tools: Update rbtree implementation

There have been a number of changes in the kernel's rbrtee
implementation, including loose lockless searching guarantees and
rb_root_cached, which later patches will use as an optimization.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/20181206191819.30182-2-dave@stgolabs.net
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

2 files changed, 94 insertions, 18 deletions

diff --git a/tools/include/linux/rbtree.h b/tools/include/linux/rbtree.h
index 112582253dd0..8e9ed4786269 100644
--- a/tools/include/linux/rbtree.h
+++ b/tools/include/linux/rbtree.h
@@ -43,13 +43,28 @@ struct rb_root {
 	struct rb_node *rb_node;
 };
 
+/*
+ * Leftmost-cached rbtrees.
+ *
+ * We do not cache the rightmost node based on footprint
+ * size vs number of potential users that could benefit
+ * from O(1) rb_last(). Just not worth it, users that want
+ * this feature can always implement the logic explicitly.
+ * Furthermore, users that want to cache both pointers may
+ * find it a bit asymmetric, but that's ok.
+ */
+struct rb_root_cached {
+	struct rb_root rb_root;
+	struct rb_node *rb_leftmost;
+};
 
 #define rb_parent(r)   ((struct rb_node *)((r)->__rb_parent_color & ~3))
 
 #define RB_ROOT	(struct rb_root) { NULL, }
+#define RB_ROOT_CACHED (struct rb_root_cached) { {NULL, }, NULL }
 #define	rb_entry(ptr, type, member) container_of(ptr, type, member)
 
-#define RB_EMPTY_ROOT(root)  ((root)->rb_node == NULL)
+#define RB_EMPTY_ROOT(root)  (READ_ONCE((root)->rb_node) == NULL)
 
 /* 'empty' nodes are nodes that are known not to be inserted in an rbtree */
 #define RB_EMPTY_NODE(node)  \
@@ -68,6 +83,12 @@ extern struct rb_node *rb_prev(const struct rb_node *);
 extern struct rb_node *rb_first(const struct rb_root *);
 extern struct rb_node *rb_last(const struct rb_root *);
 
+extern void rb_insert_color_cached(struct rb_node *,
+				   struct rb_root_cached *, bool);
+extern void rb_erase_cached(struct rb_node *node, struct rb_root_cached *);
+/* Same as rb_first(), but O(1) */
+#define rb_first_cached(root) (root)->rb_leftmost
+
 /* Postorder iteration - always visit the parent after its children */
 extern struct rb_node *rb_first_postorder(const struct rb_root *);
 extern struct rb_node *rb_next_postorder(const struct rb_node *);
@@ -75,6 +96,8 @@ extern struct rb_node *rb_next_postorder(const struct rb_node *);
 /* Fast replacement of a single node without remove/rebalance/add/rebalance */
 extern void rb_replace_node(struct rb_node *victim, struct rb_node *new,
 			    struct rb_root *root);
+extern void rb_replace_node_cached(struct rb_node *victim, struct rb_node *new,
+				   struct rb_root_cached *root);
 
 static inline void rb_link_node(struct rb_node *node, struct rb_node *parent,
 				struct rb_node **rb_link)
@@ -90,12 +113,29 @@ static inline void rb_link_node(struct rb_node *node, struct rb_node *parent,
 	   ____ptr ? rb_entry(____ptr, type, member) : NULL; \
 	})
 
-
-/*
- * Handy for checking that we are not deleting an entry that is
- * already in a list, found in block/{blk-throttle,cfq-iosched}.c,
- * probably should be moved to lib/rbtree.c...
+/**
+ * rbtree_postorder_for_each_entry_safe - iterate in post-order over rb_root of
+ * given type allowing the backing memory of @pos to be invalidated
+ *
+ * @pos:	the 'type *' to use as a loop cursor.
+ * @n:		another 'type *' to use as temporary storage
+ * @root:	'rb_root *' of the rbtree.
+ * @field:	the name of the rb_node field within 'type'.
+ *
+ * rbtree_postorder_for_each_entry_safe() provides a similar guarantee as
+ * list_for_each_entry_safe() and allows the iteration to continue independent
+ * of changes to @pos by the body of the loop.
+ *
+ * Note, however, that it cannot handle other modifications that re-order the
+ * rbtree it is iterating over. This includes calling rb_erase() on @pos, as
+ * rb_erase() may rebalance the tree, causing us to miss some nodes.
  */
+#define rbtree_postorder_for_each_entry_safe(pos, n, root, field) \
+	for (pos = rb_entry_safe(rb_first_postorder(root), typeof(*pos), field); \
+	     pos && ({ n = rb_entry_safe(rb_next_postorder(&pos->field), \
+			typeof(*pos), field); 1; }); \
+	     pos = n)
+
 static inline void rb_erase_init(struct rb_node *n, struct rb_root *root)
 {
 	rb_erase(n, root);
diff --git a/tools/include/linux/rbtree_augmented.h b/tools/include/linux/rbtree_augmented.h
index 43be941db695..d008e1404580 100644
--- a/tools/include/linux/rbtree_augmented.h
+++ b/tools/include/linux/rbtree_augmented.h
@@ -44,7 +44,9 @@ struct rb_augment_callbacks {
 	void (*rotate)(struct rb_node *old, struct rb_node *new);
 };
 
-extern void __rb_insert_augmented(struct rb_node *node, struct rb_root *root,
+extern void __rb_insert_augmented(struct rb_node *node,
+				  struct rb_root *root,
+				  bool newleft, struct rb_node **leftmost,
 	void (*augment_rotate)(struct rb_node *old, struct rb_node *new));
 /*
  * Fixup the rbtree and update the augmented information when rebalancing.
@@ -60,7 +62,16 @@ static inline void
 rb_insert_augmented(struct rb_node *node, struct rb_root *root,
 		    const struct rb_augment_callbacks *augment)
 {
-	__rb_insert_augmented(node, root, augment->rotate);
+	__rb_insert_augmented(node, root, false, NULL, augment->rotate);
+}
+
+static inline void
+rb_insert_augmented_cached(struct rb_node *node,
+			   struct rb_root_cached *root, bool newleft,
+			   const struct rb_augment_callbacks *augment)
+{
+	__rb_insert_augmented(node, &root->rb_root,
+			      newleft, &root->rb_leftmost, augment->rotate);
 }
 
 #define RB_DECLARE_CALLBACKS(rbstatic, rbname, rbstruct, rbfield,	\
@@ -93,7 +104,9 @@ rbname ## _rotate(struct rb_node *rb_old, struct rb_node *rb_new)	\
 	old->rbaugmented = rbcompute(old);				\
 }									\
 rbstatic const struct rb_augment_callbacks rbname = {			\
-	rbname ## _propagate, rbname ## _copy, rbname ## _rotate	\
+	.propagate = rbname ## _propagate,				\
+	.copy = rbname ## _copy,					\
+	.rotate = rbname ## _rotate					\
 };
 
 
@@ -126,11 +139,11 @@ __rb_change_child(struct rb_node *old, struct rb_node *new,
 {
 	if (parent) {
 		if (parent->rb_left == old)
-			parent->rb_left = new;
+			WRITE_ONCE(parent->rb_left, new);
 		else
-			parent->rb_right = new;
+			WRITE_ONCE(parent->rb_right, new);
 	} else
-		root->rb_node = new;
+		WRITE_ONCE(root->rb_node, new);
 }
 
 extern void __rb_erase_color(struct rb_node *parent, struct rb_root *root,
@@ -138,12 +151,17 @@ extern void __rb_erase_color(struct rb_node *parent, struct rb_root *root,
 
 static __always_inline struct rb_node *
 __rb_erase_augmented(struct rb_node *node, struct rb_root *root,
+		     struct rb_node **leftmost,
 		     const struct rb_augment_callbacks *augment)
 {
-	struct rb_node *child = node->rb_right, *tmp = node->rb_left;
+	struct rb_node *child = node->rb_right;
+	struct rb_node *tmp = node->rb_left;
 	struct rb_node *parent, *rebalance;
 	unsigned long pc;
 
+	if (leftmost && node == *leftmost)
+		*leftmost = rb_next(node);
+
 	if (!tmp) {
 		/*
 		 * Case 1: node to erase has no more than 1 child (easy!)
@@ -170,6 +188,7 @@ __rb_erase_augmented(struct rb_node *node, struct rb_root *root,
 		tmp = parent;
 	} else {
 		struct rb_node *successor = child, *child2;
+
 		tmp = child->rb_left;
 		if (!tmp) {
 			/*
@@ -183,6 +202,7 @@ __rb_erase_augmented(struct rb_node *node, struct rb_root *root,
 			 */
 			parent = successor;
 			child2 = successor->rb_right;
+
 			augment->copy(node, successor);
 		} else {
 			/*
@@ -204,19 +224,23 @@ __rb_erase_augmented(struct rb_node *node, struct rb_root *root,
 				successor = tmp;
 				tmp = tmp->rb_left;
 			} while (tmp);
-			parent->rb_left = child2 = successor->rb_right;
-			successor->rb_right = child;
+			child2 = successor->rb_right;
+			WRITE_ONCE(parent->rb_left, child2);
+			WRITE_ONCE(successor->rb_right, child);
 			rb_set_parent(child, successor);
+
 			augment->copy(node, successor);
 			augment->propagate(parent, successor);
 		}
 
-		successor->rb_left = tmp = node->rb_left;
+		tmp = node->rb_left;
+		WRITE_ONCE(successor->rb_left, tmp);
 		rb_set_parent(tmp, successor);
 
 		pc = node->__rb_parent_color;
 		tmp = __rb_parent(pc);
 		__rb_change_child(node, successor, tmp, root);
+
 		if (child2) {
 			successor->__rb_parent_color = pc;
 			rb_set_parent_color(child2, parent, RB_BLACK);
@@ -237,9 +261,21 @@ static __always_inline void
 rb_erase_augmented(struct rb_node *node, struct rb_root *root,
 		   const struct rb_augment_callbacks *augment)
 {
-	struct rb_node *rebalance = __rb_erase_augmented(node, root, augment);
+	struct rb_node *rebalance = __rb_erase_augmented(node, root,
+							 NULL, augment);
 	if (rebalance)
 		__rb_erase_color(rebalance, root, augment->rotate);
 }
 
-#endif	/* _TOOLS_LINUX_RBTREE_AUGMENTED_H */
+static __always_inline void
+rb_erase_augmented_cached(struct rb_node *node, struct rb_root_cached *root,
+			  const struct rb_augment_callbacks *augment)
+{
+	struct rb_node *rebalance = __rb_erase_augmented(node, &root->rb_root,
+							 &root->rb_leftmost,
+							 augment);
+	if (rebalance)
+		__rb_erase_color(rebalance, &root->rb_root, augment->rotate);
+}
+
+#endif /* _TOOLS_LINUX_RBTREE_AUGMENTED_H */