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Re: [PATCH v2] futex: replace bare barrier() with a READ_ONCE()

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On Wed, Mar 2, 2016 at 9:35 PM, Christian Borntraeger
<borntraeger@de.ibm.com> wrote:
> That change makes sense. I did the original barrier back in 2006 (could you cc me next time?)

Sorry for that,  I thought get_maintainer.pl would had spit the
original author's email, but apparently it didn't :(

> ACCESS_ONCE or READ_ONCE was not available at that time and its now the better way.
>
> This is not an s390 specific problem, it was just triggered there as the gcc cost model
> considered the memory read as cheap as a register read.
>

Thanks for the clarification.

> Maybe simplify the comment to something like
>
>         /* Prevent the compiler to read lock_ptr twice (if and spin_lock) */

Will do.


Regards,
Jianyu Zhan

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[PATCH v2] futex:  replace bare barrier() with a READ_ONCE() Jianyu Zhan <nasa4836@gmail.com> - 2016-03-02 14:10 +0100
  Re: [PATCH v2] futex: replace bare barrier() with a READ_ONCE() Christian Borntraeger <borntraeger@de.ibm.com> - 2016-03-02 14:40 +0100
    Re: [PATCH v2] futex: replace bare barrier() with a READ_ONCE() Jianyu Zhan <nasa4836@gmail.com> - 2016-03-02 15:00 +0100
      Re: [PATCH v2] futex: replace bare barrier() with a READ_ONCE() Darren Hart <dvhart@infradead.org> - 2016-03-02 17:50 +0100
  Re: [PATCH v2] futex:  replace bare barrier() with a READ_ONCE() Darren Hart <dvhart@infradead.org> - 2016-03-02 17:50 +0100

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