Merge branch 'for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu

Pull RCU updates from Paul E. McKenney:

  - Documentation updates.

  - Changes permitting use of call_rcu() and friends very early in
    boot, for example, before rcu_init() is invoked.

  - Miscellaneous fixes.

  - Add in-kernel API to enable and disable expediting of normal RCU
    grace periods.

  - Improve RCU's handling of (hotplug-) outgoing CPUs.

    Note: ARM support is lagging a bit here, and these improved
    diagnostics might generate (harmless) splats.

  - NO_HZ_FULL_SYSIDLE fixes.

  - Tiny RCU updates to make it more tiny.

Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 25 insertions, 10 deletions

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index c5cefb3c009c..1ad74c0df01f 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1180,16 +1180,7 @@ config DEBUG_CREDENTIALS
 menu "RCU Debugging"
 
 config PROVE_RCU
-	bool "RCU debugging: prove RCU correctness"
-	depends on PROVE_LOCKING
-	default n
-	help
-	 This feature enables lockdep extensions that check for correct
-	 use of RCU APIs.  This is currently under development.  Say Y
-	 if you want to debug RCU usage or help work on the PROVE_RCU
-	 feature.
-
-	 Say N if you are unsure.
+	def_bool PROVE_LOCKING
 
 config PROVE_RCU_REPEATEDLY
 	bool "RCU debugging: don't disable PROVE_RCU on first splat"
@@ -1257,6 +1248,30 @@ config RCU_TORTURE_TEST_RUNNABLE
 	  Say N here if you want the RCU torture tests to start only
 	  after being manually enabled via /proc.
 
+config RCU_TORTURE_TEST_SLOW_INIT
+	bool "Slow down RCU grace-period initialization to expose races"
+	depends on RCU_TORTURE_TEST
+	help
+	  This option makes grace-period initialization block for a
+	  few jiffies between initializing each pair of consecutive
+	  rcu_node structures.	This helps to expose races involving
+	  grace-period initialization, in other words, it makes your
+	  kernel less stable.  It can also greatly increase grace-period
+	  latency, especially on systems with large numbers of CPUs.
+	  This is useful when torture-testing RCU, but in almost no
+	  other circumstance.
+
+	  Say Y here if you want your system to crash and hang more often.
+	  Say N if you want a sane system.
+
+config RCU_TORTURE_TEST_SLOW_INIT_DELAY
+	int "How much to slow down RCU grace-period initialization"
+	range 0 5
+	default 3
+	help
+	  This option specifies the number of jiffies to wait between
+	  each rcu_node structure initialization.
+
 config RCU_CPU_STALL_TIMEOUT
 	int "RCU CPU stall timeout in seconds"
 	depends on RCU_STALL_COMMON