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Date:      Thu, 20 Jul 2000 15:05:27 -0700
From:      David Greenman <dg@root.com>
To:        Mike Smith <msmith@FreeBSD.ORG>
Cc:        =?ISO-8859-1?Q?G=E9rard_Roudier?= <groudier@club-internet.fr>, freebsd-alpha@FreeBSD.ORG
Subject:   Re: fxp0 hangs on a PC164 using STABLE 
Message-ID:  <200007202205.PAA07882@implode.root.com>
In-Reply-To: Your message of "Thu, 20 Jul 2000 15:00:59 PDT." <200007202201.PAA00657@mass.osd.bsdi.com> 

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>> As a result ( applying to my opinion ;-) ), when a PCI device and its
>> software driver communicates through the main memory, it is _very_ likely
>> memory barrier to be needed in some places so that program-expected
>> ordering as seen from the system BUS will happen.
>
>I am inclined to agree with you that there are probably cases in the fxp 
>driver where the author has made assumptions regarding the x86 normal 
>behaviour of retiring writes in program order, however that's not the 
>issue that this change is trying to address.

   That is correct. The author assumed that writes would be retired in
order and without any special memory barriers or other synchronization.

-DG

David Greenman
Co-founder, The FreeBSD Project - http://www.freebsd.org
Manufacturer of high-performance Internet servers - http://www.terasolutions.com
Pave the road of life with opportunities.


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