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: Thu, 09 Mar 2006 12:28:59 +0000 [thread overview]
Message-ID: <1141907339.16745.2.camel@localhost.localdomain> (raw)
In-Reply-To: <24280.1141904462@warthog.cambridge.redhat.com>
On Iau, 2006-03-09 at 11:41 +0000, David Howells wrote:
> Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
> So, you're saying that the LOCK and UNLOCK primitives don't actually modify
> memory, but rather simply pin the cacheline into the CPU's cache and refuse to
> let anyone else touch it?
Basically yes
> No... it can't work like that. It *must* make a memory modification
Then you'll have to argue with the chip designers because it doesn't.
Its all built around the cache coherency. To make a write to a cache
line I must be the sole owner of the line. Look up "MESI cache" in a
good book on the subject.
If we own the affected line then we can update just the cache and be
sure that since we own the cache line and we will write it back if
anyone else asks for it (or nowdays on some systems transfer it direct
to the other cpu) that we get locked semantics
next prev parent reply other threads:[~2006-03-09 12:23 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
2006-03-09 11:41 ` David Howells
2006-03-09 12:28 ` Alan Cox [this message]
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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