linux-kernel - Re: Userspace RCU 0.2.3

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Date:	Wed, 14 Oct 2009 22:39:25 -0400
From:	Mathieu Desnoyers <compudj@...stal.dyndns.org>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	Josh Triplett <josh@...htriplett.org>,
	Jon Bernard <jbernard@...ian.org>,
	Jan Blunck <jblunck@...e.de>,
	Pierre Habouzit <madcoder@...ian.org>,
	Steven Munroe <munroesj@...ux.vnet.ibm.com>,
	Bert Wesarg <bert.wesarg@...glemail.com>,
	Pierre-Marc Fournier <pierre-marc.fournier@...ymtl.ca>,
	ltt-dev@...ts.casi.polymtl.ca, rp@...s.cs.pdx.edu,
	linux-kernel@...r.kernel.org
Subject: Re: Userspace RCU 0.2.3

* Paul E. McKenney (paulmck@...ux.vnet.ibm.com) wrote:
> On Wed, Oct 14, 2009 at 06:36:57PM -0400, Mathieu Desnoyers wrote:
> > Hi,
> > 
> > I just released lib urcu 0.2.3, which is now using autotools. I also
> > integrated automatic architecture detection for old 386 which lack
> > cmpxchg (using a fall-back if necessary). I also use a lock; addl
> > instead of mfence on x86-32 to support a larger variety of older Intel
> > CPUs.
> 
> !!!
> 
> Is there anyone on these lists other than me who has actually used an
> SMP 80386-based system?

SMP 386, ugh, no. But UP 386 yes (at least me). :)

It will become important as the library gets integrated in
distributions.

> 
> Either way, much appreciated for old time's sake.  The things we used
> to do to avoid the need for cmpxchg!  ;-)

In this case I disable signals and take a mutex around the cmpxchg. It's
really a best effort. Should be fine on UP 386, but not so much on SMP
386, as mixing it with assign/xchg pointer could lead to races. I'm not
sure it's worth trying to support 386 SMP though.

Mathieu


> 
> 							Thanx, Paul
> 
> > The build system detects if NR_futex is available in the system
> > headers. It falls back on a more portable alternative if they are not
> > available.
> > 
> > There are also new configuration modes to ./configure for UP-only
> > systems.
> > 
> > As always, the tarballs are available at http://www.lttng.org/urcu
> > 
> > Mathieu
> > 
> > -- 
> > Mathieu Desnoyers
> > OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
> 

-- 
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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