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Date:   Sat, 18 May 2019 10:47:20 +0100
From:   Catalin Marinas <catalin.marinas@arm.com>
To:     Dmitry Vyukov <dvyukov@google.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Dmitry Vyukov <dvyukov@gmail.com>,
        Linux-MM <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] kmemleak: fix check for softirq context
Message-ID: <20190518094719.gyvhbdrwmcv4diax@mbp>
References: <20190517171507.96046-1-dvyukov@gmail.com>
 <20190517143746.2157a759f65b4cbc73321124@linux-foundation.org>
 <CACT4Y+aee_Kvezo8zeD77RwBi2-Csd9cE8vtGCmaTGYxr=iK5A@mail.gmail.com>
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On Sat, May 18, 2019 at 09:10:59AM +0200, Dmitry Vyukov wrote:
> On Fri, May 17, 2019 at 11:37 PM Andrew Morton
> <akpm@linux-foundation.org> wrote:
> > On Fri, 17 May 2019 19:15:07 +0200 Dmitry Vyukov <dvyukov@gmail.com> wrote:
> >
> > > From: Dmitry Vyukov <dvyukov@google.com>
> > >
> > > in_softirq() is a wrong predicate to check if we are in a softirq context.
> > > It also returns true if we have BH disabled, so objects are falsely
> > > stamped with "softirq" comm. The correct predicate is in_serving_softirq().
> > >
> > > ...
> > >
> > > --- a/mm/kmemleak.c
> > > +++ b/mm/kmemleak.c
> > > @@ -588,7 +588,7 @@ static struct kmemleak_object *create_object(unsigned long ptr, size_t size,
> > >       if (in_irq()) {
> > >               object->pid = 0;
> > >               strncpy(object->comm, "hardirq", sizeof(object->comm));
> > > -     } else if (in_softirq()) {
> > > +     } else if (in_serving_softirq()) {
> > >               object->pid = 0;
> > >               strncpy(object->comm, "softirq", sizeof(object->comm));
> > >       } else {
> >
> > What are the user-visible runtime effects of this change?
> 
> If user does cat from /sys/kernel/debug/kmemleak previously they would
> see this, which is clearly wrong, this is system call context (see the
> comm):

Indeed, with your patch you get the correct output.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>

Thanks.

-- 
Catalin