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 the locking subsystem in this cycle were:

   - Add the Linux Kernel Memory Consistency Model (LKMM) subsystem,
     which is an an array of tools in tools/memory-model/ that formally
     describe the Linux memory coherency model (a.k.a.
     Documentation/memory-barriers.txt), and also produce 'litmus tests'
     in form of kernel code which can be directly executed and tested.

     Here's a high level background article about an earlier version of
     this work on LWN.net:

        https://lwn.net/Articles/718628/

     The design principles:

      "There is reason to believe that Documentation/memory-barriers.txt
       could use some help, and a major purpose of this patch is to
       provide that help in the form of a design-time tool that can
       produce all valid executions of a small fragment of concurrent
       Linux-kernel code, which is called a "litmus test". This tool's
       functionality is roughly similar to a full state-space search.
       Please note that this is a design-time tool, not useful for
       regression testing. However, we hope that the underlying
       Linux-kernel memory model will be incorporated into other tools
       capable of analyzing large bodies of code for regression-testing
       purposes."

     [...]

      "A second tool is klitmus7, which converts litmus tests to
       loadable kernel modules for direct testing. As with herd7, the
       klitmus7 code is freely available from

         http://diy.inria.fr/sources/index.html

       (and via "git" at https://github.com/herd/herdtools7)"

     [...]

     Credits go to:

      "This patch was the result of a most excellent collaboration
       founded by Jade Alglave and also including Alan Stern, Andrea
       Parri, and Luc Maranget."

     ... and to the gents listed in the MAINTAINERS entry:

        LINUX KERNEL MEMORY CONSISTENCY MODEL (LKMM)
        M:      Alan Stern <stern@rowland.harvard.edu>
        M:      Andrea Parri <parri.andrea@gmail.com>
        M:      Will Deacon <will.deacon@arm.com>
        M:      Peter Zijlstra <peterz@infradead.org>
        M:      Boqun Feng <boqun.feng@gmail.com>
        M:      Nicholas Piggin <npiggin@gmail.com>
        M:      David Howells <dhowells@redhat.com>
        M:      Jade Alglave <j.alglave@ucl.ac.uk>
        M:      Luc Maranget <luc.maranget@inria.fr>
        M:      "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>

     The LKMM project already found several bugs in Linux locking
     primitives and improved the understanding and the documentation of
     the Linux memory model all around.

   - Add KASAN instrumentation to atomic APIs (Dmitry Vyukov)

   - Add RWSEM API debugging and reorganize the lock debugging Kconfig
     (Waiman Long)

   - ... misc cleanups and other smaller changes"

* 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (31 commits)
  locking/Kconfig: Restructure the lock debugging menu
  locking/Kconfig: Add LOCK_DEBUGGING_SUPPORT to make it more readable
  locking/rwsem: Add DEBUG_RWSEMS to look for lock/unlock mismatches
  lockdep: Make the lock debug output more useful
  locking/rtmutex: Handle non enqueued waiters gracefully in remove_waiter()
  locking/atomic, asm-generic, x86: Add comments for atomic instrumentation
  locking/atomic, asm-generic: Add KASAN instrumentation to atomic operations
  locking/atomic/x86: Switch atomic.h to use atomic-instrumented.h
  locking/atomic, asm-generic: Add asm-generic/atomic-instrumented.h
  locking/xchg/alpha: Remove superfluous memory barriers from the _local() variants
  tools/memory-model: Finish the removal of rb-dep, smp_read_barrier_depends(), and lockless_dereference()
  tools/memory-model: Add documentation of new litmus test
  tools/memory-model: Remove mention of docker/gentoo image
  locking/memory-barriers: De-emphasize smp_read_barrier_depends() some more
  locking/lockdep: Show unadorned pointers
  mutex: Drop linkage.h from mutex.h
  tools/memory-model: Remove rb-dep, smp_read_barrier_depends, and lockless_dereference
  tools/memory-model: Convert underscores to hyphens
  tools/memory-model: Add a S lock-based external-view litmus test
  tools/memory-model: Add required herd7 version to README file
  ...

1 files changed, 7 insertions, 1 deletions

diff --git a/kernel/locking/rwsem.h b/kernel/locking/rwsem.h
index a883b8f1fdc6..a17cba8d94bb 100644
--- a/kernel/locking/rwsem.h
+++ b/kernel/locking/rwsem.h
@@ -16,6 +16,12 @@
  */
 #define RWSEM_READER_OWNED	((struct task_struct *)1UL)
 
+#ifdef CONFIG_DEBUG_RWSEMS
+# define DEBUG_RWSEMS_WARN_ON(c)	DEBUG_LOCKS_WARN_ON(c)
+#else
+# define DEBUG_RWSEMS_WARN_ON(c)
+#endif
+
 #ifdef CONFIG_RWSEM_SPIN_ON_OWNER
 /*
  * All writes to owner are protected by WRITE_ONCE() to make sure that
@@ -41,7 +47,7 @@ static inline void rwsem_set_reader_owned(struct rw_semaphore *sem)
 	 * do a write to the rwsem cacheline when it is really necessary
 	 * to minimize cacheline contention.
 	 */
-	if (sem->owner != RWSEM_READER_OWNED)
+	if (READ_ONCE(sem->owner) != RWSEM_READER_OWNED)
 		WRITE_ONCE(sem->owner, RWSEM_READER_OWNED);
 }