From: Chris Snook <csnook@redhat.com>
To: Stefan Richter <stefanr@s5r6.in-berlin.de>
Cc: Jonathan Corbet <corbet@lwn.net>,
Greg Kroah-Hartman <gregkh@suse.de>,
Nick Piggin <nickpiggin@yahoo.com.au>,
paulmck@linux.vnet.ibm.com,
Herbert Xu <herbert@gondor.apana.org.au>,
Paul Mackerras <paulus@samba.org>,
Satyam Sharma <satyam@infradead.org>,
Christoph Lameter <clameter@sgi.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
Subject: Re: LDD3 pitfalls (was Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures)
Date: Mon, 20 Aug 2007 09:28:05 -0400 [thread overview]
Message-ID: <46C996E5.90503@redhat.com> (raw)
In-Reply-To: <46C703C9.9060507@s5r6.in-berlin.de>
Stefan Richter wrote:
> Nick Piggin wrote:
>> Stefan Richter wrote:
>>> Nick Piggin wrote:
>>>
>>>> I don't know why people would assume volatile of atomics. AFAIK, most
>>>> of the documentation is pretty clear that all the atomic stuff can be
>>>> reordered etc. except for those that modify and return a value.
>>>
>>> Which documentation is there?
>> Documentation/atomic_ops.txt
>>
>>
>>> For driver authors, there is LDD3. It doesn't specifically cover
>>> effects of optimization on accesses to atomic_t.
>>>
>>> For architecture port authors, there is Documentation/atomic_ops.txt.
>>> Driver authors also can learn something from that document, as it
>>> indirectly documents the atomic_t and bitops APIs.
>>>
>> "Semantics and Behavior of Atomic and Bitmask Operations" is
>> pretty direct :)
>>
>> Sure, it says that it's for arch maintainers, but there is no
>> reason why users can't make use of it.
>
>
> Note, LDD3 page 238 says: "It is worth noting that most of the other
> kernel primitives dealing with synchronization, such as spinlock and
> atomic_t operations, also function as memory barriers."
>
> I don't know about Linux 2.6.10 against which LDD3 was written, but
> currently only _some_ atomic_t operations function as memory barriers.
>
> Besides, judging from some posts in this thread, saying that atomic_t
> operations dealt with synchronization may not be entirely precise.
atomic_t is often used as the basis for implementing more sophisticated
synchronization mechanisms, such as rwlocks. Whether or not they are designed
for that purpose, the atomic_* operations are de facto synchronization primitives.
-- Chris
next prev parent reply other threads:[~2007-08-20 13:29 UTC|newest]
Thread overview: 311+ 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 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 0:32 ` 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 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
2007-08-15 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
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
2007-08-18 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 [this message]
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 13:36 ` Satyam Sharma
2007-08-17 16:48 ` Linus Torvalds
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 13:32 ` 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 13:38 ` 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 18:59 ` Christoph Lameter
2007-09-10 23:19 ` [PATCH] Document non-semantics of atomic_read() and atomic_set() Chris Snook
2007-09-10 23:44 ` Paul E. McKenney
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 17:41 ` Segher Boessenkool
2007-08-17 18:38 ` Satyam Sharma
2007-08-17 23:17 ` Segher Boessenkool
2007-08-17 23:55 ` Satyam Sharma
2007-08-18 0:04 ` Segher Boessenkool
2007-08-18 1:56 ` Satyam Sharma
2007-08-18 2:15 ` Segher Boessenkool
2007-08-18 3:33 ` Satyam Sharma
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
2007-08-16 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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