On Fri, Feb 29, 2008 at 05:34:54AM +0100, Roman Zippel wrote: > Hi, > > On Thursday 13. December 2007, Gautham R Shenoy wrote: > > > diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt > > index c64ce9c..06cafcc 100644 > > --- a/kernel/Kconfig.preempt > > +++ b/kernel/Kconfig.preempt > > @@ -63,3 +63,41 @@ config PREEMPT_BKL > > Say Y here if you are building a kernel for a desktop system. > > Say N if you are unsure. > > > > +choice > > + prompt "RCU implementation type:" > > + default CLASSIC_RCU > > + > > +config CLASSIC_RCU > > + bool "Classic RCU" > > + help > > + This option selects the classic RCU implementation that is > > + designed for best read-side performance on non-realtime > > + systems. > > + > > + Say Y if you are unsure. > > + > > +config PREEMPT_RCU > > + bool "Preemptible RCU" > > + depends on PREEMPT > > + help > > + This option reduces the latency of the kernel by making certain > > + RCU sections preemptible. Normally RCU code is non-preemptible, if > > + this option is selected then read-only RCU sections become > > + preemptible. This helps latency, but may expose bugs due to > > + now-naive assumptions about each RCU read-side critical section > > + remaining on a given CPU through its execution. > > + > > + Say N if you are unsure. > > + > > +endchoice > > Why got this moved into init/Kconfig? Because there are some arches that don't have kernel/Kconfig.preempt, its earlier home. Therefore, putting it into kernel/Kconfig.preempt broke those arches' builds by supplying neither PREEMPT_RCU nor CLASSIC_RCU. > Now it's somewhere in the root menu, not really belonging to anything. Do you have a suggested location? > Also why is this a choice? Are more RCU types planned? I don't expect additional drop-in replacements for RCU, though people are certainly free to experiment if they wish. It is a choice because this gives people a very clear idea of the two options and because it makes the implementation a bit cleaner. Thanx, Paul -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
