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Subject: Re: [PATCH] kcov: properly check if we are in an interrupt
To: Dmitry Vyukov <dvyukov@google.com>,
        Peter Zijlstra <peterz@infradead.org>
References: <1474642273-112248-1-git-send-email-andreyknvl@google.com>
 <20160926163226.35cc76eb1a06083440cbb86d@linux-foundation.org>
 <CACT4Y+ZdxBwExjgxWqF8EwYR9AsmcVo-z7TypjiG9MMHedPSsw@mail.gmail.com>
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Cc: Andrew Morton <akpm@linux-foundation.org>,
        Andrey Konovalov <andreyknvl@google.com>,
        Nicolai Stange <nicstange@gmail.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Kees Cook <keescook@chromium.org>, James Morse <james.morse@arm.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Quentin Casasnovas <quentin.casasnovas@oracle.com>,
        Andrey Ryabinin <ryabinin.a.a@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>
From: Vegard Nossum <vegard.nossum@oracle.com>
Message-ID: <f05baa70-5a6f-c53f-89a6-a3279df6eb83@oracle.com>
Date: Tue, 27 Sep 2016 13:22:30 +0200
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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