From: Davide Libenzi <davidel@xmailserver.org>
To: linux-ia64@vger.kernel.org
Subject: RE: [Linux-ia64] Re: web page on O(1) scheduler
Date: Sat, 24 May 2003 14:43:12 +0000 [thread overview]
Message-ID: <marc-linux-ia64-105590723706029@msgid-missing> (raw)
In-Reply-To: <marc-linux-ia64-105590723705966@msgid-missing>
On Fri, 23 May 2003, Davide Libenzi wrote:
> You need a write memory barrier even on the unlock. Consider this :
>
> spinlock = 1;
> ...
> protected_resource = NEWVAL;
> spinlock = 0;
>
> ( where spinlock = 0/1 strip down, but do not lose the concept, the lock
> operation ). If a CPU reorder those writes, another CPU might see the lock
> drop before the protected resource assignment. And this is usually bad
> for obvious reasons.
David made me notice about a brain misfire here. You need protection even
for loads crossing the unlock. For the same obvious reasons :) Yes, a
realease barrier will be sufficent for ia64, while you'll need an mfence
on P4.
- Davide
next prev parent reply other threads:[~2003-05-24 14:43 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-05-21 9:01 [Linux-ia64] Re: web page on O(1) scheduler Arjan van de Ven
2003-05-21 9:26 ` Mike Galbraith
2003-05-21 9:30 ` Mike Galbraith
2003-05-21 10:40 ` Duraid Madina
2003-05-21 10:43 ` Christoph Hellwig
2003-05-21 15:18 ` David Mosberger
2003-05-21 17:56 ` David Mosberger
2003-05-21 20:46 ` Mike Galbraith
2003-05-22 0:38 ` Rik van Riel
2003-05-22 5:52 ` Mike Galbraith
2003-05-22 9:52 ` Mike Galbraith
2003-05-22 16:25 ` Mike Galbraith
2003-05-22 17:58 ` David Mosberger
2003-05-23 1:07 ` Hans Boehm
2003-05-23 8:30 ` Arjan van de Ven
2003-05-23 17:48 ` Boehm, Hans
2003-05-23 18:04 ` Davide Libenzi
2003-05-24 0:10 ` Boehm, Hans
2003-05-24 0:20 ` Davide Libenzi
2003-05-24 0:53 ` Boehm, Hans
2003-05-24 5:38 ` Davide Libenzi
2003-05-24 14:43 ` Davide Libenzi [this message]
2003-05-24 16:50 ` Hans Boehm
2003-05-24 21:41 ` Davide Libenzi
2003-05-25 9:17 ` Mike Galbraith
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