From: Peter Zijlstra <peterz@infradead.org>
To: Waiman Long <waiman.long@hp.com>
Cc: Richard Henderson <rth@twiddle.net>,
Matt Turner <mattst88@gmail.com>,
Daniel J Blueman <daniel@numascale.com>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Linux Kernel <linux-kernel@vger.kernel.org>,
Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH v8 4/4] qrwlock: Use smp_store_release() in write_unlock()
Date: Tue, 14 Jan 2014 21:20:27 +0100 [thread overview]
Message-ID: <20140114202027.GN7572@laptop.programming.kicks-ass.net> (raw)
In-Reply-To: <52D58B6A.5070103@hp.com>
On Tue, Jan 14, 2014 at 02:09:30PM -0500, Waiman Long wrote:
> I would like to know if the action of writing out a byte (e.g. *byte = 0) is
> atomic in those architectures or is emulated by a compiler-generated
> software read-modify-write.
So on Alpha pre ev56 something like:
*(volatile u8 *)foo = 0;
_Should_ cause a compile error as the hardware has to do a rmw which is
not compatible with the requirements for volatile -- that said I do not
know if a compiler will actually generate this error.
I can well imagine other load-store archs suffering similar problems,
although I'm not aware of any.
next prev parent reply other threads:[~2014-01-14 20:20 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-13 2:47 [PATCH v8 4/4] qrwlock: Use smp_store_release() in write_unlock() Daniel J Blueman
2014-01-13 3:49 ` Paul E. McKenney
2014-01-13 16:41 ` Waiman Long
2014-01-14 2:28 ` Daniel J Blueman
2014-01-14 11:03 ` Peter Zijlstra
2014-01-14 15:25 ` Waiman Long
2014-01-14 17:08 ` Matt Turner
2014-01-14 18:01 ` Richard Henderson
2014-01-14 19:09 ` Waiman Long
2014-01-14 20:20 ` Peter Zijlstra [this message]
2014-01-14 23:44 ` Paul E. McKenney
2014-01-15 0:25 ` Linus Torvalds
2014-01-15 2:39 ` Paul E. McKenney
2014-01-15 8:07 ` Peter Zijlstra
2014-01-15 20:53 ` Paul E. McKenney
2014-01-15 23:21 ` Peter Zijlstra
[not found] ` <CA+55aFydYLQeBq=4AQQp_4dAnq09ocLmde1LFaXiNAJ=wJzfFA@mail.gmail.com>
2014-01-16 10:36 ` Peter Zijlstra
2014-01-18 10:01 ` Paul E. McKenney
2014-01-18 11:34 ` Peter Zijlstra
2014-01-18 12:25 ` Paul E. McKenney
2014-01-18 12:41 ` Peter Zijlstra
2014-01-18 21:22 ` Paul E. McKenney
2014-01-19 0:57 ` Linus Torvalds
2014-01-19 8:04 ` Paul E. McKenney
2014-01-19 19:56 ` Linus Torvalds
2014-01-20 0:52 ` Paul E. McKenney
2014-01-21 15:02 ` Waiman Long
2014-01-21 15:41 ` Peter Zijlstra
2014-01-21 16:16 ` Waiman Long
2014-01-15 3:08 ` Daniel J Blueman
-- strict thread matches above, loose matches on Subject: below --
2014-01-08 16:59 [PATCH v8 0/4] qrwlock: Introducing a queue read/write lock implementation Waiman Long
2014-01-08 16:59 ` [PATCH v8 4/4] qrwlock: Use smp_store_release() in write_unlock() Waiman Long
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