From: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
To: 'Christoph Lameter' <clameter@sgi.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>,
Zoltan Menyhart <Zoltan.Menyhart@bull.net>,
"Boehm, Hans" <hans.boehm@hp.com>,
"Grundler, Grant G" <grant.grundler@hp.com>,
akpm@osdl.org, linux-kernel@vger.kernel.org,
linux-ia64@vger.kernel.org
Subject: RE: Synchronizing Bit operations V2
Date: Fri, 31 Mar 2006 00:53:11 +0000 [thread overview]
Message-ID: <200603310052.k2V0qQg26856@unix-os.sc.intel.com> (raw)
In-Reply-To: <Pine.LNX.4.64.0603301639530.2068@schroedinger.engr.sgi.com>
In-Reply-To: <Pine.LNX.4.64.0603301615540.2023@schroedinger.engr.sgi.com>
Christoph Lameter wrote on Thursday, March 30, 2006 4:43 PM
> > > Note that the current semantics for bitops IA64 are broken. Both
> > > smp_mb__after/before_clear_bit are now set to full memory barriers
> > > to compensate
> >
> > Why you say that? clear_bit has built-in acq or rel semantic depends
> > on how you define it. I think only one of smp_mb__after/before need to
> > be smp_mb?
>
> clear_bit has no barrier semantics just acquire. Therefore both smp_mb_*
> need to be barriers or they need to add some form of "release".
We are talking about arch specific implementation of clear_bit and smp_mb_*.
Yes, for generic code, clear_bit has no implication of memory ordering, but
for arch specific code, one should optimize those three functions with the
architecture knowledge of exactly what's happening under the hood.
- Ken
next prev parent reply other threads:[~2006-03-31 0:53 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-03-30 21:02 Bit operations with the ability to specify a synchronization mode Christoph Lameter
2006-03-31 0:18 ` Synchronizing Bit operations V2 Christoph Lameter
2006-03-31 0:39 ` Chen, Kenneth W
2006-03-31 0:42 ` Christoph Lameter
2006-03-31 0:45 ` Christoph Lameter
2006-03-31 0:42 ` David Mosberger-Tang
2006-03-31 0:49 ` Christoph Lameter
2006-03-31 6:10 ` Chris Wright
2006-03-31 0:44 ` Nick Piggin
2006-03-31 3:28 ` Christoph Lameter
2006-03-31 4:12 ` Nick Piggin
2006-03-31 17:43 ` Christoph Lameter
2006-04-01 2:56 ` Nick Piggin
2006-03-31 0:50 ` Chen, Kenneth W
2006-03-31 0:51 ` Christoph Lameter
2006-03-31 0:53 ` Chen, Kenneth W [this message]
2006-03-31 0:55 ` Christoph Lameter
2006-03-31 0:56 ` Luck, Tony
2006-03-31 0:58 ` Christoph Lameter
2006-04-02 7:59 ` Russell King
2006-03-31 0:59 ` Chen, Kenneth W
2006-03-31 1:09 ` Christoph Lameter
2006-03-31 1:04 ` Chen, Kenneth W
2006-03-31 1:13 ` Christoph Lameter
2006-03-31 1:13 ` Chen, Kenneth W
2006-03-31 1:29 ` Chen, Kenneth W
2006-03-31 1:37 ` Christoph Lameter
2006-03-31 1:33 ` linux
2006-03-31 1:40 ` Christoph Lameter
2006-03-31 2:35 ` Chen, Kenneth W
2006-03-31 2:37 ` Christoph Lameter
2006-03-31 2:45 ` Chen, Kenneth W
2006-03-31 2:53 ` Nick Piggin
2006-03-31 3:01 ` Christoph Lameter
2006-03-31 2:51 ` Chen, Kenneth W
2006-03-31 2:55 ` Christoph Lameter
2006-03-31 3:02 ` Chen, Kenneth W
2006-03-31 3:08 ` Christoph Lameter
2006-03-31 3:10 ` Chen, Kenneth W
2006-03-31 3:12 ` Christoph Lameter
2006-03-31 3:11 ` Chen, Kenneth W
2006-03-31 3:14 ` Chen, Kenneth W
2006-03-31 3:20 ` Christoph Lameter
2006-03-31 3:17 ` Chen, Kenneth W
2006-03-31 3:23 ` Chen, Kenneth W
2006-03-31 3:37 ` Chen, Kenneth W
2006-03-31 6:15 ` Chen, Kenneth W
2006-03-31 7:34 ` Nick Piggin
2006-03-31 13:28 ` Andi Kleen
2006-03-31 16:22 ` Hans Boehm
2006-03-31 16:37 ` Andi Kleen
2006-03-31 17:46 ` Christoph Lameter
2006-03-31 17:45 ` Christoph Lameter
2006-03-31 17:48 ` Andi Kleen
2006-03-31 17:56 ` Christoph Lameter
2006-04-02 7:54 ` Russell King
2006-03-31 18:57 ` Chen, Kenneth W
2006-03-31 19:41 ` Chen, Kenneth W
2006-03-31 21:15 ` Christoph Lameter
2006-03-31 21:24 ` Chen, Kenneth W
2006-03-31 21:28 ` Christoph Lameter
2006-04-01 2:16 ` Nick Piggin
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