linux-kernel - Re: [PATCH 3/4] gpiolib: cdev: reduce locking in gpio_desc_to

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Message-ID: <ZXm4C7KVkMwL4_sX@smile.fi.intel.com>
Date:   Wed, 13 Dec 2023 15:56:27 +0200
From:   Andy Shevchenko <andy@...nel.org>
To:     Kent Gibson <warthog618@...il.com>
Cc:     linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
        brgl@...ev.pl, linus.walleij@...aro.org
Subject: Re: [PATCH 3/4] gpiolib: cdev: reduce locking in
 gpio_desc_to_lineinfo()

On Tue, Dec 12, 2023 at 01:42:52PM +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 availabilty of the line from pinctrl if other checks
> pass, so avoiding the check for lines that are otherwise in use.

...

> -	bool ok_for_pinctrl;
> -	unsigned long flags;
> +	unsigned long iflags, dflags;

With a preliminary conversion to cleanup.h this whole change becomes cleaner,
no?

-- 
With Best Regards,
Andy Shevchenko