linux-kernel - Re: [PATCH] kcov: properly check if we are in an interrupt

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Message-ID: <f05baa70-5a6f-c53f-89a6-a3279df6eb83@oracle.com>
Date:   Tue, 27 Sep 2016 13:22:30 +0200
From:   Vegard Nossum <vegard.nossum@...cle.com>
To:     Dmitry Vyukov <dvyukov@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Nicolai Stange <nicstange@...il.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Kees Cook <keescook@...omium.org>,
        James Morse <james.morse@....com>,
        LKML <linux-kernel@...r.kernel.org>,
        Quentin Casasnovas <quentin.casasnovas@...cle.com>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH] kcov: properly check if we are in an interrupt

On 09/27/2016 01:20 PM, Vegard Nossum wrote:
> Your patch was:
>
> -    if (!t || in_interrupt())
> +    if (!t || (preempt_count() & (HARDIRQ_MASK | SOFTIRQ_OFFSET
> +                            | NMI_MASK)))
>
> But look at the definitions:
>
> #define irq_count()     (preempt_count() & (HARDIRQ_MASK | SOFTIRQ_MASK \
>                                  | NMI_MASK))
> #define in_interrupt()          (irq_count())
>
> So isn't the patch a no-op to start with?

Eh, SOFTIRQ_OFFSET vs SOFTIRQ_MASK.

I'll just go stand in the corner.


Vegard