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From: Tim Deegan <tim@xen.org>
To: Ian Campbell <ian.campbell@citrix.com>
Cc: julien.grall@citrix.com, stefano.stabellini@eu.citrix.com,
	keir@xen.org, jbeuich@suse.com, xen-devel@lists.xen.org
Subject: Re: [PATCH 05/10] xen: use SMP barrier in common code dealing with shared memory protocols
Date: Thu, 4 Jul 2013 12:26:29 +0100	[thread overview]
Message-ID: <20130704112629.GG40611@ocelot.phlegethon.org> (raw)
In-Reply-To: <1372435856-14040-5-git-send-email-ian.campbell@citrix.com>

At 17:10 +0100 on 28 Jun (1372439451), Ian Campbell wrote:
> Xen currently makes no strong distinction between the SMP barriers (smp_mb
> etc) and the regular barrier (mb etc). In Linux, where we inherited these
> names from having imported Linux code which uses them, the SMP barriers are
> intended to be sufficient for implementing shared-memory protocols between
> processors in an SMP system while the standard barriers are useful for MMIO
> etc.
> 
> On x86 with the stronger ordering model there is not much practical difference
> here but ARM has weaker barriers available which are suitable for use as SMP
> barriers.
> 
> Therefore ensure that common code uses the SMP barriers when that is all which
> is required.
> 
> On both ARM and x86 both types of barrier are currently identical so there is
> no actual change. A future patch will change smp_mb to a weaker barrier on
> ARM.
> 
> Signed-off-by: Ian Campbell <ian.campbell@citrix.com>

Reviewed-by: Tim Deegan <tim@xen.org>

  parent reply	other threads:[~2013-07-04 11:26 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-06-28 16:10 [PATCH 00/10] xen: arm: map normal memory as inner shareable, reduce scope of various barriers Ian Campbell
2013-06-28 16:10 ` [PATCH 01/10] xen: arm: map memory as inner shareable Ian Campbell
2013-07-01 15:39   ` Stefano Stabellini
2013-07-01 15:42     ` Ian Campbell
2013-07-02 14:09   ` Leif Lindholm
2013-07-02 14:26     ` Ian Campbell
2013-07-04 10:58   ` Tim Deegan
2013-07-04 11:03     ` Ian Campbell
2013-06-28 16:10 ` [PATCH 02/10] xen: arm: Only upgrade guest barriers to " Ian Campbell
2013-07-01 15:24   ` Stefano Stabellini
2013-07-04 10:58   ` Tim Deegan
2013-06-28 16:10 ` [PATCH 03/10] xen: arm: reduce instruction cache and tlb flushes to inner-shareable Ian Campbell
2013-07-01 15:25   ` Stefano Stabellini
2013-07-04 11:07   ` Tim Deegan
2013-07-04 11:19     ` Tim Deegan
2013-07-04 11:21       ` Tim Deegan
2013-06-28 16:10 ` [PATCH 04/10] xen: arm: consolidate barrier definitions Ian Campbell
2013-07-01 15:25   ` Stefano Stabellini
2013-07-04 11:07   ` Tim Deegan
2013-06-28 16:10 ` [PATCH 05/10] xen: use SMP barrier in common code dealing with shared memory protocols Ian Campbell
2013-06-28 16:15   ` Ian Campbell
2013-06-28 16:20   ` Keir Fraser
2013-07-04 11:26   ` Tim Deegan [this message]
2013-06-28 16:10 ` [PATCH 06/10] xen: arm: Use SMP barriers when that is all which is required Ian Campbell
2013-07-01 15:19   ` Stefano Stabellini
2013-07-01 15:24     ` Ian Campbell
2013-07-04 11:30       ` Tim Deegan
2013-06-28 16:10 ` [PATCH 07/10] xen: arm: Use dmb for smp barriers Ian Campbell
2013-07-01 15:20   ` Stefano Stabellini
2013-07-04 11:31   ` Tim Deegan
2013-06-28 16:10 ` [PATCH 08/10] xen: arm: add scope to dsb and dmb macros Ian Campbell
2013-07-01 15:21   ` Stefano Stabellini
2013-07-01 15:22     ` Stefano Stabellini
2013-07-04 11:44   ` (no subject) Tim Deegan
2013-06-28 16:10 ` [PATCH 09/10] xen: arm: weaken SMP barriers to inner shareable Ian Campbell
2013-07-01 15:21   ` Stefano Stabellini
2013-07-01 15:22     ` Stefano Stabellini
2013-07-04 11:35   ` Tim Deegan
2013-06-28 16:10 ` [PATCH 10/10] xen: arm: use more specific barriers for read and write barriers Ian Campbell
2013-07-01 15:22   ` Stefano Stabellini
2013-07-04 11:42   ` Tim Deegan
2013-07-04 11:46     ` Ian Campbell
2013-06-28 16:11 ` [PATCH 00/10] xen: arm: map normal memory as inner shareable, reduce scope of various barriers Ian Campbell
2013-07-04 11:32 (no subject) Tim Deegan

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