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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Message-ID: <CAK8P3a0JEhhw4vB=YgUJj5_ywds=sVuzPd4Zf0iiRwX4Mgsk3g@mail.gmail.com>
Date:   Fri, 12 Feb 2021 21:23:23 +0100
From:   Arnd Bergmann <arnd@...nel.org>
To:     Grygorii Strashko <grygorii.strashko@...com>
Cc:     "Song Bao Hua (Barry Song)" <song.bao.hua@...ilicon.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        luojiaxing <luojiaxing@...wei.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        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 12:53 PM Grygorii Strashko
<grygorii.strashko@...com> wrote:
>
> The worst RT case I can imagine is when gpio API is still called from hard IRQ context by some
> other device driver - some toggling for example.
> Note. RT or "threadirqs" does not mean gpiochip become sleepable.
>
> In this case:
>   threaded handler
>     raw_spin_lock
>         IRQ from other device
>            hard_irq handler
>              gpiod_x()
>                 raw_spin_lock_irqsave() -- oops
>

Good point, I had missed the fact that drivers can call gpio functions from
hardirq context when I replied earlier, gpio is clearly special here.

          Arnd