From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Jesse Barnes <jbarnes@engr.sgi.com>
Cc: Albert Cahalan <albert@users.sourceforge.net>,
linux-kernel mailing list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] I/O space write barrier
Date: Wed, 06 Oct 2004 08:41:40 +1000 [thread overview]
Message-ID: <1097016099.27222.14.camel@gaston> (raw)
In-Reply-To: <200410050833.49654.jbarnes@engr.sgi.com>
On Wed, 2004-10-06 at 01:33, Jesse Barnes wrote:
> This macro is only supposed to deal with writes from different CPUs that may
> arrive out of order, nothing else. It sounds like PPC won't allow that
> normally, so I can be an empty definition.
I don't understand that neither. You can never guarantee any ordering
between writes from different CPUs unless you have a sinlock. If you
have an ordering problem with spinlocks, then it's a totally different
issue, a bit more like MMIO vs. cacheable mem that we have on PPC. If
this is the problem you are trying to chase, then we could use such a
barrier on ppc too and make it a hard sync, but it has nothing to do
with the write barrier we already have in our IO accessors...
> > That doesn't solve my need of MMIO vs. memory unless you are trying to
> > cover that as well, in which case it should be a sync.
>
> No, I think that has to be covered separately.
How so ? Again, this whole "ordering of writes between different CPU" makes
absolutely no sense to me.
Ben.
next prev parent reply other threads:[~2004-10-05 22:48 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-10-04 20:39 [PATCH] I/O space write barrier Albert Cahalan
2004-10-04 21:20 ` Jesse Barnes
2004-10-05 0:32 ` Albert Cahalan
2004-10-05 1:22 ` Benjamin Herrenschmidt
2004-10-05 2:26 ` Jesse Barnes
2004-10-05 3:04 ` Benjamin Herrenschmidt
2004-10-05 15:33 ` Jesse Barnes
2004-10-05 22:41 ` Benjamin Herrenschmidt [this message]
2004-10-05 23:09 ` Jesse Barnes
2004-10-05 23:57 ` Roland Dreier
2004-10-06 1:45 ` Benjamin Herrenschmidt
2004-10-05 2:33 ` Jesse Barnes
-- strict thread matches above, loose matches on Subject: below --
2004-10-21 23:13 Jesse Barnes
2004-10-22 1:01 ` Grant Grundler
2004-10-22 3:05 ` Jesse Barnes
2004-10-22 4:26 ` Greg Banks
2004-10-22 15:26 ` Grant Grundler
2004-10-05 22:38 Jesse Barnes
2004-09-27 18:03 Jesse Barnes
2004-09-29 10:36 ` Greg Banks
2004-09-29 20:35 ` David S. Miller
2004-09-29 20:43 ` Jesse Barnes
2004-09-29 20:50 ` David S. Miller
2004-09-30 2:23 ` Greg Banks
2004-09-29 22:55 ` Jesse Barnes
2004-09-30 7:15 ` Jeremy Higdon
2004-09-30 21:21 ` Guennadi Liakhovetski
2004-10-16 0:38 ` Jeremy Higdon
2004-10-16 3:20 ` Matthew Wilcox
2004-10-16 3:31 ` Jeremy Higdon
2004-09-22 15:45 Jesse Barnes
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