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

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Message-ID: <20160927105905.GI5016@twins.programming.kicks-ass.net>
Date:   Tue, 27 Sep 2016 12:59:05 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Dmitry Vyukov <dvyukov@...gle.com>
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>,
        Vegard Nossum <vegard.nossum@...cle.com>,
        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 Tue, Sep 27, 2016 at 09:50:41AM +0200, Dmitry Vyukov wrote:
> On Tue, Sep 27, 2016 at 9:34 AM, Peter Zijlstra <peterz@...radead.org> wrote:
> > On Tue, Sep 27, 2016 at 08:21:32AM +0200, Dmitry Vyukov wrote:
> >>
> >> I suspect there is a bunch of places that use in_interrupt(), but mean
> >> the same as KCOV wants -- am I in interrupt? and not am I in interrupt
> >> context or in normal task context but inside local_bh_disable(). For
> >> example, why does fput handles closure asynchronously if the task
> >> called local_bh_disable?
> >
> > Agreed, but it would mean auditing all in_interrupt()/irq_count() users.
> 
> 
> I don't think this means auditing all users. We are not making things
> worse by introduction of a new predicate.
> It would be nice to look at some uses in core code, but the only place
> with observed harm is KCOV.
> 
> Any naming suggestions? Other than really_in_interrupt or
> in_interrupt_and_not_in_bh_disabled?

Hence the suggestion to audit and fix instead of making a bigger mess :/