From: Paul Mackerras <paulus@samba.org>
To: David Howells <dhowells@redhat.com>
Cc: Matthew Wilcox <matthew@wil.cx>, Alan Cox <alan@redhat.com>,
torvalds@osdl.org, akpm@osdl.org, mingo@redhat.com,
linux-arch@vger.kernel.org, linuxppc64-dev@ozlabs.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Document Linux's memory barriers [try #2]
Date: Thu, 9 Mar 2006 09:10:49 +1100 [thread overview]
Message-ID: <17423.22121.254026.487964@cargo.ozlabs.ibm.com> (raw)
In-Reply-To: <10095.1141838381@warthog.cambridge.redhat.com>
David Howells writes:
> > # define smp_read_barrier_depends() do { } while(0)
>
> What's this one meant to do?
On most CPUs, if you load one value and use the value you get to
compute the address for a second load, there is an implicit read
barrier between the two loads because of the dependency. That's not
true on alpha, apparently, because of the way their caches are
structured. The smp_read_barrier_depends is a read barrier that you
use between two loads when there is already a dependency between the
loads, and it is a no-op on everything except alpha (IIRC).
Paul.
next prev parent reply other threads:[~2006-03-08 22:11 UTC|newest]
Thread overview: 98+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-03-07 17:40 [PATCH] Document Linux's memory barriers David Howells
2006-03-07 10:34 ` Andi Kleen
2006-03-07 17:47 ` Stephen Hemminger
2006-03-07 18:30 ` David Howells
2006-03-07 11:13 ` Andi Kleen
2006-03-07 18:46 ` Jesse Barnes
2006-03-07 19:23 ` Bryan O'Sullivan
2006-03-07 11:57 ` Andi Kleen
2006-03-07 20:01 ` Jesse Barnes
2006-03-07 21:14 ` Bryan O'Sullivan
2006-03-07 21:24 ` Andi Kleen
2006-03-08 0:36 ` Alan Cox
2006-03-08 0:35 ` Alan Cox
2006-03-07 19:24 ` David Howells
2006-03-07 19:46 ` Stephen Hemminger
2006-03-07 18:40 ` Alan Cox
2006-03-07 18:54 ` linux-os (Dick Johnson)
2006-03-07 19:06 ` Matthew Wilcox
2006-03-07 19:15 ` linux-os (Dick Johnson)
2006-03-09 11:26 ` Sergei Organov
2006-03-07 19:33 ` Alan Cox
2006-03-07 20:09 ` David Howells
2006-03-08 0:32 ` Alan Cox
2006-03-08 8:25 ` Duncan Sands
2006-03-08 22:06 ` Paul Mackerras
2006-03-08 22:24 ` David S. Miller
2006-03-08 22:31 ` Linus Torvalds
2006-03-08 22:42 ` Alan Cox
2006-03-08 2:07 ` Nick Piggin
2006-03-08 3:10 ` Paul Mackerras
2006-03-08 3:30 ` Linus Torvalds
2006-03-08 7:41 ` Nick Piggin
2006-03-08 12:34 ` David Howells
2006-03-08 16:40 ` Bryan O'Sullivan
2006-03-08 13:19 ` David Howells
2006-03-08 21:49 ` Paul Mackerras
2006-03-08 22:05 ` Alan Cox
2006-03-10 0:49 ` H. Peter Anvin
2006-03-08 14:37 ` [PATCH] Document Linux's memory barriers [try #2] David Howells
2006-03-08 14:55 ` Alan Cox
2006-03-08 15:41 ` Matthew Wilcox
2006-03-08 17:19 ` David Howells
2006-03-08 22:10 ` Paul Mackerras [this message]
2006-03-08 23:08 ` Ivan Kokshaysky
2006-03-09 1:01 ` Paul Mackerras
2006-03-09 16:02 ` Ivan Kokshaysky
2006-03-08 22:01 ` Paul Mackerras
2006-03-08 22:23 ` David S. Miller
2006-03-08 17:04 ` David Howells
2006-03-08 17:36 ` Alan Cox
2006-03-08 18:35 ` David Howells
2006-03-08 18:45 ` Alan Cox
2006-03-08 18:59 ` David Howells
2006-03-08 11:38 ` Andi Kleen
2006-03-08 19:08 ` David Howells
2006-03-08 19:26 ` Linus Torvalds
2006-03-08 19:40 ` Matthew Wilcox
2006-03-09 0:37 ` Paul Mackerras
2006-03-09 0:59 ` Jesse Barnes
2006-03-09 1:36 ` Paul Mackerras
2006-03-09 4:18 ` Jesse Barnes
2006-03-08 19:54 ` Jesse Barnes
2006-03-08 20:02 ` Alan Cox
2006-03-08 19:31 ` David Howells
2006-03-09 0:35 ` Paul Mackerras
2006-03-09 0:54 ` Linus Torvalds
2006-03-09 1:08 ` Paul Mackerras
2006-03-09 1:27 ` Linus Torvalds
2006-03-09 2:38 ` Nick Piggin
2006-03-09 3:45 ` Paul Mackerras
2006-03-09 4:36 ` Jesse Barnes
2006-03-09 7:41 ` Paul Mackerras
2006-03-09 5:38 ` Linus Torvalds
2006-03-09 11:44 ` Michael Buesch
2006-03-09 12:27 ` David Howells
2006-03-09 4:34 ` Jesse Barnes
2006-03-09 4:43 ` Paul Mackerras
2006-03-09 10:05 ` Jes Sorensen
2006-03-09 0:55 ` Jesse Barnes
2006-03-09 1:57 ` Paul Mackerras
2006-03-09 4:26 ` Jesse Barnes
2006-03-09 12:02 ` Sergei Organov
2006-03-08 16:18 ` [PATCH] Document Linux's memory barriers Pavel Machek
2006-03-08 16:26 ` Christoph Lameter
2006-03-08 17:35 ` David Howells
2006-03-08 17:46 ` Christoph Lameter
2006-03-08 17:59 ` Alan Cox
2006-03-08 19:37 ` [PATCH] Document Linux's memory barriers [try #3] David Howells
2006-03-08 20:16 ` [PATCH] Document Linux's memory barriers David Howells
2006-03-08 22:01 ` Alan Cox
2006-03-09 11:41 ` David Howells
2006-03-09 12:28 ` Alan Cox
2006-03-09 13:02 ` David Howells
2006-03-09 16:32 ` Linus Torvalds
2006-03-09 17:39 ` David Howells
2006-03-09 17:54 ` Linus Torvalds
2006-03-09 17:56 ` Linus Torvalds
2006-03-09 14:01 ` [PATCH] Document Linux's memory barriers [try #3] David Howells
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