Re: [PATCH] gpio: omap: use raw locks for locking

[Linus Walleij <linus.walleij@linaro.org>]

On Tue, Jul 21, 2015 at 6:26 PM, Sebastian Andrzej Siewior
<bigeasy@linutronix.de> wrote:

> This patch converts gpio_bank.lock from a spin_lock into a
> raw_spin_lock. The call path is to access this lock is always under a
> raw_spin_lock, for instance
> - __setup_irq() holds &desc->lock with irq off
>   + __irq_set_trigger()
>    + omap_gpio_irq_type()
>
> - handle_level_irq() (runs with irqs off therefore raw locks)
>   + mask_ack_irq()
>    + omap_gpio_mask_irq()
>
> This fixes the obvious backtrace on -RT. However the locking vs context
> is not and this is not limited to -RT:
> - omap_gpio_irq_type() is called with IRQ off and has an conditional
>   call to pm_runtime_get_sync() which may sleep. Either it may happen or
>   it may not happen but pm_runtime_get_sync() should not be called with
>   irqs off.
>
> - omap_gpio_debounce() is holding the lock with IRQs off.
>   + omap2_set_gpio_debounce()
>    + clk_prepare_enable()
>     + clk_prepare() this one might sleep.
>   The number of users of gpiod_set_debounce() / gpio_set_debounce()
>   looks low but still this is not good.
>
> Acked-by: Javier Martinez Canillas <javier@dowhile0.org>
> Acked-by: Santosh Shilimkar <ssantosh@kernel.org>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Patch applied.

Now this question appear in my head:

Is drivers/gpio full of stuff that will not work with the -RT kernel,
and is this a change that should be done mutatis mutandis on
all the GPIO drivers?

Yours,
Linus Walleij