linux-kernel - Re: [Linuxarm] Re: [PATCH for next v1 1/2] gpio: omap: Replace raw_spin_lock_irqsave with raw_spin_lock in omap_gpio_irq

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Date:   Fri, 12 Feb 2021 10:45:12 +0100
From:   Arnd Bergmann <arnd@...nel.org>
To:     "Song Bao Hua (Barry Song)" <song.bao.hua@...ilicon.com>
Cc:     Grygorii Strashko <grygorii.strashko@...com>,
        luojiaxing <luojiaxing@...wei.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Santosh Shilimkar <ssantosh@...nel.org>,
        Kevin Hilman <khilman@...nel.org>,
        "open list:GPIO SUBSYSTEM <linux-gpio@...r.kernel.org>,
        linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linuxarm@...neuler.org" <linuxarm@...neuler.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@...ilicon.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.

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().

       Arnd