lkml.org 
[lkml]   [2020]   [Mar]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] gpiolib: don't call sleeping functions with a spinlock taken
Date
From: Bartosz Golaszewski <bgolaszewski@baylibre.com>

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: d2ac25798208 ("gpiolib: provide a dedicated function for setting lineinfo")
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
---
drivers/gpio/gpiolib.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 02f8b2b81199..ee20634a522c 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1154,8 +1154,19 @@ static void gpio_desc_to_lineinfo(struct gpio_desc *desc,
struct gpioline_info *info)
{
struct gpio_chip *chip = 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(
+ chip->base + info->line_offset);
+
spin_lock_irqsave(&gpio_lock, flags);

if (desc->name) {
@@ -1182,7 +1193,7 @@ 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(chip->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;
--
2.25.0
\
 
 \ /
  Last update: 2020-03-20 10:32    [W:0.124 / U:1.776 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site