linux-kernel - Re: [PATCH] Revert "gpio: mpc8xxx: change the gpio interrupt flags."

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Message-ID: <CAMpxmJWrmVNb2jYs8e585kDnE+Xv8yNiFpABh3RwDUFg1KAWqA@mail.gmail.com>
Date:   Sun, 18 Jul 2021 14:53:09 +0200
From:   Bartosz Golaszewski <bgolaszewski@...libre.com>
To:     Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Song Hui <hui.song_1@....com>,
        "Stable # 4 . 20+" <stable@...r.kernel.org>,
        linux-gpio <linux-gpio@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Revert "gpio: mpc8xxx: change the gpio interrupt flags."

On Fri, Jul 2, 2021 at 3:37 PM Rasmus Villemoes
<linux@...musvillemoes.dk> wrote:
>
> This reverts commit 3d5bfbd9716318b1ca5c38488aa69f64d38a9aa5.
>
> When booting with threadirqs, it causes a splat
>
>   WARNING: CPU: 0 PID: 29 at kernel/irq/handle.c:159 __handle_irq_event_percpu+0x1ec/0x27c
>   irq 66 handler irq_default_primary_handler+0x0/0x1c enabled interrupts
>
> That splat later went away with commit 81e2073c175b ("genirq: Disable
> interrupts for force threaded handlers"), which got backported to
> -stable. However, when running an -rt kernel, the splat still
> exists. Moreover, quoting Thomas Gleixner [1]
>
>   But 3d5bfbd97163 ("gpio: mpc8xxx: change the gpio interrupt flags.")
>   has nothing to do with that:
>
>       "Delete the interrupt IRQF_NO_THREAD flags in order to gpio interrupts
>        can be threaded to allow high-priority processes to preempt."
>
>   This changelog is blatantly wrong. In mainline forced irq threads
>   have always been invoked with softirqs disabled, which obviously
>   makes them non-preemptible.
>
> So the patch didn't even do what its commit log said.
>
> [1] https://lore.kernel.org/lkml/871r8zey88.ffs@nanos.tec.linutronix.de/
>
> Cc: stable@...r.kernel.org # v5.9+
> Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
> ---

Applied for fixes, thanks!

Bartosz