Re: preemptible RCU bug (was Re: [git pull] scheduler changes for v2.6.25)

[Ingo Molnar <mingo@elte.hu>]

* Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote:

> > Sorry, no help available for this option yet.
> 
> Good catch!!!
> 
> This patch supplies help text for the "RCU implementation type" kernel 
> configuration choice.

thanks applied to sched.git. (see the patch below - the config option is 
in init/Kconfig in mainline, not in kernel/Kconfig.preempt)

	Ingo

------------->
Subject: RCU: add help text for "RCU implementation type"
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>

This patch supplies help text for the "RCU implementation type"
kernel configuration choice.

Reported-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

 init/Kconfig |    8 ++++++++
 1 file changed, 8 insertions(+)

Index: linux/init/Kconfig
===================================================================
--- linux.orig/init/Kconfig
+++ linux/init/Kconfig
@@ -779,6 +779,14 @@ config PREEMPT_NOTIFIERS
 choice
 	prompt "RCU implementation type:"
 	default CLASSIC_RCU
+	help
+	  This allows you to choose either the classic RCU implementation
+	  that is designed for best read-side performance on non-realtime
+	  systems, or the preemptible RCU implementation for best latency
+	  on realtime systems.  Note that some kernel preemption modes
+	  will restrict your choice.
+
+	  Select the default if you are unsure.
 
 config CLASSIC_RCU
 	bool "Classic RCU"