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)
2021-02-12T10:26:47Z

> -----Original Message-----
> From: Arnd Bergmann [mailto:arnd@kernel.org]
> Sent: Friday, February 12, 2021 10:45 PM
> To: Song Bao Hua (Barry Song) <song.bao.hua@hisilicon.com>
> Cc: Grygorii Strashko <grygorii.strashko@ti.com>; luojiaxing
> <luojiaxing@huawei.com>; Linus Walleij <linus.walleij@linaro.org>; Andy
> Shevchenko <andy.shevchenko@gmail.com>; Andy Shevchenko
> <andriy.shevchenko@linux.intel.com>; Santosh Shilimkar <ssantosh@kernel.org>;
> Kevin Hilman <khilman@kernel.org>; open list:GPIO SUBSYSTEM
> <linux-gpio@vger.kernel.org>, linux-kernel@vger.kernel.org
> <linux-kernel@vger.kernel.org>; linuxarm@openeuler.org
> Subject: 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()
>
> On Fri, Feb 12, 2021 at 6:05 AM Song Bao Hua (Barry Song)
> <song.bao.hua@hisilicon.com> wrote:
> > > -----Original Message-----
>
> > >
> > > 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.
>
> In a preempt-rt kernel, interrupts are run in task context, so they clearly
> should not be called with interrupts disabled, that would defeat the
> purpose of making them preemptible.

Yes. Sounds sensible. Irqsave in generic_handle_irq() will defeat
the purpose of RT.

>
> generic_handle_irq() does need to run with in_irq()==true though,
> but this should be set by the caller of the gpiochip's handler, and
> it is not set by raw_spin_lock_irqsave().
>

So sounds like this issue of in_irq()=true is still irrelevant with
this patch.

I guess this should have been set by the caller of the gpiochip's
handler somewhere, otherwise, gpiochip's irq handler won't be able
to be threaded. Has it been set somewhere?

> Arnd

Thanks
Barry