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Message-ID: <1406013463-19218-3-git-send-email-acourbot@nvidia.com> Date: Tue, 22 Jul 2014 16:17:40 +0900 From: Alexandre Courbot <acourbot@...dia.com> To: Linus Walleij <linus.walleij@...aro.org> CC: <linux-gpio@...r.kernel.org>, <linux-kernel@...r.kernel.org>, <gnurou@...il.com>, Alexandre Courbot <acourbot@...dia.com> Subject: [PATCH 2/5] gpio: simplify gpiochip_export() For some reason gpiochip_export() would invalidate all the descriptors of a chip if exporting it to sysfs failed. This does not appear as necessary. Remove that part of the code. While we are at it, add a note about the non-safety of temporarily releasing a spinlock in the middle of the loop that protects its iterator, and explain why this is done. Signed-off-by: Alexandre Courbot <acourbot@...dia.com> --- drivers/gpio/gpiolib-sysfs.c | 20 +++++++++----------- 1 file changed, 9 insertions(+), 11 deletions(-) diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c index 3516502059f2..f150aa288fa1 100644 --- a/drivers/gpio/gpiolib-sysfs.c +++ b/drivers/gpio/gpiolib-sysfs.c @@ -760,18 +760,8 @@ int gpiochip_export(struct gpio_chip *chip) chip->exported = (status == 0); mutex_unlock(&sysfs_lock); - if (status) { - unsigned long flags; - unsigned gpio; - - spin_lock_irqsave(&gpio_lock, flags); - gpio = 0; - while (gpio < chip->ngpio) - chip->desc[gpio++].chip = NULL; - spin_unlock_irqrestore(&gpio_lock, flags); - + if (status) chip_dbg(chip, "%s: status %d\n", __func__, status); - } return status; } @@ -817,6 +807,14 @@ static int __init gpiolib_sysfs_init(void) if (!chip || chip->exported) continue; + /* + * TODO we yield gpio_lock here because gpiochip_export() + * acquires a mutex. This is unsafe and needs to be fixed. + * + * Also it would be nice to use gpiochip_find() here so we + * can keep gpio_chips local to gpiolib.c, but the yield of + * gpio_lock prevents us from doing this. + */ spin_unlock_irqrestore(&gpio_lock, flags); status = gpiochip_export(chip); spin_lock_irqsave(&gpio_lock, flags); -- 2.0.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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