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Date: Sat, 12 Mar 2005 10:28:20 -0800
From: Sam Leffler <sam@errno.com>
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To: Andre Oppermann <andre@freebsd.org>
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cc: dima <_pppp@mail.ru>
cc: Pawel Jakub Dawidek <pjd@freebsd.org>
cc: John Baldwin <jhb@freebsd.org>
cc: Luigi Rizzo <rizzo@icir.org>
cc: rwatson@freebsd.org
cc: Julian Elischer <julian@elischer.org>
cc: net@freebsd.org
Subject: Re: Giant-free polling [PATCH]
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Andre Oppermann wrote:
> Sam Leffler wrote:
> 
>>Pawel Jakub Dawidek wrote:
>>
>>>On Fri, Mar 11, 2005 at 01:14:38PM -0800, Julian Elischer wrote:
>>>+> >P> There is still an unresolved problem (in your and our patch as well) of
>>>+> >P> using ifnet structure fields without synchronization, as we don't have
>>>+> >P> access tointerface's internal mutex, which protects those fields.
>>>+> >
>>>+> >
>>>+>
>>>+> you need to add an interface method that has access to it..
>>>
>>>I was thinking more about moving interface mutex into ifnet structure,
>>>but Robert has some objections IIRC.
>>>
>>
>>I don't know what Robert's objections are but I've considered doing it
>>for a while to deal with some locking issues in net80211-based drivers.
>>  The only issue I can see is if this mutex boxes drivers into a locking
>>model that interlocks the rx+tx paths.
> 
> 
> We don't want this.  This would paint us into a corner with modern
> high speed hardware that can hanle the rx+tx paths simulaneously.
> Depending on the hardware DMA model and driver architecture you
> want to have a different locking model.  I agree with Robert in
> objecting to this.
>


You did not read what I wrote.  The ath driver has separate tx+rx paths 
and it could benefit from the mutex being in the ifnet structure.

	Sam