linux-kernel - Re: [PATCH v4 6/8] arm: Break cyclic percpu include

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Message-ID: <20200625073145.GA7444@willie-the-truck>
Date:   Thu, 25 Jun 2020 08:31:45 +0100
From:   Will Deacon <will@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     mingo@...nel.org, tglx@...utronix.de, x86@...nel.org,
        linux-kernel@...r.kernel.org, a.darwish@...utronix.de,
        rostedt@...dmis.org, bigeasy@...utronix.de, davem@...emloft.net,
        sparclinux@...r.kernel.org, mpe@...erman.id.au,
        linuxppc-dev@...ts.ozlabs.org, heiko.carstens@...ibm.com,
        linux-s390@...r.kernel.org, linux@...linux.org.uk
Subject: Re: [PATCH v4 6/8] arm: Break cyclic percpu include

On Wed, Jun 24, 2020 at 07:53:20PM +0200, Peter Zijlstra wrote:
> On Tue, Jun 23, 2020 at 10:02:57AM +0100, Will Deacon wrote:
> > On Tue, Jun 23, 2020 at 10:36:51AM +0200, Peter Zijlstra wrote:
> > > In order to use <asm/percpu.h> in irqflags.h, we need to make sure
> > > asm/percpu.h does not itself depend on irqflags.h.
> > > 
> > > Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> > > ---
> > >  arch/arm/include/asm/percpu.h |    2 ++
> > >  1 file changed, 2 insertions(+)
> > > 
> > > --- a/arch/arm/include/asm/percpu.h
> > > +++ b/arch/arm/include/asm/percpu.h
> > > @@ -10,6 +10,8 @@
> > >   * in the TPIDRPRW. TPIDRPRW only exists on V6K and V7
> > >   */
> > >  #if defined(CONFIG_SMP) && !defined(CONFIG_CPU_V6)
> > > +register unsigned long current_stack_pointer asm ("sp");
> > 
> > If you define this unconditionally, then we can probably get rid of the
> > copy in asm/thread_info.h, rather than duplicate the same #define.
> 
> The below delta seems to build arm-allnoconfig, arm-defconfig and
> arm-allmodconfig.
> 
> Although please don't ask me how asm/thread_info.h includes asm/percpu.h
> 
> Does that work for you?

Yes, thanks! I can't believe you removed the helpful comment.

> -/*
> - * how to get the current stack pointer in C
> - */

Will