linux-kernel - Re: [RELEASE] Userspace RCU 0.3.0

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Message-ID: <20091103155028.GC6726@linux.vnet.ibm.com>
Date:	Tue, 3 Nov 2009 07:50:28 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
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: [RELEASE] Userspace RCU 0.3.0

On Tue, Nov 03, 2009 at 10:02:34AM -0500, Mathieu Desnoyers wrote:
> Hi everyone,
> 
> I released userspace RCU 0.3.0, which includes a small API change for
> the "deferred work" interface. After discussion with Paul, I decided to
> drop the support for call_rcu() and only provide defer_rcu(), to make
> sure I don't provide an API with the same name as the kernel RCU but
> with different arguments and semantic. It will generate the following
> linker error if used:
> 
> file.c:240: undefined reference to 
>    `__error_call_rcu_not_implemented_please_use_defer_rcu'
> 
> Note that defer_rcu() should *not* be used in RCU read-side C.S.,
> because it calls synchronize_rcu() if the queue is full. This is a major
> distinction from call_rcu(). (note to self: eventually we should add
> some self-check code to detect defer_rcu() nested within RCU read-side
> C.S.).
> 
> I plan to eventually implement a proper call_rcu() within the userspace
> RCU library. It's not, however, a short-term need for me at the moment.

I can tell that we need to get you going on some real-time work.  ;-)

(Sorry, but I really couldn't resist!)

							Thanx, Paul
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