From 02c608c1fefe821a4c6fc34c45a0dea3cebf4764 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Sun, 24 Feb 2008 00:03:29 +0300 Subject: documentation: atomic_add_unless() doesn't imply mb() on failure (sorry for being offtpoic, but while experts are here...) A "typical" implementation of atomic_add_unless() can return 0 immediately after the first atomic_read() (before doing cmpxchg). In that case it doesn't provide any barrier semantics. See include/asm-ia64/atomic.h as an example. We should either change the implementation, or fix the docs. Signed-off-by: Oleg Nesterov Acked-by: Nick Piggin Signed-off-by: Linus Torvalds --- Documentation/memory-barriers.txt | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'Documentation/memory-barriers.txt') diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt index 4e17beba2379..1f506f7830ec 100644 --- a/Documentation/memory-barriers.txt +++ b/Documentation/memory-barriers.txt @@ -1493,7 +1493,7 @@ explicit lock operations, described later). These include: atomic_dec_and_test(); atomic_sub_and_test(); atomic_add_negative(); - atomic_add_unless(); + atomic_add_unless(); /* when succeeds (returns 1) */ test_and_set_bit(); test_and_clear_bit(); test_and_change_bit(); -- cgit v1.2.3