rcu: move PREEMPT_RCU config option back under PREEMPT

[sfrench/cifs-2.6.git] / kernel / Kconfig.preempt

diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt
index 6b066632e40c2a9f0621d487d0caf5a7700c7b41..9fdba03dc1fcd119c31274fb3590480aa1db9f05 100644 (file)
--- a/kernel/Kconfig.preempt
+++ b/kernel/Kconfig.preempt
@@ -52,17 +52,28 @@ config PREEMPT
 
 endchoice
 
-config PREEMPT_BKL
-       bool "Preempt The Big Kernel Lock"
-       depends on SMP || PREEMPT
-       default y
+config PREEMPT_RCU
+       bool "Preemptible RCU"
+       depends on PREEMPT
+       default n
        help
-         This option reduces the latency of the kernel by making the
-         big kernel lock preemptible.
+         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 Y here if you are building a kernel for a desktop system.
          Say N if you are unsure.
 
-config PREEMPT_NOTIFIERS
-       bool
+config RCU_TRACE
+       bool "Enable tracing for RCU - currently stats in debugfs"
+       depends on PREEMPT_RCU
+       select DEBUG_FS
+       default y
+       help
+         This option provides tracing in RCU which presents stats
+         in debugfs for debugging RCU implementation.
 
+         Say Y here if you want to enable RCU tracing
+         Say N if you are unsure.