linux-kernel - Re: [PATCH] gpiolib: fix line event timestamps for nested irqs

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Date:   Fri, 11 Jan 2019 13:19:26 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Bartosz Golaszewski <brgl@...ev.pl>
Cc:     "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH] gpiolib: fix line event timestamps for nested irqs

On Fri, Jan 4, 2019 at 11:32 AM Bartosz Golaszewski <brgl@...ev.pl> wrote:

> From: Bartosz Golaszewski <bgolaszewski@...libre.com>
>
> Nested interrupts run inside the calling thread's context and the top
> half handler is never called which means that we never read the
> timestamp.
>
> This issue came up when trying to read line events from a gpiochip
> using regmap_irq_chip for interrupts.
>
> Fix it by reading the timestamp from the irq thread function if it's
> still 0 by the time the second handler is called.
>
> Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>

Oh that's right. Should this not have Fixes: and Cc: stable?

> +       /*
> +        * We may be running from a nested threaded interrupt in which case
> +        * we didn't get the timestamp from lineevent_irq_handler().
> +        */
> +       if (!le->timestamp)
> +               le->timestamp = ktime_get_real_ns();
> +
>         ge.timestamp = le->timestamp;

I would merge these:

if (!le->timestamp)
    ge.timestamp = ktime_get_real_ns();
else
    ge.timestamp = le->timestamp;

Yours,
Linus Walleij