From: Stephen Hemminger <shemminger@osdl.org>
To: David Howells <dhowells@cambridge.redhat.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>,
William Lee Irwin III <wli@holomorphy.com>,
"Van Maren, Kevin" <kevin.vanmaren@unisys.com>,
linux-ia64@linuxia64.org,
Linux Kernel List <linux-kernel@vger.kernel.org>,
rusty@rustcorp.com.au, dhowells@redhat.com, mingo@elte.hu,
Linus Torvalds <torvalds@transmeta.com>
Subject: Re: [Linux-ia64] reader-writer livelock problem
Date: 08 Nov 2002 09:55:39 -0800 [thread overview]
Message-ID: <1036778139.20416.197.camel@dell_ss3.pdx.osdl.net> (raw)
In-Reply-To: <18894.1036776883@warthog.cambridge.redhat.com>
On Fri, 2002-11-08 at 09:34, David Howells wrote:
>
> > The normal way of solving this fairness problem is to make pending write
> > locks block read lock attempts, so that the reader count is guaranteed
> > to drop to zero as read locks are released. I haven't looked at the
> > Linux implementation of rwlocks, so I don't know how hard this is to
> > do. Or perhaps there's some other reason for not implementing it this
> > way?
>
> Actually implementing a fair spinlocks and fair rwlocks on the x86 arch are
> very easy (at least, if you have XADD it is). Any arch which has CMPXCHG can
> also do it, just not so easily.
>
> I've attached an implementation of a fair spinlock and an implementation of a
> fair rwlock (which can be compiled and played with in u-space).
>
> David
There are a selection of similar algorithms here:
http://www.cs.rochester.edu/u/scott/synchronization/pseudocode/rw.html#s_f
How does yours compare?
next prev parent reply other threads:[~2002-11-08 17:49 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <3FAD1088D4556046AEC48D80B47B478C0101F4E7@usslc-exch-4.slc.unisys.com>
2002-11-08 3:51 ` [Linux-ia64] reader-writer livelock problem William Lee Irwin III
2002-11-08 17:13 ` Jeremy Fitzhardinge
2002-11-08 17:25 ` Linus Torvalds
2002-11-08 17:28 ` Linus Torvalds
2002-11-08 17:38 ` Jeremy Fitzhardinge
2002-11-08 17:43 ` David Howells
2002-11-08 17:57 ` Linus Torvalds
2002-11-09 2:48 ` Rusty Russell
2002-11-09 4:36 ` William Lee Irwin III
[not found] ` <3DCFDAE9.6D359448@email.mot.com>
2002-11-11 19:22 ` David Mosberger
2002-11-12 1:39 ` your mail Rik van Riel
2002-11-08 17:34 ` [Linux-ia64] reader-writer livelock problem David Howells
2002-11-08 17:54 ` David Howells
2002-11-08 17:55 ` Stephen Hemminger [this message]
2002-11-08 17:41 Van Maren, Kevin
2002-11-08 17:52 ` Matthew Wilcox
2002-11-08 18:05 Van Maren, Kevin
2002-11-08 19:19 ` Matthew Wilcox
2002-11-08 19:26 ` David Mosberger
2002-11-08 20:17 Van Maren, Kevin
2002-11-08 20:39 ` Matthew Wilcox
2002-11-08 20:24 Van Maren, Kevin
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