linux/Documentation/litmus-tests/atomic/cmpxchg-fail-unordered-1.litmus
Paul E. McKenney 2ba5b4130e Documentation/litmus-tests: Make cmpxchg() tests safe for klitmus
The four litmus tests in Documentation/litmus-tests/atomic do not
declare all of their local variables.  Although this is just fine for LKMM
analysis by herd7, it causes build failures when run in-kernel by klitmus.
This commit therefore adjusts these tests to declare all local variables.

Reported-by: Andrea Parri <parri.andrea@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Andrea Parri <parri.andrea@gmail.com>
2024-05-06 14:29:21 -07:00

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Plaintext

C cmpxchg-fail-unordered-1
(*
* Result: Sometimes
*
* Demonstrate that a failing cmpxchg() operation does not act as a
* full barrier. (In contrast, a successful cmpxchg() does act as a
* full barrier.)
*)
{}
P0(int *x, int *y, int *z)
{
int r0;
int r1;
WRITE_ONCE(*x, 1);
r1 = cmpxchg(z, 1, 0);
r0 = READ_ONCE(*y);
}
P1(int *x, int *y, int *z)
{
int r0;
int r1;
WRITE_ONCE(*y, 1);
r1 = cmpxchg(z, 1, 0);
r0 = READ_ONCE(*x);
}
locations[0:r1;1:r1]
exists (0:r0=0 /\ 1:r0=0)