Merge branch 'for-3.18-fixes' of git://

Pull percpu fix from Tejun Heo:
 "This contains one patch to fix a race condition which can lead to
  percpu_ref using a percpu pointer which is corrupted with a set DEAD
  bit.  The bug was introduced while separating out the ATOMIC mode flag
  from the DEAD flag.  The fix is pretty straight forward.

  I just committed the patch to the percpu tree but am sending out the
  pull request early as I'll be on vacation for a week.  The patch
  should be fairly safe and while the latency will be higher I'll be
  checking emails"

* 'for-3.18-fixes' of git://
  percpu-ref: fix DEAD flag contamination of percpu pointer
diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h
index d5c89e0..51ce60c 100644
--- a/include/linux/percpu-refcount.h
+++ b/include/linux/percpu-refcount.h
@@ -133,7 +133,13 @@
 	/* paired with smp_store_release() in percpu_ref_reinit() */
-	if (unlikely(percpu_ptr & __PERCPU_REF_ATOMIC))
+	/*
+	 * Theoretically, the following could test just ATOMIC; however,
+	 * then we'd have to mask off DEAD separately as DEAD may be
+	 * visible without ATOMIC if we race with percpu_ref_kill().  DEAD
+	 * implies ATOMIC anyway.  Test them together.
+	 */
+	if (unlikely(percpu_ptr & __PERCPU_REF_ATOMIC_DEAD))
 		return false;
 	*percpu_countp = (unsigned long __percpu *)percpu_ptr;