From 4a6dae6d382e9edf3ff440b819e554ed706359bc Mon Sep 17 00:00:00 2001 From: Nick Piggin Date: Sun, 13 Nov 2005 16:07:24 -0800 Subject: [PATCH] atomic: cmpxchg Introduce an atomic_cmpxchg operation. Signed-off-by: Nick Piggin Cc: "Paul E. McKenney" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/atomic_ops.txt | 15 +++++++++++++++ 1 file changed, 15 insertions(+) (limited to 'Documentation') diff --git a/Documentation/atomic_ops.txt b/Documentation/atomic_ops.txt index 8eedaa24f5e2..f1744161ef06 100644 --- a/Documentation/atomic_ops.txt +++ b/Documentation/atomic_ops.txt @@ -115,6 +115,21 @@ boolean is return which indicates whether the resulting counter value is negative. It requires explicit memory barrier semantics around the operation. +Finally: + + int atomic_cmpxchg(atomic_t *v, int old, int new); + +This performs an atomic compare exchange operation on the atomic value v, +with the given old and new values. Like all atomic_xxx operations, +atomic_cmpxchg will only satisfy its atomicity semantics as long as all +other accesses of *v are performed through atomic_xxx operations. + +atomic_cmpxchg requires explicit memory barriers around the operation. + +The semantics for atomic_cmpxchg are the same as those defined for 'cas' +below. + + If a caller requires memory barrier semantics around an atomic_t operation which does not return a value, a set of interfaces are defined which accomplish this: -- cgit v1.2.3-59-g8ed1b