On Wed, Dec 1, 2021 at 10:40 AM Hans Verkuil <hverkuil@xxxxxxxxx> wrote:
> [ 1674.787685] ___might_sleep+0x148/0x180
> [ 1674.791572] __might_sleep+0x54/0x90
> [ 1674.795195] mutex_lock+0x28/0x80
> [ 1674.798556] pinctrl_get_device_gpio_range+0x3c/0x110
There is the error ^
> gpiod_set_value() is supposed to be usable from an atomic context, so this
> appears to be a bug. It's probably been there for quite a long time. I suspect
> OPEN_DRAIN isn't very common, and I think this might be the first time I tested
> this driver with this kernel config option set.
Nah has nothing to do with open drain :)
> Any suggestions?
pinctrl_get_device_gpio_range() needs to be modified to not take a mutex
because mutex:es can sleep.
static int pinctrl_get_device_gpio_range(unsigned gpio,
struct pinctrl_dev **outdev,
struct pinctrl_gpio_range **outrange)
{
struct pinctrl_dev *pctldev;
mutex_lock(&pinctrldev_list_mutex);
BLAM!
And this definitely needs to be called on this path so no way out
of that.
This mutex pinctrldev_list_mutex is there to protect from devices coming
and going as we look for devices with ranges on.
One way to solve it would be to simply replace it with a spinlock, maybe
that works? (Check the code carefully so there are no things like calls
into drivers that may fire interrupts etc...)
If it still need to be sleepable (mutex-ish) you need to convert it to
use RCU I think? (Which would be pretty cool anyway.)
Yours,
Linus Walleij
