Re: [PATCH 3/4 RFC] RCU: preemptible RCU

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

On Wed, Aug 08, 2007 at 11:10:32AM +0200, John Sigler wrote:
> [ Recipients list trimmed ]
> 
> Paul E. McKenney wrote:
> 
> >This patch was developed as a part of the -rt kernel development and
> >meant to provide better latencies when read-side critical sections of
> >RCU don't disable preemption.  As a consequence of keeping track of RCU
> >readers, the readers have a slight overhead (optimizations in the paper).
> >This implementation co-exists with the "classic" RCU implementations
> >and can be switched to at compiler.
> 
> I cannot parse the last sentence :-)

Oops...  :-/

> Did you mean that this new implementation can be chosen (over the 
> classic implementation) at compile-time?

Yes, via config variables.  CONFIG_CLASSIC_RCU selects the "classic"
RCU implementation, and CONFIG_PREEMPT_RCU selects the preemptible RCU.
CONFIG_PREEMPT_CPU depends on CONFIG_PREEMPT, so that you only are
permitted to specify CONFIG_PREEMPT_RT in preemptible kernels.

						Thanx, Paul