Merge branch 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  mutex: Improve the scalability of optimistic spinning

1 files changed, 9 insertions, 1 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 41541d79e3c8..09b574e7f4df 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -3865,8 +3865,16 @@ int mutex_spin_on_owner(struct mutex *lock, struct thread_info *owner)
                 /*
                  * Owner changed, break to re-assess state.
                  */
-                if (lock->owner != owner)
+                if (lock->owner != owner) {
+                        /*
+                         * If the lock has switched to a different owner,
+                         * we likely have heavy contention. Return 0 to quit
+                         * optimistic spinning and not contend further:
+                         */
+                        if (lock->owner)
+                                return 0;
                         break;
+                }
 
                 /*
                  * Is that owner really running on that cpu?