[ltt-dev] [RELEASE] Userspace RCU 0.3.0

Paul E. McKenney paulmck at linux.vnet.ibm.com
Tue Nov 3 10:50:28 EST 2009

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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