Re: [PATCH v2 19/23] gpio: sysfs: use per-gpio locking

From: Linus Walleij
Date: Tue May 12 2015 - 04:40:00 EST

On Mon, May 4, 2015 at 5:10 PM, Johan Hovold <johan@xxxxxxxxxx> wrote:

> Add a per-gpio mutex to serialise attribute operations rather than use
> one global mutex for all gpios and chips.
> Having a single global lock for all gpios in a system adds unnecessary
> latency to the sysfs interface, and especially when having gpio
> controllers connected over slow buses.
> Now that the global gpio-sysfs interrupt table is gone and with per-gpio
> data in place, we can easily switch to using a more fine-grained locking
> scheme.
> Keep the global mutex to serialise the global (class) operations of gpio
> export and unexport and chip removal.
> Also document the locking assumptions made.
> Note that this is also needed to fix a race between gpiod_export and
> gpiod_unexport.
> Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>

Patch applied.

Linus Walleij
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