linux-kernel - Re: [rfc PATCH] ieee1394: ohci1394: delete bogus spinlock, flush MMIO writes

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Message-ID: <456CCB53.70208@s5r6.in-berlin.de>
Date:	Wed, 29 Nov 2006 00:50:43 +0100
From:	Stefan Richter <stefanr@...6.in-berlin.de>
To:	Alan <alan@...rguk.ukuu.org.uk>
CC:	linux1394-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [rfc PATCH] ieee1394: ohci1394: delete bogus spinlock, flush
 MMIO writes

Alan wrote:
> On Tue, 28 Nov 2006 22:24:11 +0100 (CET)
> Stefan Richter <stefanr@...6.in-berlin.de> wrote:
>> All MMIO writes which were surrounded by the spinlock as well as the
>> very last MMIO write of the IRQ handler are now explicitly flushed by
>> MMIO reads of the respective register.
> 
> MMIO is ordered anyway on the bus, you just need mmiowb() to force
> ordering to the bus controller in case you are on a big numa box.

The mmiowb is a checkpoint to ensure ordering between different threads
of MMIO writes; i.e. it doesn't halt the thread until the write actually
reached the device like a read would do, right?
-- 
Stefan Richter
-=====-=-==- =-== ===-=
http://arcgraph.de/sr/
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