From: Jesse Barnes <jbarnes@engr.sgi.com>
To: James Bottomley <James.Bottomley@steeleye.com>
Cc: "David S. Miller" <davem@davemloft.net>,
David Howells <dhowells@redhat.com>,
matthew@wil.cx, anton@samba.org, linux-arch@vger.kernel.org
Subject: Re: [PATCH] ?mb() -> smp_?mb() conversion
Date: Tue, 22 Mar 2005 10:09:09 -0800 [thread overview]
Message-ID: <200503221009.10046.jbarnes@engr.sgi.com> (raw)
In-Reply-To: <1111513463.5520.53.camel@mulgrave>
On Tuesday, March 22, 2005 9:44 am, James Bottomley wrote:
> As an aside, the main ordering problem it prevents is the SMP one where
> two CPUs do writes into the PCI domain that they order with spinlocks.
> Even though, temporally, the writes are sequenced leaving the CPUs, the
> altix PCI domain can still re-order them if the mmiowb() isn't present
> (so it sounds like it's really a smp_mmiowb()...)
Correct. And it's necessary because spin_unlock* don't do any I/O ordering by
default (in fact they're only one way memory barriers on alpha and ia64
iirc).
Jesse
next prev parent reply other threads:[~2005-03-22 18:09 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-03-21 22:59 [PATCH] ?mb() -> smp_?mb() conversion Anton Blanchard
2005-03-21 23:06 ` David S. Miller
2005-03-22 10:43 ` David Howells
2005-03-22 13:13 ` Matthew Wilcox
2005-03-22 14:27 ` David Howells
2005-03-22 16:03 ` Anton Blanchard
2005-03-22 16:34 ` Matthew Wilcox
2005-03-22 16:48 ` David Howells
2005-03-22 17:13 ` David S. Miller
2005-03-22 17:44 ` James Bottomley
2005-03-22 18:09 ` Jesse Barnes [this message]
2005-03-22 18:00 ` David Howells
2005-03-22 21:59 ` Paul Mackerras
2005-03-22 18:15 ` Jesse Barnes
2005-03-22 18:24 ` Jesse Barnes
2005-03-23 6:23 ` Paul Mackerras
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