linux-kernel - Re: [PATCH 0/2] Use named address spaces for percpu data

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Date:   Wed, 12 Sep 2018 23:06:30 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Richard Henderson <rth@...ddle.net>
Cc:     Matthew Wilcox <willy@...radead.org>,
        Waiman Long <longman@...hat.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH 0/2] Use named address spaces for percpu data


* Richard Henderson <rth@...ddle.net> wrote:

> On 09/12/2018 07:44 AM, Matthew Wilcox wrote:
> > rth wrote a patch back in 2016 that uses gcc's address space machinery
> > to improve code generation for percpu accesses.  Ingo asked for some
> > minor changes to be made, but Richard didn't respond.  While looking at
> > something related, I came across them, and asked Richard's permission
> > to resurrect and resend the patch, with the changes Ingo asked for at
> > the time.
> > 
> > The important information about why we want these patch is in 1/2.
> > 
> > Richard Henderson (2):
> >   x86: Use named address spaces in asm/percpu.h
> >   x86: Enable named address spaces for percpu data
> > 
> >  arch/x86/include/asm/percpu.h | 147 ++++++++++++++++++++--------------
> >  1 file changed, 88 insertions(+), 59 deletions(-)
> 
> Thanks for resurrecting this, Willy.  I'd totally forgotten about it.
> The adjustments you made look fine.

Not all GCC versions seem to like this series:

 In file included from arch/x86/mm/tlb.c:12:0:
 arch/x86/mm/tlb.c: In function ‘switch_mm_irqs_off’:
 ./arch/x86/include/asm/mmu_context.h:210:28: internal compiler error: Segmentation fault
  #define switch_mm_irqs_off switch_mm_irqs_off
 arch/x86/mm/tlb.c:183:6: note: in expansion of macro ‘switch_mm_irqs_off’
  void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
 Please submit a full bug report,
 with preprocessed source if appropriate.
 See <file:///usr/share/doc/gcc-7/README.Bugs> for instructions.

gcc version 7.3.0 (Ubuntu 7.3.0-16ubuntu3) 

Thanks,

	Ingo