On Sat, 1 Mar 2008, Paul E. McKenney wrote: > Is this what you had in mind? I don't have any way to test on a > system not supporting CONFIG_PREEMPT, but seems to work on x86. > > Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> > --- > > init/Kconfig | 34 +++------------------------------- > kernel/Kconfig.preempt | 15 +++++++++++++++ > 2 files changed, 18 insertions(+), 31 deletions(-) > > diff -urpNa -X dontdiff linux-2.6.25-rc3/init/Kconfig linux-2.6.25-rc3-preempt_rcu/init/Kconfig > --- linux-2.6.25-rc3/init/Kconfig 2008-02-26 16:58:42.000000000 -0800 > +++ linux-2.6.25-rc3-preempt_rcu/init/Kconfig 2008-03-01 11:30:59.000000000 -0800 > @@ -860,38 +860,10 @@ source "block/Kconfig" > config PREEMPT_NOTIFIERS > bool > > -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" > + def_bool !PREEMPT_RCU > help > This option selects the classic RCU implementation that is > designed for best read-side performance on non-realtime > - systems. Actually Paul, you don't need to make this an "option". Simply the default if PREEMPT_RCU is not selected. In otherwords, no prompt. config CLASSIC_RCU bool depends on !PREEMPT_RCU default y Then, have the PREEMPT_RCU defined down below (as you already did), and have it be the only option. That is, you can have normal RCU or select to have PREEMPT_RCU. If the user selects PREEMPT_RCU, CLASSIC_RCU will be unselected. -- Steve > - > - 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 > + systems. Classic RCU is the default. Note that the > + PREEMPT_RCU symbol is used to select/deselect this option. > diff -urpNa -X dontdiff linux-2.6.25-rc3/kernel/Kconfig.preempt linux-2.6.25-rc3-preempt_rcu/kernel/Kconfig.preempt > --- linux-2.6.25-rc3/kernel/Kconfig.preempt 2008-02-26 16:58:42.000000000 -0800 > +++ linux-2.6.25-rc3-preempt_rcu/kernel/Kconfig.preempt 2008-03-01 11:35:39.000000000 -0800 > @@ -52,8 +52,23 @@ config PREEMPT > > endchoice > > +config PREEMPT_RCU > + bool "Preemptible RCU" > + depends on PREEMPT > + default n > + 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. > + > config RCU_TRACE > bool "Enable tracing for RCU - currently stats in debugfs" > + depends on PREEMPT_RCU > select DEBUG_FS > default y > help > -- 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
