From: Maxim Kochetkov <fido_max@inbox.ru>
To: linux-gpio@vger.kernel.org
Cc: bgolaszewski@baylibre.com, linus.walleij@linaro.org
Subject: gpiolib gpio_chrdev_release duration is about 30 ms
Date: Fri, 17 Jul 2020 15:56:45 +0300 [thread overview]
Message-ID: <7eb11c0d-cd11-f873-c336-4ec955a7bdb3@inbox.ru> (raw)
Hi.
I'm using libgpiod in userspace.
I have 6 gpiochip's on my board.
gpiod_line_find takes about 300ms to find GPIO line.
gpiod_line_find calls gpiod_foreach_chip
then gpiod_chip_iter_next
then gpiod_chip_close then close(chip->fd)
then we are going to kernel gpiolib gpio_chrdev_release
then atomic_notifier_chain_unregister
then synchronize_rcu()
synchronize_rcu takes about 30 ms (6*30ms=280ms)
I tried to remove synchronize_rcu from atomic_notifier_chain_unregister
and gpiod_line_find takes about 2ms now.
next reply other threads:[~2020-07-17 12:56 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-17 12:56 Maxim Kochetkov [this message]
2020-07-17 13:37 ` gpiolib gpio_chrdev_release duration is about 30 ms Linus Walleij
2020-07-17 13:44 ` Maxim Kochetkov
2020-07-17 14:17 ` Maxim Kochetkov
2020-07-17 15:07 ` Andy Shevchenko
2020-07-18 4:25 ` Kent Gibson
2020-07-20 8:14 ` Maxim Kochetkov
2020-07-24 19:36 ` Bartosz Golaszewski
2020-07-25 3:52 ` Kent Gibson
2020-07-26 11:04 ` Bartosz Golaszewski
2020-07-26 22:32 ` Linus Walleij
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