1 C cmpxchg-fail-unordered-1 1 C cmpxchg-fail-unordered-1
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 a
7 * full barrier. (In contrast, a successful c 7 * full barrier. (In contrast, a successful cmpxchg() does act as a
8 * full barrier.) 8 * full barrier.)
9 *) 9 *)
10 10
11 {} 11 {}
12 12
13 P0(int *x, int *y, int *z) 13 P0(int *x, int *y, int *z)
14 { 14 {
15 int r0; 15 int r0;
16 int r1; 16 int r1;
17 17
18 WRITE_ONCE(*x, 1); 18 WRITE_ONCE(*x, 1);
19 r1 = cmpxchg(z, 1, 0); 19 r1 = cmpxchg(z, 1, 0);
20 r0 = READ_ONCE(*y); 20 r0 = READ_ONCE(*y);
21 } 21 }
22 22
23 P1(int *x, int *y, int *z) 23 P1(int *x, int *y, int *z)
24 { 24 {
25 int r0; 25 int r0;
26 int r1; 26 int r1;
27 27
28 WRITE_ONCE(*y, 1); 28 WRITE_ONCE(*y, 1);
29 r1 = cmpxchg(z, 1, 0); 29 r1 = cmpxchg(z, 1, 0);
30 r0 = READ_ONCE(*x); 30 r0 = READ_ONCE(*x);
31 } 31 }
32 32
33 locations[0:r1;1:r1] 33 locations[0:r1;1:r1]
34 exists (0:r0=0 /\ 1:r0=0) 34 exists (0:r0=0 /\ 1:r0=0)
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