1 C cmpxchg-fail-unordered-2 1 C cmpxchg-fail-unordered-2
2 2
3 (* 3 (*
4 * Result: Sometimes 4 * Result: Sometimes
5 * 5 *
6 * Demonstrate that a failing cmpxchg() operat 6 * Demonstrate that a failing cmpxchg() operation does not act as either
7 * an acquire release operation. (In contrast 7 * an acquire release operation. (In contrast, a successful cmpxchg()
8 * does act as both an acquire and a release o 8 * does act as both an acquire and a release operation.)
9 *) 9 *)
10 10
11 {} 11 {}
12 12
13 P0(int *x, int *y) 13 P0(int *x, int *y)
14 { 14 {
15 int r1; 15 int r1;
16 16
17 WRITE_ONCE(*x, 1); 17 WRITE_ONCE(*x, 1);
18 r1 = cmpxchg(y, 0, 1); 18 r1 = cmpxchg(y, 0, 1);
19 } 19 }
20 20
21 P1(int *x, int *y) 21 P1(int *x, int *y)
22 { 22 {
23 int r1; 23 int r1;
24 int r2; 24 int r2;
25 25
26 r1 = cmpxchg(y, 0, 1); 26 r1 = cmpxchg(y, 0, 1);
27 r2 = READ_ONCE(*x); 27 r2 = READ_ONCE(*x);
28 } 28 }
29 29
30 exists (0:r1=0 /\ 1:r1=1 /\ 1:r2=0) 30 exists (0:r1=0 /\ 1:r1=1 /\ 1:r2=0)
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