Messages in this thread Patch in this message | | | From | Davidlohr Bueso <> | Subject | [PATCH] rbtree: use READ_ONCE in RB_EMPTY_ROOT | Date | Mon, 11 Jan 2016 10:22:43 -0800 |
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With d72da4a4d97 (rbtree: Make lockless searches non-fatal) our rbtrees provide weak guarantees that allows us to do lockless (and very speculative) reads of the tree. Such readers cannot see partial stores on nodes, ie left/right as well as root. As such, similar to the WRITE_ONCE semantics when doing rotations, use READ_ONCE when checking the root node in RB_EMPTY_ROOT.
Signed-off-by: Davidlohr Bueso <dbueso@suse.de> --- include/linux/rbtree.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/rbtree.h b/include/linux/rbtree.h index a5aa7ae..b690009 100644 --- a/include/linux/rbtree.h +++ b/include/linux/rbtree.h @@ -50,7 +50,7 @@ struct rb_root { #define RB_ROOT (struct rb_root) { 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) \ -- 2.1.4
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