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authorNick Piggin <nickpiggin@yahoo.com.au>2005-11-13 19:07:24 -0500
committerLinus Torvalds <torvalds@g5.osdl.org>2005-11-13 21:14:16 -0500
commit4a6dae6d382e9edf3ff440b819e554ed706359bc (patch)
tree2945a5095973e2ecf05b503d6deb859083045b8e /Documentation
parent53e86b91b7ae66d4c2757195cbd42e00d9199cf2 (diff)
[PATCH] atomic: cmpxchg
Introduce an atomic_cmpxchg operation. Signed-off-by: Nick Piggin <npiggin@suse.de> Cc: "Paul E. McKenney" <paulmck@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/atomic_ops.txt15
1 files changed, 15 insertions, 0 deletions
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
115is negative. It requires explicit memory barrier semantics around the 115is negative. It requires explicit memory barrier semantics around the
116operation. 116operation.
117 117
118Finally:
119
120 int atomic_cmpxchg(atomic_t *v, int old, int new);
121
122This performs an atomic compare exchange operation on the atomic value v,
123with the given old and new values. Like all atomic_xxx operations,
124atomic_cmpxchg will only satisfy its atomicity semantics as long as all
125other accesses of *v are performed through atomic_xxx operations.
126
127atomic_cmpxchg requires explicit memory barriers around the operation.
128
129The semantics for atomic_cmpxchg are the same as those defined for 'cas'
130below.
131
132
118If a caller requires memory barrier semantics around an atomic_t 133If a caller requires memory barrier semantics around an atomic_t
119operation which does not return a value, a set of interfaces are 134operation which does not return a value, a set of interfaces are
120defined which accomplish this: 135defined which accomplish this: