linux-kernel - Re: [PATCH stable] tick/nohz: Prevent bogus softirq pending warning

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Message-ID: <CAMuHMdXyAQP_GYyHXJd7qq1ww25TbVs5QONDTqzLK_arGiLeMQ@mail.gmail.com>
Date:   Thu, 27 Sep 2018 10:07:39 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     John Crispin <john@...ozen.org>, frederic@...nel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Anna-Maria Gleixner <anna-maria@...utronix.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        stable <stable@...r.kernel.org>
Subject: Re: [PATCH stable] tick/nohz: Prevent bogus softirq pending warning

Hi Greg,

On Wed, Sep 12, 2018 at 3:56 PM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> On Thu, Aug 30, 2018 at 5:06 PM Thomas Gleixner <tglx@...utronix.de> wrote:
> > Commit 0a0e0829f990 ("nohz: Fix missing tick reprogram when interrupting an
> > inline softirq") got backported to stable trees and now causes the NOHZ
> > softirq pending warning to trigger. It's not an upstream issue as the NOHZ
> > update logic has been changed there.
> >
> > The problem is when a softirq disabled section gets interrupted and on
> > return from interrupt the tick/nohz state is evaluated, which then can
> > observe pending soft interrupts. These soft interrupts are legitimately
> > pending because they cannot be processed as long as soft interrupts are
> > disabled and the interrupted code will correctly process them when soft
> > interrupts are reenabled.
> >
> > Add a check for softirqs disabled to the pending check to prevent the
> > warning.
> >
> > Reported-by: Grygorii Strashko <grygorii.strashko@...com>
> > Reported-by: John Crispin <john@...ozen.org>
> > Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> > Tested-by: Grygorii Strashko <grygorii.strashko@...com>
> > Tested-by: John Crispin <john@...ozen.org>
> > Cc: Frederic Weisbecker <frederic@...nel.org>
> > Cc: Ingo Molnar <mingo@...nel.org>
> > Cc: Anna-Maria Gleixner <anna-maria@...utronix.de>
> > Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > Cc: stable@...r.kernel.org
>
> Fixes: 2d898915ccf4838c ("nohz: Fix missing tick reprogram when
> interrupting an inline softirq")
>
> Issue in v4.14.x bisected to the above commit, and fixed by your patch.
>
> Tested-by: Geert Uytterhoeven <geert+renesas@...der.be>

This issue is still present in v4.14.72. Can you please apply Thomas' fix?
Thanks!

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds