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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2008-03-10 11:43:57 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2008-03-10 18:01:20 -0700 |
| commit | 21bbb39c376ce6beeeb549d155f0d53dc76ed000 (patch) | |
| tree | 762d0ae6d1cd88aaa231739c3e88437e52ffa387 /init | |
| parent | f47831fabaf0206abc56ee5a33fd006fe29b6dc6 (diff) | |
| download | op-kernel-dev-21bbb39c376ce6beeeb549d155f0d53dc76ed000.zip op-kernel-dev-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 'init')
| -rw-r--r-- | init/Kconfig | 34 |
1 files changed, 3 insertions, 31 deletions
diff --git a/init/Kconfig b/init/Kconfig index 074ac97..a97924b 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -865,38 +865,10 @@ 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. - - 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. |
