blob: f8ca1229857ad5cabb24b0f31760f17acfc73a39 (
plain) (
blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
|
C MP+fencewmbonceonce+fencermbonceonce
(*
* Result: Never
*
* This litmus test demonstrates that smp_wmb() and smp_rmb() provide
* sufficient ordering for the message-passing pattern. However, it
* is usually better to use smp_store_release() and smp_load_acquire().
*)
{}
P0(int *buf, int *flag) // Producer
{
WRITE_ONCE(*buf, 1);
smp_wmb();
WRITE_ONCE(*flag, 1);
}
P1(int *buf, int *flag) // Consumer
{
int r0;
int r1;
r0 = READ_ONCE(*flag);
smp_rmb();
r1 = READ_ONCE(*buf);
}
exists (1:r0=1 /\ 1:r1=0) (* Bad outcome. *)
|
