From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: David Howells <dhowells@redhat.com>
Cc: Pavel Machek <pavel@ucw.cz>,
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
Date: Wed, 08 Mar 2006 22:01:44 +0000 [thread overview]
Message-ID: <1141855305.10606.6.camel@localhost.localdomain> (raw)
In-Reply-To: <24309.1141848971@warthog.cambridge.redhat.com>
On Mer, 2006-03-08 at 20:16 +0000, David Howells wrote:
> The LOCK and UNLOCK functions presumably make at least one memory write apiece
> to manipulate the target lock (on SMP at least).
No they merely perform the bus transactions neccessary to perform an
update atomically. They are however "serializing" instructions which
means they do cause a certain amount of serialization (see the intel
architecture manual on serializing instructions for detail).
Athlon and later know how to turn it from locked memory accesses into
merely an exclusive cache line grab.
> > This makes it sound like pentium-III+ is incompatible with previous
> > CPUs. Is it really the case?
>
> Yes - hence the alternative instruction stuff.
It is the case for certain specialist instructions and the fences are
provided to go with those but can also help in other cases. PIII and
later in particular support explicit non temporal stores.
next prev parent reply other threads:[~2006-03-08 21:57 UTC|newest]
Thread overview: 89+ 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 18:30 ` David Howells
2006-03-07 11:13 ` Andi Kleen
2006-03-07 19:24 ` David Howells
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 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)
2006-03-07 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 12:34 ` David Howells
2006-03-08 16:40 ` Bryan O'Sullivan
2006-03-08 7:41 ` Nick Piggin
2006-03-08 13:19 ` David Howells
2006-03-08 21:49 ` Paul Mackerras
2006-03-08 22:05 ` Alan Cox
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
2006-03-08 23:08 ` Ivan Kokshaysky
2006-03-09 1:01 ` Paul Mackerras
2006-03-09 16:02 ` Ivan Kokshaysky
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 19:31 ` 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 12:27 ` David Howells
2006-03-09 11:44 ` Michael Buesch
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
2006-03-08 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 22:01 ` Paul Mackerras
2006-03-08 22:23 ` David S. Miller
2006-03-08 19:37 ` [PATCH] Document Linux's memory barriers [try #3] David Howells
2006-03-09 14:01 ` David Howells
2006-03-08 16:18 ` [PATCH] Document Linux's memory barriers Pavel Machek
2006-03-08 20:16 ` David Howells
2006-03-08 22:01 ` Alan Cox [this message]
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
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