From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: Christoph Lameter <cl@linux.com>
Cc: Tejun Heo <tj@kernel.org>,
akpm@linux-foundation.org, Pekka Enberg <penberg@cs.helsinki.fi>,
linux-kernel@vger.kernel.org,
Eric Dumazet <eric.dumazet@gmail.com>,
"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [cpuops cmpxchg double V2 1/4] Generic support for this_cpu_cmpxchg_double
Date: Thu, 6 Jan 2011 16:08:46 -0500 [thread overview]
Message-ID: <20110106210846.GA3528@Krystal> (raw)
In-Reply-To: <20110106204525.222395863@linux.com>
* Christoph Lameter (cl@linux.com) wrote:
[...]
> + * cmpxchg_double replaces two adjacent scalars at once. The first two
> + * parameters are per cpu variables which have to be of the same size.
> + * A truth value is returned to indicate success or
> + * failure (since a double register result is difficult to handle).
> + * There is very limited hardware support for these operations. So only certain
> + * sizes may work.
What's the issue with returning the value read by cmpxchg_double in addition to
the boolean ? "returning" it per se might be an issue, but you could add 2 more
parameters to the macros that take the addresses of these outputs. Returning the
values read by cmpxchg instead of just the boolean result helps removing the
extra reads from cmpxchg loops, which is why I think it's a shame to just return
the boolean result.
Thoughts ?
Mathieu
--
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
next prev parent reply other threads:[~2011-01-06 21:08 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-06 20:45 [cpuops cmpxchg double V2 0/4] this_cpu_cmpxchg_double support Christoph Lameter
2011-01-06 20:45 ` [cpuops cmpxchg double V2 1/4] Generic support for this_cpu_cmpxchg_double Christoph Lameter
2011-01-06 21:08 ` Mathieu Desnoyers [this message]
2011-01-06 21:43 ` Christoph Lameter
2011-01-06 22:05 ` H. Peter Anvin
2011-01-07 15:15 ` Christoph Lameter
2011-01-07 18:04 ` Mathieu Desnoyers
2011-01-07 18:41 ` Christoph Lameter
2011-01-08 17:24 ` Tejun Heo
2011-01-09 8:33 ` Pekka Enberg
2011-01-21 7:31 ` Pekka Enberg
2011-01-21 9:26 ` Tejun Heo
2011-01-21 15:31 ` H. Peter Anvin
2011-01-21 15:48 ` Tejun Heo
2011-01-21 16:30 ` H. Peter Anvin
2011-01-21 16:34 ` Tejun Heo
2011-01-21 16:54 ` Mathieu Desnoyers
2011-01-21 17:07 ` Christoph Lameter
2011-01-21 17:50 ` Mathieu Desnoyers
2011-01-21 18:06 ` Christoph Lameter
2011-01-21 18:37 ` Mathieu Desnoyers
2011-01-21 17:08 ` Tejun Heo
2011-01-21 17:13 ` H. Peter Anvin
2011-01-21 17:19 ` Tejun Heo
2011-01-24 6:01 ` H. Peter Anvin
2011-02-25 13:09 ` Pekka Enberg
2011-02-25 13:19 ` Tejun Heo
2011-02-25 16:26 ` Christoph Lameter
2011-02-25 16:37 ` Tejun Heo
2011-02-25 16:43 ` Christoph Lameter
2011-02-25 16:38 ` Eric Dumazet
2011-02-25 16:45 ` Christoph Lameter
2011-01-21 17:24 ` Christoph Lameter
2011-01-21 17:42 ` Mathieu Desnoyers
2011-01-21 17:50 ` Christoph Lameter
2011-01-21 18:10 ` Mathieu Desnoyers
2011-01-21 18:42 ` Christoph Lameter
2011-01-21 18:31 ` H. Peter Anvin
2011-01-21 18:46 ` Christoph Lameter
2011-01-21 19:32 ` Mathieu Desnoyers
2011-01-23 18:00 ` H. Peter Anvin
2011-01-06 20:45 ` [cpuops cmpxchg double V2 2/4] x86: this_cpu_cmpxchg_double() support Christoph Lameter
2011-01-06 20:45 ` [cpuops cmpxchg double V2 3/4] slub: Get rid of slab_free_hook_irq() Christoph Lameter
2011-01-06 20:45 ` [cpuops cmpxchg double V2 4/4] Lockless (and preemptless) fastpaths for slub Christoph Lameter
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