mirror of https://gitee.com/openkylin/linux.git
35 lines
694 B
Plaintext
35 lines
694 B
Plaintext
|
C LB+fencembonceonce+ctrlonceonce
|
||
|
|
|
||
|
|
(*
|
||
|
|
* Result: Never
|
||
|
|
*
|
||
|
|
* This litmus test demonstrates that lightweight ordering suffices for
|
||
|
|
* the load-buffering pattern, in other words, preventing all processes
|
||
|
|
* reading from the preceding process's write. In this example, the
|
||
|
|
* combination of a control dependency and a full memory barrier are enough
|
||
|
|
* to do the trick. (But the full memory barrier could be replaced with
|
||
|
|
* another control dependency and order would still be maintained.)
|
||
|
|
*)
|
||
|
|
|
||
|
|
{}
|
||
|
|
|
||
|
|
P0(int *x, int *y)
|
||
|
|
{
|
||
|
|
int r0;
|
||
|
|
|
||
|
|
r0 = READ_ONCE(*x);
|
||
|
|
if (r0)
|
||
|
|
WRITE_ONCE(*y, 1);
|
||
|
|
}
|
||
|
|
|
||
|
|
P1(int *x, int *y)
|
||
|
|
{
|
||
|
|
int r0;
|
||
|
|
|
||
|
|
r0 = READ_ONCE(*y);
|
||
|
|
smp_mb();
|
||
|
|
WRITE_ONCE(*x, 1);
|
||
|
|
}
|
||
|
|
|
||
|
|
exists (0:r0=1 /\ 1:r0=1)
|