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

Pull WW mutex support from Ingo Molnar:
 "This tree adds support for wound/wait style locks, which the graphics
  guys would like to make use of in the TTM graphics subsystem.

  Wound/wait mutexes are used when other multiple lock acquisitions of a
  similar type can be done in an arbitrary order.  The deadlock handling
  used here is called wait/wound in the RDBMS literature: The older
  tasks waits until it can acquire the contended lock.  The younger
  tasks needs to back off and drop all the locks it is currently
  holding, ie the younger task is wounded.

  See this LWN.net description of W/W mutexes:

     https://lwn.net/Articles/548909/

  The comments there outline specific usecases for this facility (which
  have already been implemented for the DRM tree).

  Also see Documentation/ww-mutex-design.txt for more details"

* 'core-mutexes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  locking-selftests: Handle unexpected failures more strictly
  mutex: Add more w/w tests to test EDEADLK path handling
  mutex: Add more tests to lib/locking-selftest.c
  mutex: Add w/w tests to lib/locking-selftest.c
  mutex: Add w/w mutex slowpath debugging
  mutex: Add support for wound/wait style locks
  arch: Make __mutex_fastpath_lock_retval return whether fastpath succeeded or not

2 files changed, 8 insertions, 14 deletions

diff --git a/arch/x86/include/asm/mutex_32.h b/arch/x86/include/asm/mutex_32.h
index 03f90c8a5a7c..0208c3c2cbc6 100644
--- a/arch/x86/include/asm/mutex_32.h
+++ b/arch/x86/include/asm/mutex_32.h
@@ -42,17 +42,14 @@ do {								\
  *  __mutex_fastpath_lock_retval - try to take the lock by moving the count
  *                                 from 1 to a 0 value
  *  @count: pointer of type atomic_t
- *  @fail_fn: function to call if the original value was not 1
  *
- * Change the count from 1 to a value lower than 1, and call <fail_fn> if it
- * wasn't 1 originally. This function returns 0 if the fastpath succeeds,
- * or anything the slow path function returns
+ * Change the count from 1 to a value lower than 1. This function returns 0
+ * if the fastpath succeeds, or -1 otherwise.
  */
-static inline int __mutex_fastpath_lock_retval(atomic_t *count,
-					       int (*fail_fn)(atomic_t *))
+static inline int __mutex_fastpath_lock_retval(atomic_t *count)
 {
 	if (unlikely(atomic_dec_return(count) < 0))
-		return fail_fn(count);
+		return -1;
 	else
 		return 0;
 }
diff --git a/arch/x86/include/asm/mutex_64.h b/arch/x86/include/asm/mutex_64.h
index 68a87b0f8e29..2c543fff241b 100644
--- a/arch/x86/include/asm/mutex_64.h
+++ b/arch/x86/include/asm/mutex_64.h
@@ -37,17 +37,14 @@ do {								\
  *  __mutex_fastpath_lock_retval - try to take the lock by moving the count
  *                                 from 1 to a 0 value
  *  @count: pointer of type atomic_t
- *  @fail_fn: function to call if the original value was not 1
  *
- * Change the count from 1 to a value lower than 1, and call <fail_fn> if
- * it wasn't 1 originally. This function returns 0 if the fastpath succeeds,
- * or anything the slow path function returns
+ * Change the count from 1 to a value lower than 1. This function returns 0
+ * if the fastpath succeeds, or -1 otherwise.
  */
-static inline int __mutex_fastpath_lock_retval(atomic_t *count,
-					       int (*fail_fn)(atomic_t *))
+static inline int __mutex_fastpath_lock_retval(atomic_t *count)
 {
 	if (unlikely(atomic_dec_return(count) < 0))
-		return fail_fn(count);
+		return -1;
 	else
 		return 0;
 }