From: Christoph Lameter <clameter@sgi.com>
To: Paul Mackerras <paulus@samba.org>
Cc: Satyam Sharma <satyam@infradead.org>,
Stefan Richter <stefanr@s5r6.in-berlin.de>,
Chris Snook <csnook@redhat.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-arch@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>,
netdev@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>,
ak@suse.de, heiko.carstens@de.ibm.com, davem@davemloft.net,
schwidefsky@de.ibm.com, wensong@linux-vs.org, horms@verge.net.au,
wjiang@resilience.com, cfriesen@nortel.com, zlynx@acm.org,
rpjday@mindspring.com, jesper.juhl@gmail.com,
segher@kernel.crashing.org,
Herbert Xu <herbert@gondor.apana.org.au>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures
Date: Wed, 15 Aug 2007 17:40:33 -0700 (PDT) [thread overview]
Message-ID: <Pine.LNX.4.64.0708151736180.10497@schroedinger.engr.sgi.com> (raw)
In-Reply-To: <18115.39815.730873.346526@cargo.ozlabs.ibm.com>
On Thu, 16 Aug 2007, Paul Mackerras wrote:
> Those barriers are for when we need ordering between atomic variables
> and other memory locations. An atomic variable by itself doesn't and
> shouldn't need any barriers for other CPUs to be able to see what's
> happening to it.
It does not need any barriers. As soon as one cpu acquires the
cacheline for write it will be invalidated in the caches of the others. So
the other cpu will have to refetch. No need for volatile.
The issue here may be that the compiler has fetched the atomic variable
earlier and put it into a register. However, that prefetching is limited
because it cannot cross functions calls etc. The only problem could be
loops where the compiler does not refetch the variable since it assumes
that it does not change and there are no function calls in the body of the
loop. But AFAIK these loops need cpu_relax and other measures anyways to
avoid bad effects from busy waiting.
next prev parent reply other threads:[~2007-08-16 0:41 UTC|newest]
Thread overview: 333+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-08-09 13:14 [PATCH 0/24] make atomic_read() behave consistently across all architectures Chris Snook
2007-08-09 12:41 ` Arnd Bergmann
2007-08-09 14:29 ` Chris Snook
2007-08-09 15:30 ` Arnd Bergmann
2007-08-14 22:31 ` Christoph Lameter
2007-08-14 22:45 ` Chris Snook
2007-08-14 22:51 ` Christoph Lameter
2007-08-14 23:08 ` Satyam Sharma
2007-08-14 23:04 ` Chris Snook
2007-08-14 23:14 ` Christoph Lameter
2007-08-15 6:49 ` Herbert Xu
2007-08-15 6:49 ` Herbert Xu
2007-08-15 8:18 ` Heiko Carstens
2007-08-15 13:53 ` Stefan Richter
2007-08-15 14:35 ` Satyam Sharma
2007-08-15 14:52 ` Herbert Xu
2007-08-15 16:09 ` Stefan Richter
2007-08-15 16:27 ` Paul E. McKenney
2007-08-15 17:13 ` Satyam Sharma
2007-08-15 18:31 ` Segher Boessenkool
2007-08-15 18:57 ` Paul E. McKenney
2007-08-15 19:54 ` Satyam Sharma
2007-08-15 20:17 ` Paul E. McKenney
2007-08-15 20:52 ` Segher Boessenkool
2007-08-15 22:42 ` Paul E. McKenney
2007-08-15 20:47 ` Segher Boessenkool
2007-08-16 0:36 ` Satyam Sharma
2007-08-16 0:36 ` (unknown) Satyam Sharma
2007-08-16 0:32 ` your mail Herbert Xu
2007-08-16 0:58 ` [PATCH 0/24] make atomic_read() behave consistently across all architectures Satyam Sharma
2007-08-16 0:51 ` Herbert Xu
2007-08-16 1:18 ` Satyam Sharma
2007-08-16 1:38 ` Segher Boessenkool
2007-08-15 21:05 ` [PATCH 0/24] make atomic_read() behave consistently across all architectures Segher Boessenkool
2007-08-15 22:44 ` Paul E. McKenney
2007-08-16 1:23 ` Segher Boessenkool
2007-08-16 2:22 ` Paul E. McKenney
2007-08-15 19:58 ` Stefan Richter
2007-08-16 0:39 ` [PATCH] i386: Fix a couple busy loops in mach_wakecpu.h:wait_for_init_deassert() Satyam Sharma
2007-08-24 11:59 ` Denys Vlasenko
2007-08-24 12:07 ` Andi Kleen
2007-08-24 12:12 ` Kenn Humborg
2007-08-24 12:12 ` Kenn Humborg
2007-08-24 14:25 ` Denys Vlasenko
2007-08-24 17:34 ` Linus Torvalds
2007-08-24 13:30 ` Satyam Sharma
2007-08-24 17:06 ` Christoph Lameter
2007-08-24 20:26 ` Denys Vlasenko
2007-08-24 20:34 ` Chris Snook
2007-08-24 16:19 ` Luck, Tony
2007-08-24 16:19 ` Luck, Tony
2007-08-15 16:13 ` [PATCH 0/24] make atomic_read() behave consistently across all architectures Chris Snook
2007-08-15 23:40 ` Herbert Xu
2007-08-15 23:51 ` Paul E. McKenney
2007-08-16 1:30 ` Segher Boessenkool
2007-08-16 2:30 ` Paul E. McKenney
2007-08-16 19:33 ` Segher Boessenkool
2007-08-16 1:26 ` Segher Boessenkool
2007-08-16 2:23 ` Nick Piggin
2007-08-16 19:32 ` Segher Boessenkool
2007-08-17 2:19 ` Nick Piggin
2007-08-17 3:16 ` Paul Mackerras
2007-08-17 3:32 ` Nick Piggin
2007-08-17 3:50 ` Linus Torvalds
2007-08-17 23:59 ` Paul E. McKenney
2007-08-18 0:09 ` Herbert Xu
2007-08-18 1:08 ` Paul E. McKenney
2007-08-18 1:24 ` Christoph Lameter
2007-08-18 1:41 ` Satyam Sharma
2007-08-18 4:13 ` Linus Torvalds
2007-08-18 13:36 ` Satyam Sharma
2007-08-18 21:54 ` Paul E. McKenney
2007-08-18 22:41 ` Linus Torvalds
2007-08-18 23:19 ` Paul E. McKenney
2007-08-24 12:19 ` Denys Vlasenko
2007-08-24 17:19 ` Linus Torvalds
2007-08-18 21:56 ` Paul E. McKenney
2007-08-20 13:31 ` Chris Snook
2007-08-20 22:04 ` Segher Boessenkool
2007-08-20 22:48 ` Russell King
2007-08-20 23:02 ` Segher Boessenkool
2007-08-21 0:05 ` Paul E. McKenney
2007-08-21 7:08 ` Russell King
2007-08-21 7:05 ` Russell King
2007-08-21 9:33 ` Paul Mackerras
2007-08-21 11:37 ` Andi Kleen
2007-08-21 14:48 ` Segher Boessenkool
2007-08-21 16:16 ` Paul E. McKenney
2007-08-21 22:51 ` Valdis.Kletnieks
2007-08-22 0:50 ` Paul E. McKenney
2007-08-22 21:38 ` Adrian Bunk
2007-08-21 14:39 ` Segher Boessenkool
2007-08-17 3:42 ` Linus Torvalds
2007-08-17 5:18 ` Paul E. McKenney
2007-08-17 5:56 ` Satyam Sharma
2007-08-17 7:26 ` Nick Piggin
2007-08-17 8:47 ` Satyam Sharma
2007-08-17 9:15 ` Nick Piggin
2007-08-17 10:12 ` Satyam Sharma
2007-08-17 12:14 ` Nick Piggin
2007-08-17 13:05 ` Satyam Sharma
2007-08-17 9:48 ` Paul Mackerras
2007-08-17 10:23 ` Satyam Sharma
2007-08-17 22:49 ` Segher Boessenkool
2007-08-17 23:51 ` Satyam Sharma
2007-08-17 23:55 ` Segher Boessenkool
2007-08-17 6:42 ` Geert Uytterhoeven
2007-08-17 8:52 ` Andi Kleen
2007-08-17 10:08 ` Satyam Sharma
2007-08-17 22:29 ` Segher Boessenkool
2007-08-17 17:37 ` Segher Boessenkool
2007-08-14 23:26 ` Paul E. McKenney
2007-08-15 10:35 ` Stefan Richter
2007-08-15 12:04 ` Herbert Xu
2007-08-15 12:31 ` Satyam Sharma
2007-08-15 13:08 ` Stefan Richter
2007-08-15 13:11 ` Stefan Richter
2007-08-15 13:47 ` Satyam Sharma
2007-08-15 14:25 ` Paul E. McKenney
2007-08-15 15:33 ` Herbert Xu
2007-08-15 16:08 ` Paul E. McKenney
2007-08-15 17:18 ` Satyam Sharma
2007-08-15 17:33 ` Paul E. McKenney
2007-08-15 18:05 ` Satyam Sharma
2007-08-15 17:55 ` Satyam Sharma
2007-08-15 19:07 ` Paul E. McKenney
2007-08-15 21:07 ` Segher Boessenkool
2007-08-15 20:58 ` Segher Boessenkool
2007-08-15 18:19 ` David Howells
2007-08-15 18:45 ` Paul E. McKenney
2007-08-15 23:41 ` Herbert Xu
2007-08-15 23:53 ` Paul E. McKenney
2007-08-16 0:12 ` Herbert Xu
2007-08-16 0:23 ` Paul E. McKenney
2007-08-16 0:30 ` Herbert Xu
2007-08-16 0:49 ` Paul E. McKenney
2007-08-16 0:53 ` Herbert Xu
2007-08-16 1:14 ` Paul E. McKenney
2007-08-15 18:31 ` Segher Boessenkool
2007-08-15 19:40 ` Satyam Sharma
2007-08-15 20:42 ` Segher Boessenkool
2007-08-16 1:23 ` Satyam Sharma
2007-08-15 23:22 ` Paul Mackerras
2007-08-16 0:26 ` Christoph Lameter
2007-08-16 0:34 ` Paul Mackerras
2007-08-16 0:40 ` Christoph Lameter [this message]
2007-08-16 0:39 ` Paul E. McKenney
2007-08-16 0:42 ` Christoph Lameter
2007-08-16 0:53 ` Paul E. McKenney
2007-08-16 0:59 ` Christoph Lameter
2007-08-16 1:14 ` Paul E. McKenney
2007-08-16 1:41 ` Christoph Lameter
2007-08-16 2:15 ` Satyam Sharma
2007-08-16 2:08 ` Herbert Xu
2007-08-16 2:18 ` Christoph Lameter
2007-08-16 3:23 ` Paul Mackerras
2007-08-16 3:33 ` Herbert Xu
2007-08-16 3:48 ` Paul Mackerras
2007-08-16 4:03 ` Herbert Xu
2007-08-16 4:34 ` Paul Mackerras
2007-08-16 5:37 ` Herbert Xu
2007-08-16 6:00 ` Paul Mackerras
2007-08-16 18:50 ` Christoph Lameter
2007-08-16 18:48 ` Christoph Lameter
2007-08-16 19:44 ` Segher Boessenkool
2007-08-16 2:18 ` Chris Friesen
2007-08-16 2:32 ` Paul E. McKenney
2007-08-16 1:51 ` Paul Mackerras
2007-08-16 2:00 ` Herbert Xu
2007-08-16 2:05 ` Paul Mackerras
2007-08-16 2:11 ` Herbert Xu
2007-08-16 2:35 ` Paul E. McKenney
2007-08-16 3:15 ` Paul Mackerras
2007-08-16 3:43 ` Herbert Xu
2007-08-16 2:15 ` Christoph Lameter
2007-08-16 2:17 ` Christoph Lameter
2007-08-16 2:33 ` Satyam Sharma
2007-08-16 3:01 ` Satyam Sharma
2007-08-16 4:11 ` Paul Mackerras
2007-08-16 5:39 ` Herbert Xu
2007-08-16 6:56 ` Paul Mackerras
2007-08-16 7:09 ` Herbert Xu
2007-08-16 8:06 ` Stefan Richter
2007-08-16 8:10 ` Herbert Xu
2007-08-16 9:54 ` Stefan Richter
2007-08-16 10:31 ` Stefan Richter
2007-08-16 10:42 ` Herbert Xu
2007-08-16 16:34 ` Paul E. McKenney
2007-08-16 23:59 ` Herbert Xu
2007-08-17 1:01 ` Paul E. McKenney
2007-08-17 7:39 ` Satyam Sharma
2007-08-17 14:31 ` Paul E. McKenney
2007-08-17 18:31 ` Satyam Sharma
2007-08-17 18:56 ` Paul E. McKenney
2007-08-17 3:15 ` Nick Piggin
2007-08-17 4:02 ` Paul Mackerras
2007-08-17 4:39 ` Nick Piggin
2007-08-17 7:25 ` Stefan Richter
2007-08-17 8:06 ` Nick Piggin
2007-08-17 8:58 ` Satyam Sharma
2007-08-17 9:15 ` Nick Piggin
2007-08-17 10:03 ` Satyam Sharma
2007-08-17 11:50 ` Nick Piggin
2007-08-17 12:50 ` Satyam Sharma
2007-08-17 12:56 ` Nick Piggin
2007-08-17 12:56 ` Nick Piggin
2007-08-18 2:15 ` Satyam Sharma
2007-08-17 10:48 ` Stefan Richter
2007-08-17 10:58 ` Stefan Richter
2007-08-18 14:35 ` LDD3 pitfalls (was Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures) Stefan Richter
2007-08-20 13:28 ` Chris Snook
2007-08-17 22:14 ` [PATCH 0/24] make atomic_read() behave consistently across all architectures Segher Boessenkool
2007-08-17 5:04 ` Paul Mackerras
2007-08-16 10:35 ` Herbert Xu
2007-08-16 19:48 ` Chris Snook
2007-08-17 0:02 ` Herbert Xu
2007-08-17 2:04 ` Chris Snook
2007-08-17 2:13 ` Herbert Xu
2007-08-17 2:31 ` Nick Piggin
2007-08-17 5:09 ` Paul Mackerras
2007-08-17 5:32 ` Herbert Xu
2007-08-17 5:41 ` Paul Mackerras
2007-08-17 8:28 ` Satyam Sharma
2007-08-16 14:48 ` Ilpo Järvinen
2007-08-16 16:19 ` Stefan Richter
2007-08-16 19:55 ` Chris Snook
2007-08-16 20:20 ` Christoph Lameter
2007-08-17 1:02 ` Paul E. McKenney
2007-08-17 1:28 ` Herbert Xu
2007-08-17 5:07 ` Paul E. McKenney
2007-08-17 2:16 ` Paul Mackerras
2007-08-17 3:03 ` Linus Torvalds
2007-08-17 3:43 ` Paul Mackerras
2007-08-17 3:53 ` Herbert Xu
2007-08-17 6:26 ` Satyam Sharma
2007-08-17 8:38 ` Nick Piggin
2007-08-17 9:14 ` Satyam Sharma
2007-08-17 9:31 ` Nick Piggin
2007-08-17 10:55 ` Satyam Sharma
2007-08-17 12:39 ` Nick Piggin
2007-08-17 12:39 ` Nick Piggin
2007-08-17 13:36 ` Satyam Sharma
2007-08-17 16:48 ` Linus Torvalds
2007-08-17 18:50 ` Chris Friesen
2007-08-17 18:50 ` Chris Friesen
2007-08-17 18:54 ` Arjan van de Ven
2007-08-17 19:49 ` Paul E. McKenney
2007-08-17 19:49 ` Arjan van de Ven
2007-08-17 20:12 ` Paul E. McKenney
2007-08-17 19:08 ` Linus Torvalds
2007-08-20 13:15 ` Chris Snook
2007-08-20 13:15 ` Chris Snook
2007-08-20 13:32 ` Herbert Xu
2007-08-20 13:38 ` Chris Snook
2007-08-20 22:07 ` Segher Boessenkool
2007-08-21 5:46 ` Linus Torvalds
2007-08-21 7:04 ` David Miller
2007-08-21 13:50 ` Chris Snook
2007-08-21 14:59 ` Segher Boessenkool
2007-08-21 16:31 ` Satyam Sharma
2007-08-21 16:43 ` Linus Torvalds
2007-09-09 18:02 ` Denys Vlasenko
2007-09-09 18:18 ` Arjan van de Ven
2007-09-10 10:56 ` Denys Vlasenko
2007-09-10 11:15 ` Herbert Xu
2007-09-10 12:22 ` Kyle Moffett
2007-09-10 12:22 ` Kyle Moffett
2007-09-10 13:38 ` Denys Vlasenko
2007-09-10 13:38 ` Denys Vlasenko
2007-09-10 14:16 ` Denys Vlasenko
2007-09-10 14:16 ` Denys Vlasenko
2007-09-10 15:09 ` Linus Torvalds
2007-09-10 16:46 ` Denys Vlasenko
2007-09-10 19:59 ` Kyle Moffett
2007-09-10 19:59 ` Kyle Moffett
2007-09-10 18:59 ` Christoph Lameter
2007-09-10 23:19 ` [PATCH] Document non-semantics of atomic_read() and atomic_set() Chris Snook
2007-09-10 23:19 ` Chris Snook
2007-09-10 23:44 ` Paul E. McKenney
2007-09-10 23:44 ` Paul E. McKenney
2007-09-11 19:35 ` Christoph Lameter
2007-09-11 19:35 ` Christoph Lameter
2007-09-10 14:51 ` [PATCH 0/24] make atomic_read() behave consistently across all architectures Arjan van de Ven
2007-09-10 14:38 ` Denys Vlasenko
2007-09-10 17:02 ` Arjan van de Ven
2007-08-17 11:08 ` Stefan Richter
2007-08-17 22:09 ` Segher Boessenkool
2007-08-17 22:09 ` Segher Boessenkool
2007-08-17 17:41 ` Segher Boessenkool
2007-08-17 18:38 ` Satyam Sharma
2007-08-17 23:17 ` Segher Boessenkool
2007-08-17 23:17 ` Segher Boessenkool
2007-08-17 23:55 ` Satyam Sharma
2007-08-18 0:04 ` Segher Boessenkool
2007-08-18 0:04 ` Segher Boessenkool
2007-08-18 1:56 ` Satyam Sharma
2007-08-18 2:15 ` Segher Boessenkool
2007-08-18 2:15 ` Segher Boessenkool
2007-08-18 3:33 ` Satyam Sharma
2007-08-18 5:18 ` Segher Boessenkool
2007-08-18 5:18 ` Segher Boessenkool
2007-08-18 13:20 ` Satyam Sharma
2007-09-10 18:59 ` Christoph Lameter
2007-09-10 20:54 ` Paul E. McKenney
2007-09-10 21:36 ` Christoph Lameter
2007-09-10 21:50 ` Paul E. McKenney
2007-09-11 2:27 ` Segher Boessenkool
2007-09-11 2:27 ` Segher Boessenkool
2007-08-16 21:08 ` Luck, Tony
2007-08-16 21:08 ` Luck, Tony
2007-08-16 19:55 ` Chris Snook
2007-08-16 18:54 ` Christoph Lameter
2007-08-16 20:07 ` Paul E. McKenney
2007-08-16 3:05 ` Paul Mackerras
2007-08-16 19:39 ` Segher Boessenkool
2007-08-16 2:07 ` Segher Boessenkool
2007-08-24 12:50 ` Denys Vlasenko
2007-08-24 17:15 ` Christoph Lameter
2007-08-24 20:21 ` Denys Vlasenko
2007-08-16 3:37 ` Bill Fink
2007-08-16 5:20 ` Satyam Sharma
2007-08-16 5:57 ` Satyam Sharma
2007-08-16 9:25 ` Satyam Sharma
2007-08-16 21:00 ` Segher Boessenkool
2007-08-17 4:32 ` Satyam Sharma
2007-08-17 22:38 ` Segher Boessenkool
2007-08-18 14:42 ` Satyam Sharma
2007-08-16 20:50 ` Segher Boessenkool
2007-08-16 22:40 ` David Schwartz
2007-08-17 4:36 ` Satyam Sharma
2007-08-17 4:24 ` Satyam Sharma
2007-08-17 22:34 ` Segher Boessenkool
2007-08-15 19:59 ` Christoph Lameter
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