking in gpio_desc_to

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Message-ID: <ZXzg2DkAPPQV8vft@rigel>
Date: Sat, 16 Dec 2023 07:27:20 +0800
From: Kent Gibson <warthog618@...il.com>
To: Andy Shevchenko <andy@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org, brgl@...ev.pl,
	linus.walleij@...aro.org
Subject: Re: [PATCH v3 3/5] gpiolib: cdev: reduce locking in
 gpio_desc_to_lineinfo()

On Fri, Dec 15, 2023 at 06:36:23PM +0200, Andy Shevchenko wrote:
> On Fri, Dec 15, 2023 at 10:38:03AM +0800, Kent Gibson wrote:
> > Reduce the time holding the gpio_lock by snapshotting the desc flags,
> > rather than testing them individually while holding the lock.
> >
> > Accept that the calculation of the used field is inherently racy, and
> > only check the availability of the line from pinctrl if other checks
> > pass, so avoiding the check for lines that are otherwise in use.
>
> Just wondering if you are using --histogram (diff algo) when preparing
> the patches...
>

Was just using the default myers.
Only changes patch 4, which it does make slightly more readable, so
will use it for v4.

Cheers,
Kent.