[GIT PULL] core fixes

Ingo Molnar
2010-08-24T19:02:09Z

Linus,

Please pull the latest core-fixes-for-linus git tree from:

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

This contains the mutex optimistic spinning fix from Tim Chen. It is not
a regression fix per se - but the improvement is significant enough (and
the patch is simple enough as well) to not let this sit for yet another
cycle.

Thanks,

Ingo

------------------>
Tim Chen (1):
mutex: Improve the scalability of optimistic spinning

kernel/sched.c | 10 +++++++++-
1 files changed, 9 insertions(+), 1 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index 41541d7..09b574e 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?