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| author | Davidlohr Bueso <dave@stgolabs.net> | 2016-01-20 15:00:42 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-01-20 17:09:18 -0800 |
| commit | a460bece027301e079b9e53c5e0f67c8e3eaebc1 (patch) | |
| tree | c53d99607bbbb604bb48cc44d889459d354acd7f | |
| parent | a253f1eee6c471d5418983ca9aa9c756e7db5db9 (diff) | |
| download | linux-a460bece027301e079b9e53c5e0f67c8e3eaebc1.tar.bz2 | |
rbtree: use READ_ONCE in RB_EMPTY_ROOT
With commit 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>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Michel Lespinasse <walken@google.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | include/linux/rbtree.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/include/linux/rbtree.h b/include/linux/rbtree.h index a5aa7ae671f4..b6900099ea81 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) \ |