Merge tag 'v4.4-rc2' into drm-intel-next-queued

Linux 4.4-rc2

Backmerge to get at

commit 1b0e3a049efe471c399674fd954500ce97438d30
Author: Imre Deak <imre.deak@intel.com>
Date:   Thu Nov 5 23:04:11 2015 +0200

    drm/i915/skl: disable display side power well support for now

so that we can proplery re-eanble skl power wells in -next.

Conflicts are just adjacent lines changed, except for intel_fbdev.c
where we need to interleave the changs. Nothing nefarious.

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

1 files changed, 15 insertions, 1 deletions

diff --git a/include/linux/types.h b/include/linux/types.h
index c314989d9158..70d8500bddf1 100644
--- a/include/linux/types.h
+++ b/include/linux/types.h
@@ -205,11 +205,25 @@ struct ustat {
  * struct callback_head - callback structure for use with RCU and task_work
  * @next: next update requests in a list
  * @func: actual update function to call after the grace period.
+ *
+ * The struct is aligned to size of pointer. On most architectures it happens
+ * naturally due ABI requirements, but some architectures (like CRIS) have
+ * weird ABI and we need to ask it explicitly.
+ *
+ * The alignment is required to guarantee that bits 0 and 1 of @next will be
+ * clear under normal conditions -- as long as we use call_rcu(),
+ * call_rcu_bh(), call_rcu_sched(), or call_srcu() to queue callback.
+ *
+ * This guarantee is important for few reasons:
+ *  - future call_rcu_lazy() will make use of lower bits in the pointer;
+ *  - the structure shares storage spacer in struct page with @compound_head,
+ *    which encode PageTail() in bit 0. The guarantee is needed to avoid
+ *    false-positive PageTail().
  */
 struct callback_head {
 	struct callback_head *next;
 	void (*func)(struct callback_head *head);
-};
+} __attribute__((aligned(sizeof(void *))));
 #define rcu_head callback_head
 
 typedef void (*rcu_callback_t)(struct rcu_head *head);