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

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

   - Implement wraparound-safe refcount_t and kref_t types based on
     generic atomic primitives (Peter Zijlstra)

   - Improve and fix the ww_mutex code (Nicolai Hähnle)

   - Add self-tests to the ww_mutex code (Chris Wilson)

   - Optimize percpu-rwsems with the 'rcuwait' mechanism (Davidlohr
     Bueso)

   - Micro-optimize the current-task logic all around the core kernel
     (Davidlohr Bueso)

   - Tidy up after recent optimizations: remove stale code and APIs,
     clean up the code (Waiman Long)

   - ... plus misc fixes, updates and cleanups"

* 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (50 commits)
  fork: Fix task_struct alignment
  locking/spinlock/debug: Remove spinlock lockup detection code
  lockdep: Fix incorrect condition to print bug msgs for MAX_LOCKDEP_CHAIN_HLOCKS
  lkdtm: Convert to refcount_t testing
  kref: Implement 'struct kref' using refcount_t
  refcount_t: Introduce a special purpose refcount type
  sched/wake_q: Clarify queue reinit comment
  sched/wait, rcuwait: Fix typo in comment
  locking/mutex: Fix lockdep_assert_held() fail
  locking/rtmutex: Flip unlikely() branch to likely() in __rt_mutex_slowlock()
  locking/rwsem: Reinit wake_q after use
  locking/rwsem: Remove unnecessary atomic_long_t casts
  jump_labels: Move header guard #endif down where it belongs
  locking/atomic, kref: Implement kref_put_lock()
  locking/ww_mutex: Turn off __must_check for now
  locking/atomic, kref: Avoid more abuse
  locking/atomic, kref: Use kref_get_unless_zero() more
  locking/atomic, kref: Kill kref_sub()
  locking/atomic, kref: Add kref_read()
  locking/atomic, kref: Add KREF_INIT()
  ...

lib/Kconfig.debug

@@ -716,6 +716,19 @@ source "lib/Kconfig.kmemcheck"
 
 source "lib/Kconfig.kasan"
 
+config DEBUG_REFCOUNT
+	bool "Verbose refcount checks"
+	help
+	  Say Y here if you want reference counters (refcount_t and kref) to
+	  generate WARNs on dubious usage. Without this refcount_t will still
+	  be a saturating counter and avoid Use-After-Free by turning it into
+	  a resource leak Denial-Of-Service.
+
+	  Use of this option will increase kernel text size but will alert the
+	  admin of potential abuse.
+
+	  If in doubt, say "N".
+
 endmenu # "Memory Debugging"
 
 config ARCH_HAS_KCOV
@@ -1166,6 +1179,18 @@ config LOCK_TORTURE_TEST
 	  Say M if you want these torture tests to build as a module.
 	  Say N if you are unsure.
 
+config WW_MUTEX_SELFTEST
+	tristate "Wait/wound mutex selftests"
+	help
+	  This option provides a kernel module that runs tests on the
+	  on the struct ww_mutex locking API.
+
+	  It is recommended to enable DEBUG_WW_MUTEX_SLOWPATH in conjunction
+	  with this test harness.
+
+	  Say M if you want these self tests to build as a module.
+	  Say N if you are unsure.
+
 endmenu # lock debugging
 
 config TRACE_IRQFLAGS