1 C cmpxchg-fail-ordered-2 1 C cmpxchg-fail-ordered-2
2 2
3 (* 3 (*
4 * Result: Never 4 * Result: Never
5 * 5 *
6 * Demonstrate use of smp_mb__after_atomic() t 6 * Demonstrate use of smp_mb__after_atomic() to make a failing cmpxchg
7 * operation have acquire ordering. 7 * operation have acquire ordering.
8 *) 8 *)
9 9
10 {} 10 {}
11 11
12 P0(int *x, int *y) 12 P0(int *x, int *y)
13 { 13 {
14 int r1; 14 int r1;
15 15
16 WRITE_ONCE(*x, 1); 16 WRITE_ONCE(*x, 1);
17 r1 = cmpxchg(y, 0, 1); 17 r1 = cmpxchg(y, 0, 1);
18 } 18 }
19 19
20 P1(int *x, int *y) 20 P1(int *x, int *y)
21 { 21 {
22 int r1; 22 int r1;
23 int r2; 23 int r2;
24 24
25 r1 = cmpxchg(y, 0, 1); 25 r1 = cmpxchg(y, 0, 1);
26 smp_mb__after_atomic(); 26 smp_mb__after_atomic();
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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