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

Pull core locking updates from Ingo Molnar:
 "The biggest change is the MCS spinlock generalization changes from Tim
  Chen, Peter Zijlstra, Jason Low et al.  There's also lockdep
  fixes/enhancements from Oleg Nesterov, in particular a false negative
  fix related to lockdep_set_novalidate_class() usage"

* 'core-locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (22 commits)
  locking/mutex: Fix debug checks
  locking/mutexes: Add extra reschedule point
  locking/mutexes: Introduce cancelable MCS lock for adaptive spinning
  locking/mutexes: Unlock the mutex without the wait_lock
  locking/mutexes: Modify the way optimistic spinners are queued
  locking/mutexes: Return false if task need_resched() in mutex_can_spin_on_owner()
  locking: Move mcs_spinlock.h into kernel/locking/
  m68k: Skip futex_atomic_cmpxchg_inatomic() test
  futex: Allow architectures to skip futex_atomic_cmpxchg_inatomic() test
  Revert "sched/wait: Suppress Sparse 'variable shadowing' warning"
  lockdep: Change lockdep_set_novalidate_class() to use _and_name
  lockdep: Change mark_held_locks() to check hlock->check instead of lockdep_no_validate
  lockdep: Don't create the wrong dependency on hlock->check == 0
  lockdep: Make held_lock->check and "int check" argument bool
  locking/mcs: Allow architecture specific asm files to be used for contended case
  locking/mcs: Order the header files in Kbuild of each architecture in alphabetical order
  sched/wait: Suppress Sparse 'variable shadowing' warning
  hung_task/Documentation: Fix hung_task_warnings description
  locking/mcs: Allow architectures to hook in to contended paths
  locking/mcs: Micro-optimize the MCS code, add extra comments
  ...

1 files changed, 24 insertions, 13 deletions

diff --git a/kernel/futex.c b/kernel/futex.c
index 08ec814ad9d2..67dacaf93e56 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -157,7 +157,9 @@
  * enqueue.
  */
 
+#ifndef CONFIG_HAVE_FUTEX_CMPXCHG
 int __read_mostly futex_cmpxchg_enabled;
+#endif
 
 /*
  * Futex flags used to encode options to functions and preserve them across
@@ -2875,9 +2877,28 @@ SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val,
         return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
 }
 
-static int __init futex_init(void)
+static void __init futex_detect_cmpxchg(void)
 {
+#ifndef CONFIG_HAVE_FUTEX_CMPXCHG
         u32 curval;
+
+        /*
+         * This will fail and we want it. Some arch implementations do
+         * runtime detection of the futex_atomic_cmpxchg_inatomic()
+         * functionality. We want to know that before we call in any
+         * of the complex code paths. Also we want to prevent
+         * registration of robust lists in that case. NULL is
+         * guaranteed to fault and we get -EFAULT on functional
+         * implementation, the non-functional ones will return
+         * -ENOSYS.
+         */
+        if (cmpxchg_futex_value_locked(&curval, NULL, 0, 0) == -EFAULT)
+                futex_cmpxchg_enabled = 1;
+#endif
+}
+
+static int __init futex_init(void)
+{
         unsigned int futex_shift;
         unsigned long i;
 
@@ -2893,18 +2914,8 @@ static int __init futex_init(void)
                                                &futex_shift, NULL,
                                                futex_hashsize, futex_hashsize);
         futex_hashsize = 1UL << futex_shift;
-        /*
-         * This will fail and we want it. Some arch implementations do
-         * runtime detection of the futex_atomic_cmpxchg_inatomic()
-         * functionality. We want to know that before we call in any
-         * of the complex code paths. Also we want to prevent
-         * registration of robust lists in that case. NULL is
-         * guaranteed to fault and we get -EFAULT on functional
-         * implementation, the non-functional ones will return
-         * -ENOSYS.
-         */
-        if (cmpxchg_futex_value_locked(&curval, NULL, 0, 0) == -EFAULT)
-                futex_cmpxchg_enabled = 1;
+
+        futex_detect_cmpxchg();
 
         for (i = 0; i < futex_hashsize; i++) {
                 atomic_set(&futex_queues[i].waiters, 0);