linux-kernel - Re: blackfin - cmpxchg not atomic ?

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Date:	Sat, 21 Jul 2007 04:37:35 -0400
From:	"Mike Frysinger" <vapier.adi@...il.com>
To:	"Robert Schwebel" <r.schwebel@...gutronix.de>
Cc:	"Mathieu Desnoyers" <mathieu.desnoyers@...ymtl.ca>,
	tonyko@...eo.ca, robin.getz@...log.com,
	linux-kernel@...r.kernel.org
Subject: Re: blackfin - cmpxchg not atomic ?

On 7/21/07, Robert Schwebel <r.schwebel@...gutronix.de> wrote:
> On Fri, Jul 20, 2007 at 04:36:12PM -0400, Mike Frysinger wrote:
> > > Also, does you assembly stub _really_ modify memory atomically ? If yes,
> > > then there should be no need for disabling interrupts. Else, I see a
> > > major problem with SMP.
> >
> > that isnt the only problem with SMP on Blackfin
>
> Could you ealborate?

i'm pretty sure there's already been a thread on LKML about it ... the
fact that our parts currently lack any sort of cache snooping or
control over any other is a huge issue.

we've contracted a company to do SMP, but it'll have quite a bit of
overhead since it'll need to do a lot of communication/message passing
between cores to account for these hardware deficiencies.
-mike
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