Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull RCU changes from Ingo Molnar:
 "The main changes in this cycle were:

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

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

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

   - NO_HZ_FULL_SYSIDLE fixes.

   - tiny-RCU updates to make it more tiny.

   - documentation updates.

   - miscellaneous fixes"

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (58 commits)
  cpu: Provide smpboot_thread_init() on !CONFIG_SMP kernels as well
  cpu: Defer smpboot kthread unparking until CPU known to scheduler
  rcu: Associate quiescent-state reports with grace period
  rcu: Yet another fix for preemption and CPU hotplug
  rcu: Add diagnostics to grace-period cleanup
  rcutorture: Default to grace-period-initialization delays
  rcu: Handle outgoing CPUs on exit from idle loop
  cpu: Make CPU-offline idle-loop transition point more precise
  rcu: Eliminate ->onoff_mutex from rcu_node structure
  rcu: Process offlining and onlining only at grace-period start
  rcu: Move rcu_report_unblock_qs_rnp() to common code
  rcu: Rework preemptible expedited bitmask handling
  rcu: Remove event tracing from rcu_cpu_notify(), used by offline CPUs
  rcutorture: Enable slow grace-period initializations
  rcu: Provide diagnostic option to slow down grace-period initialization
  rcu: Detect stalls caused by failure to propagate up rcu_node tree
  rcu: Eliminate empty HOTPLUG_CPU ifdef
  rcu: Simplify sync_rcu_preempt_exp_init()
  rcu: Put all orphan-callback-related code under same comment
  rcu: Consolidate offline-CPU callback initialization
  ...

1 files changed, 25 insertions, 10 deletions

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 36b6fa88ce5b..93967e634a1e 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1193,16 +1193,7 @@ 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"
@@ -1270,6 +1261,30 @@ 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