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

Pull locking fixes from Ingo Molnar:
 "Misc fixes:

   - a file-based futex fix
   - one more spin_unlock_wait() fix
   - a ww-mutex deadlock detection improvement/fix
   - and a raw_read_seqcount_latch() barrier fix"

* 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  futex: Calculate the futex key based on a tail page for file-based futexes
  locking/qspinlock: Fix spin_unlock_wait() some more
  locking/ww_mutex: Report recursive ww_mutex locking early
  locking/seqcount: Re-fix raw_read_seqcount_latch()

1 files changed, 5 insertions, 2 deletions

diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h
index 7973a821ac58..ead97654c4e9 100644
--- a/include/linux/seqlock.h
+++ b/include/linux/seqlock.h
@@ -277,7 +277,10 @@ static inline void raw_write_seqcount_barrier(seqcount_t *s)
 
 static inline int raw_read_seqcount_latch(seqcount_t *s)
 {
-	return lockless_dereference(s)->sequence;
+	int seq = READ_ONCE(s->sequence);
+	/* Pairs with the first smp_wmb() in raw_write_seqcount_latch() */
+	smp_read_barrier_depends();
+	return seq;
 }
 
 /**
@@ -331,7 +334,7 @@ static inline int raw_read_seqcount_latch(seqcount_t *s)
  *	unsigned seq, idx;
  *
  *	do {
- *		seq = lockless_dereference(latch)->seq;
+ *		seq = raw_read_seqcount_latch(&latch->seq);
  *
  *		idx = seq & 0x01;
  *		entry = data_query(latch->data[idx], ...);