linux-kernel - Re: [PATCH 11/13] timekeeping: remove xtime

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Date:   Mon, 12 Oct 2020 15:37:09 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Russell King <linux@...linux.org.uk>,
        Tony Luck <tony.luck@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Greg Ungerer <gerg@...ux-m68k.org>,
        Finn Thain <fthain@...egraphics.com.au>,
        Philip Blundell <philb@....org>,
        Joshua Thompson <funaho@...ai.org>,
        Sam Creasey <sammy@...my.net>,
        "James E.J. Bottomley" <James.Bottomley@...senpartnership.com>,
        Helge Deller <deller@....de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        John Stultz <john.stultz@...aro.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        "linux-ia64@...r.kernel.org" <linux-ia64@...r.kernel.org>,
        Parisc List <linux-parisc@...r.kernel.org>,
        linux-m68k <linux-m68k@...ts.linux-m68k.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 11/13] timekeeping: remove xtime_update

On Mon, Oct 12, 2020 at 3:16 PM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> On Thu, Oct 8, 2020 at 5:48 PM Arnd Bergmann <arnd@...db.de> wrote:
> > There are no more users of xtime_update aside from legacy_timer_tick(),
> > so fold it into that function and remove the declaration.
> >
> > update_process_times() is now only called inside of the kernel/time/
> > code, so the declaration can be moved there.
> >
> > Signed-off-by: Arnd Bergmann <arnd@...db.de>
>
> Thanks for your patch!
>
> Reviewed-by: Geert Uytterhoeven <geert@...ux-m68k.org>
>
> The comment about xtime_update() in arch/ia64/kernel/time.c needs
> an update.

I think the correct action for ia64 would be to make it a
proper clockevent driver with oneshot support, and remove
the rest of this logic.

I could try to rewrite the comment, but I tried not to touch that
part since I don't understand the logic behind it. Maybe the
ia64 maintainers can comment here why it even tries to skip
a timer tick. Is there a danger of ending up with the timer irq
permanently disabled if the timer_interrupt() function returns
with the itm register in the past, or is this simply about not having
too many interrupts in a row?

> Does the comment about update_process_times() in
> arch/openrisc/kernel/time.c needs an update, too?

I think that one is still technically correct.

       Arnd