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In-Reply-To: <33720e72-a438-8ffe-1b5f-38756738ad9b@ti.com>
From:   Arnd Bergmann <arnd@kernel.org>
Date:   Fri, 12 Feb 2021 21:23:23 +0100
Message-ID: <CAK8P3a0JEhhw4vB=YgUJj5_ywds=sVuzPd4Zf0iiRwX4Mgsk3g@mail.gmail.com>
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()
To:     Grygorii Strashko <grygorii.strashko@ti.com>
Cc:     "Song Bao Hua (Barry Song)" <song.bao.hua@hisilicon.com>,
        Andy Shevchenko <andy.shevchenko@gmail.com>,
        luojiaxing <luojiaxing@huawei.com>,
        Linus Walleij <linus.walleij@linaro.org>,
        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" <linuxarm@openeuler.org>
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On Fri, Feb 12, 2021 at 12:53 PM Grygorii Strashko
<grygorii.strashko@ti.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