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Re: [PATCH 3/3 V2] pvclock: Get rid of __pvclock_read_cycles in function pvclock_read_flags

From Borislav Petkov <bp@suse.de>
Newsgroups linux.kernel
Subject Re: [PATCH 3/3 V2] pvclock: Get rid of __pvclock_read_cycles in function pvclock_read_flags
Date 2016-06-09 13:30 +0200
Message-ID <rI6jU-5Fr-11@gated-at.bofh.it> (permalink)
References <rDjhL-8fO-3@gated-at.bofh.it> <rDLxn-rd-1@gated-at.bofh.it> <rHGSu-685-31@gated-at.bofh.it> <rI6jU-5Fr-7@gated-at.bofh.it>
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On Thu, Jun 09, 2016 at 01:21:18PM +0200, Paolo Bonzini wrote:
> This is basically implementing a seqcount.  It needs two barriers and,

Why does it need the two barriers? More details please.

> technically, they should be virt_rmb() -- it really doesn't matter of
> course because reads are never reordered on x86.

You mean

	version = src->version;
	flags = src->flags;

are not reordered?

I don't think so.

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
-- 

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Thread

Re: [PATCH 3/3 V2] pvclock: Get rid of __pvclock_read_cycles in  function pvclock_read_flags Borislav Petkov <bp@suse.de> - 2016-06-08 10:20 +0200
  Re: [PATCH 3/3 V2] pvclock: Get rid of __pvclock_read_cycles in  function pvclock_read_flags Paolo Bonzini <pbonzini@redhat.com> - 2016-06-09 13:30 +0200
    Re: [PATCH 3/3 V2] pvclock: Get rid of __pvclock_read_cycles in  function pvclock_read_flags Borislav Petkov <bp@suse.de> - 2016-06-09 13:30 +0200
      Re: [PATCH 3/3 V2] pvclock: Get rid of __pvclock_read_cycles in  function pvclock_read_flags Paolo Bonzini <pbonzini@redhat.com> - 2016-06-09 14:40 +0200

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