Merge tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi

[karo-tx-linux.git] / init / Kconfig

diff --git a/init/Kconfig b/init/Kconfig
index a92f27da4a272ec873707bc4b7a68e46a4340b86..1d3475fc94967a58904627d80e8461a3721ddbb0 100644 (file)
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -521,11 +521,41 @@ config RCU_EXPERT
 
 config SRCU
        bool
+       default y
        help
          This option selects the sleepable version of RCU. This version
          permits arbitrary sleeping or blocking within RCU read-side critical
          sections.
 
+config CLASSIC_SRCU
+       bool "Use v4.11 classic SRCU implementation"
+       default n
+       depends on RCU_EXPERT && SRCU
+       help
+         This option selects the traditional well-tested classic SRCU
+         implementation from v4.11, as might be desired for enterprise
+         Linux distributions.  Without this option, the shiny new
+         Tiny SRCU and Tree SRCU implementations are used instead.
+         At some point, it is hoped that Tiny SRCU and Tree SRCU
+         will accumulate enough test time and confidence to allow
+         Classic SRCU to be dropped entirely.
+
+         Say Y if you need a rock-solid SRCU.
+
+         Say N if you would like help test Tree SRCU.
+
+config TINY_SRCU
+       bool
+       default y if SRCU && TINY_RCU && !CLASSIC_SRCU
+       help
+         This option selects the single-CPU non-preemptible version of SRCU.
+
+config TREE_SRCU
+       bool
+       default y if SRCU && !TINY_RCU && !CLASSIC_SRCU
+       help
+         This option selects the full-fledged version of SRCU.
+
 config TASKS_RCU
        bool
        default n
@@ -543,6 +573,9 @@ config RCU_STALL_COMMON
          the tiny variants to disable RCU CPU stall warnings, while
          making these warnings mandatory for the tree variants.
 
+config RCU_NEED_SEGCBLIST
+       def_bool ( TREE_RCU || PREEMPT_RCU || TINY_SRCU || TREE_SRCU )
+
 config CONTEXT_TRACKING
        bool
 
@@ -612,11 +645,17 @@ config RCU_FANOUT_LEAF
          initialization.  These systems tend to run CPU-bound, and thus
          are not helped by synchronized interrupts, and thus tend to
          skew them, which reduces lock contention enough that large
-         leaf-level fanouts work well.
+         leaf-level fanouts work well.  That said, setting leaf-level
+         fanout to a large number will likely cause problematic
+         lock contention on the leaf-level rcu_node structures unless
+         you boot with the skew_tick kernel parameter.
 
          Select a specific number if testing RCU itself.
 
-         Select the maximum permissible value for large systems.
+         Select the maximum permissible value for large systems, but
+         please understand that you may also need to set the skew_tick
+         kernel boot parameter to avoid contention on the rcu_node
+         structure's locks.
 
          Take the default if unsure.