linux-kernel - Re: [PATCH 3/3 V2] pvclock: Get rid of __pvclock_read_cycles in function pvclock_read

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Date:	Thu, 9 Jun 2016 13:28:07 +0200
From:	Borislav Petkov <bp@...e.de>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	Minfei Huang <mnghuan@...il.com>, luto@...nel.org, hpa@...or.com,
	mingo@...hat.com, tglx@...utronix.de, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3 V2] pvclock: Get rid of __pvclock_read_cycles in
 function pvclock_read_flags

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)
--