linux-kernel - Re: [PATCH 6/6] percpu: Add preemption checks to __this

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Message-ID: <00000141c1fae3ba-6b52fea1-74f9-42f7-b1db-70dda847e7f9-000000@email.amazonses.com>
Date:	Wed, 16 Oct 2013 15:55:47 +0000
From:	Christoph Lameter <cl@...ux.com>
To:	Peter Zijlstra <peterz@...radead.org>
cc:	Tejun Heo <tj@...nel.org>, akpm@...uxfoundation.org,
	rostedt@...dmis.org, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 6/6] percpu: Add preemption checks to __this_cpu ops

On Wed, 16 Oct 2013, Peter Zijlstra wrote:

> On Wed, Oct 16, 2013 at 03:09:13PM +0000, Christoph Lameter wrote:
> > On Wed, 16 Oct 2013, Peter Zijlstra wrote:
> >
> > > So I didn't understand what was wrong with:
> > >
> > > #define __this_cpu_read(pcp) \
> > > 	(__this_cpu_preempt_check("read"), raw_this_cpu_read(pcp))
> > >
> > > And idem for all others. This is 1) shorter to write; and 2) makes it
> > > blindingly obvious that the implementations are actually the same.
> >
> > Nothing wrong with that. It just increases the scope of this patch to
> > require modifications to arch code and I already have trouble enough
> > following through on all the issues that were raised so far.
> >
>
> But non of your raw ops touch arch code... /me confused.

Yes that is intentional to limit scope. Renaming would require arch
changes.

The __this_cpu_xxxs are defined in arch code. Look at x86 arch
implementations for example. arch/x86/include/asm/percpu.h. s390 also has
this. Not sure if other arches do.



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