lockd: Add helper to sanity check incoming NOTIFY requests

[safe/jmp/linux-2.6] / kernel / Kconfig.preempt

diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt
index 587328b..9fdba03 100644 (file)
--- a/kernel/Kconfig.preempt
+++ b/kernel/Kconfig.preempt
@@ -1,24 +1,79 @@
 
-config PREEMPT
-       bool "Preemptible Kernel"
+choice
+       prompt "Preemption Model"
+       default PREEMPT_NONE
+
+config PREEMPT_NONE
+       bool "No Forced Preemption (Server)"
+       help
+         This is the traditional Linux preemption model, geared towards
+         throughput. It will still provide good latencies most of the
+         time, but there are no guarantees and occasional longer delays
+         are possible.
+
+         Select this option if you are building a kernel for a server or
+         scientific/computation system, or if you want to maximize the
+         raw processing power of the kernel, irrespective of scheduling
+         latencies.
+
+config PREEMPT_VOLUNTARY
+       bool "Voluntary Kernel Preemption (Desktop)"
        help
-         This option reduces the latency of the kernel when reacting to
-         real-time or interactive events by allowing a low priority process to
-         be preempted even if it is in kernel mode executing a system call.
-         This allows applications to run more reliably even when the system is
+         This option reduces the latency of the kernel by adding more
+         "explicit preemption points" to the kernel code. These new
+         preemption points have been selected to reduce the maximum
+         latency of rescheduling, providing faster application reactions,
+         at the cost of slightly lower throughput.
+
+         This allows reaction to interactive events by allowing a
+         low priority process to voluntarily preempt itself even if it
+         is in kernel mode executing a system call. This allows
+         applications to run more 'smoothly' even when the system is
          under load.
 
-         Say Y here if you are building a kernel for a desktop, embedded
-         or real-time system.  Say N if you are unsure.
+         Select this if you are building a kernel for a desktop system.
+
+config PREEMPT
+       bool "Preemptible Kernel (Low-Latency Desktop)"
+       help
+         This option reduces the latency of the kernel by making
+         all kernel code (that is not executing in a critical section)
+         preemptible.  This allows reaction to interactive events by
+         permitting a low priority process to be preempted involuntarily
+         even if it is in kernel mode executing a system call and would
+         otherwise not be about to reach a natural preemption point.
+         This allows applications to run more 'smoothly' even when the
+         system is under load, at the cost of slightly lower throughput
+         and a slight runtime overhead to kernel code.
+
+         Select this if you are building a kernel for a desktop or
+         embedded system with latency requirements in the milliseconds
+         range.
 
-config PREEMPT_BKL
-       bool "Preempt The Big Kernel Lock"
+endchoice
+
+config PREEMPT_RCU
+       bool "Preemptible RCU"
        depends on PREEMPT
-       default y
+       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 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.