Merge branch 'android-4.4-p' of https://android.googlesource.com/kernel/common into lineage-17.1-caf-msm8998

This brings LA.UM.8.4.r1-06000-8x98.0 up to date with
https://android.googlesource.com/kernel/common/ android-4.4-p at commit:
7a9986e91f909 UPSTREAM: binder: fix UAF when releasing todo list

Conflicts:
	fs/eventpoll.c

Change-Id: I77260d03cb539d7e7eefcea360aee2d59bb9e0cb

1 files changed, 9 insertions, 2 deletions

diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h
index e0582106ef4f..a10f36378417 100644
--- a/include/linux/seqlock.h
+++ b/include/linux/seqlock.h
@@ -242,6 +242,13 @@ static inline void raw_write_seqcount_end(seqcount_t *s)
  * usual consistency guarantee. It is one wmb cheaper, because we can
  * collapse the two back-to-back wmb()s.
  *
+ * Note that, writes surrounding the barrier should be declared atomic (e.g.
+ * via WRITE_ONCE): a) to ensure the writes become visible to other threads
+ * atomically, avoiding compiler optimizations; b) to document which writes are
+ * meant to propagate to the reader critical section. This is necessary because
+ * neither writes before and after the barrier are enclosed in a seq-writer
+ * critical section that would ensure readers are aware of ongoing writes.
+ *
  *      seqcount_t seq;
  *      bool X = true, Y = false;
  *
@@ -261,11 +268,11 @@ static inline void raw_write_seqcount_end(seqcount_t *s)
  *
  *      void write(void)
  *      {
- *              Y = true;
+ *              WRITE_ONCE(Y, true);
  *
  *              raw_write_seqcount_barrier(seq);
  *
- *              X = false;
+ *              WRITE_ONCE(X, false);
  *      }
  */
 static inline void raw_write_seqcount_barrier(seqcount_t *s)