Commit 7e8b1e78 authored by Richard Braun's avatar Richard Braun Committed by Paul E. McKenney
Browse files

Documentation: Memory barrier semantics of atomic_xchg() 



Add atomic_xchg() to documentation for atomic operations and
memory barriers.

Signed-off-by: default avatarRichard Braun <rbraun@sceen.net>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: default avatarJosh Triplett <josh@joshtriplett.org>
parent 52494535

Documentation/atomic_ops.txt

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@@ -253,6 +253,8 @@ This performs an atomic exchange operation on the atomic variable v, setting 
the given new value.  It returns the old value that the atomic variable v had

the given new value.  It returns the old value that the atomic variable v had

just before the operation.

just before the operation.





atomic_xchg requires explicit memory barriers around the operation.



	int atomic_cmpxchg(atomic_t *v, int old, int new);

	int atomic_cmpxchg(atomic_t *v, int old, int new);





This performs an atomic compare exchange operation on the atomic value v,

This performs an atomic compare exchange operation on the atomic value v,

Documentation/memory-barriers.txt

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@@ -1685,6 +1685,7 @@ explicit lock operations, described later). These include: 




	xchg();

	xchg();

	cmpxchg();

	cmpxchg();

	atomic_xchg();

	atomic_cmpxchg();

	atomic_cmpxchg();

	atomic_inc_return();

	atomic_inc_return();

	atomic_dec_return();

	atomic_dec_return();