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

[Geert Uytterhoeven]

Hi Thomas,

On Thu, Aug 30, 2018 at 5:06 PM Thomas Gleixner <tglx@xxxxxxxxxxxxx> 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@xxxxxx>
> Reported-by: John Crispin <john@xxxxxxxxxxx>
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Tested-by: Grygorii Strashko <grygorii.strashko@xxxxxx>
> Tested-by: John Crispin <john@xxxxxxxxxxx>
> Cc: Frederic Weisbecker <frederic@xxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: Anna-Maria Gleixner <anna-maria@xxxxxxxxxxxxx>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx

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@xxxxxxxxx>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

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