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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2008-03-10 11:43:57 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-03-10 18:01:20 -0700
commit21bbb39c376ce6beeeb549d155f0d53dc76ed000 (patch)
tree762d0ae6d1cd88aaa231739c3e88437e52ffa387 /kernel/Kconfig.preempt
parentf47831fabaf0206abc56ee5a33fd006fe29b6dc6 (diff)
downloadlinaro-lsk-21bbb39c376ce6beeeb549d155f0d53dc76ed000.tar.gz
rcu: move PREEMPT_RCU config option back under PREEMPT
The original preemptible-RCU patch put the choice between classic and preemptible RCU into kernel/Kconfig.preempt, which resulted in build failures on machines not supporting CONFIG_PREEMPT. This choice was therefore moved to init/Kconfig, which worked, but placed the choice between classic and preemptible RCU at the top level, a very obtuse choice indeed. This patch changes from the Kconfig "choice" mechanism to a pair of booleans, only one of which (CONFIG_PREEMPT_RCU) is user-visible, and is located in kernel/Kconfig.preempt, where one would expect it to be. The other (CONFIG_CLASSIC_RCU) is in init/Kconfig so that it is available to all architectures, hopefully avoiding build breakage. Thanks to Roman Zippel for suggesting this approach. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Ingo Molnar <mingo@elte.hu> Acked-by: Steven Rostedt <rostedt@goodmis.org> Cc: Dipankar Sarma <dipankar@in.ibm.com> Cc: Josh Triplett <josh@freedesktop.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Roman Zippel <zippel@linux-m68k.org> Cc: Sam Ravnborg <sam@ravnborg.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/Kconfig.preempt')
-rw-r--r--kernel/Kconfig.preempt15
1 files changed, 15 insertions, 0 deletions
diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt
index 0669b70fa6a..9fdba03dc1f 100644
--- a/kernel/Kconfig.preempt
+++ b/kernel/Kconfig.preempt
@@ -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