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gpiolib: don't call sleeping functions with a spinlock taken 

We must not call pinctrl_gpio_can_use_line() with the gpio_lock taken
as it takes a mutex internally. Let's move the call before taking the
spinlock and store the return value.

This isn't perfect - there's a moment between calling
pinctrl_gpio_can_use_line() and taking the spinlock where the situation
can change but it isn't a regression either: previously this part wasn't
protected at all and it only affects the information user-space is
seeing.

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Fixes: d2ac257982 ("gpiolib: provide a dedicated function for setting lineinfo")
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
This commit is contained in:
Bartosz Golaszewski 2020-04-17 09:01:51 +02:00
parent 4e15415930
commit 6409d049ce
1 changed files with 12 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
drivers/gpio/gpiolib.c
View File

@ -1158,8 +1158,19 @@ static void gpio_desc_to_lineinfo(struct gpio_desc *desc,
struct gpioline_info *info)
{
struct gpio_chip *gc = desc->gdev->chip;
bool ok_for_pinctrl;
unsigned long flags;
/*
* This function takes a mutex so we must check this before taking
* the spinlock.
*
* FIXME: find a non-racy way to retrieve this information. Maybe a
* lock common to both frameworks?
*/
ok_for_pinctrl =
pinctrl_gpio_can_use_line(gc->base + info->line_offset);
spin_lock_irqsave(&gpio_lock, flags);
if (desc->name) {
@ -1186,7 +1197,7 @@ static void gpio_desc_to_lineinfo(struct gpio_desc *desc,
test_bit(FLAG_USED_AS_IRQ, &desc->flags) ||
test_bit(FLAG_EXPORT, &desc->flags) ||
test_bit(FLAG_SYSFS, &desc->flags) ||
!pinctrl_gpio_can_use_line(gc->base + info->line_offset))
!ok_for_pinctrl)
info->flags |= GPIOLINE_FLAG_KERNEL;
if (test_bit(FLAG_IS_OUT, &desc->flags))
info->flags |= GPIOLINE_FLAG_IS_OUT;