RE: [Linuxarm] Re: [PATCH for next v1 1/2] gpio: omap: Replace raw_spin_lock_irqsave with raw_spin_lock in omap_gpio_irq_handler()

[Song Bao Hua (Barry Song)]

> -----Original Message-----
> From: Grygorii Strashko [mailto:grygorii.strashko@xxxxxx]
> Sent: Friday, February 12, 2021 9:17 AM
> To: Arnd Bergmann <arnd@xxxxxxxxxx>
> Cc: luojiaxing <luojiaxing@xxxxxxxxxx>; Linus Walleij
> <linus.walleij@xxxxxxxxxx>; Andy Shevchenko <andy.shevchenko@xxxxxxxxx>; Andy
> Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>; Santosh Shilimkar
> <ssantosh@xxxxxxxxxx>; Kevin Hilman <khilman@xxxxxxxxxx>; open list:GPIO
> SUBSYSTEM <linux-gpio@xxxxxxxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx
> <linux-kernel@xxxxxxxxxxxxxxx>; linuxarm@xxxxxxxxxxxxx
> Subject: [Linuxarm] Re: [PATCH for next v1 1/2] gpio: omap: Replace
> raw_spin_lock_irqsave with raw_spin_lock in omap_gpio_irq_handler()
> 
> 
> 
> On 11/02/2021 21:39, Arnd Bergmann wrote:
> > On Thu, Feb 11, 2021 at 7:25 PM Grygorii Strashko
> > <grygorii.strashko@xxxxxx> wrote:
> >> On 08/02/2021 10:56, Luo Jiaxing wrote:
> >>> There is no need to use API with _irqsave in omap_gpio_irq_handler(),
> >>> because it already be in a irq-disabled context.
> >>
> >> NACK.
> >> Who said that this is always hard IRQ handler?
> >> What about RT-kernel or boot with "threadirqs"?
> >
> > In those cases, the interrupt handler is just a normal thread, so the
> > preempt_disable() that is implied by raw_spin_lock() is sufficient.
> >
> > Disabling interrupts inside of an interrupt handler is always incorrect,
> > the patch looks like a useful cleanup to me, if only for readability.
> 
> Note. there is also generic_handle_irq() call inside.

So generic_handle_irq() is not safe to run in thread thus requires
an interrupt-disabled environment to run? If so, I'd rather this
irqsave moved into generic_handle_irq() rather than asking everyone
calling it to do irqsave.

On the other hand, the author changed a couple of spin_lock_irqsave
to spin_lock, if only this one is incorrect, it seems it is worth a
new version to fix this.

> 
> --
> Best regards,
> grygorii

Thanks
Barry