linux-kernel - Re: [PATCH RFT v2] gpio: cdev: use raw notifier for line state events

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Message-ID: <174185403526.7115.14841250128287935450.b4-ty@linaro.org>
Date: Thu, 13 Mar 2025 09:20:37 +0100
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Kent Gibson <warthog618@...il.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	David Jander <david@...tonic.nl>,
	Bartosz Golaszewski <brgl@...ev.pl>
Cc: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
	linux-gpio@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFT v2] gpio: cdev: use raw notifier for line state events

From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>


On Tue, 11 Mar 2025 15:31:43 +0100, Bartosz Golaszewski wrote:
> We use a notifier to implement the mechanism of informing the user-space
> about changes in GPIO line status. We register with the notifier when
> the GPIO character device file is opened and unregister when the last
> reference to the associated file descriptor is dropped.
> 
> Since commit fcc8b637c542 ("gpiolib: switch the line state notifier to
> atomic") we use the atomic notifier variant. Atomic notifiers call
> rcu_synchronize in atomic_notifier_chain_unregister() which caused a
> significant performance regression in some circumstances, observed by
> user-space when calling close() on the GPIO device file descriptor.
> 
> [...]

Applied, thanks!

[1/1] gpio: cdev: use raw notifier for line state events
      commit: dcb73cbaaeb39c9fd00bf2e019f911725945e2fe

Best regards,
-- 
Bartosz Golaszewski <bartosz.golaszewski@...aro.org>