linux-stable/tools/memory-model/litmus-tests/MP+fencewmbonceonce+fencermbonceonce.litmus
Akira Yokosawa 5c587f9b9c tools/memory-model: Remove redundant initialization in litmus tests
This is a revert of commit 1947bfcf81 ("tools/memory-model: Add types
to litmus tests") with conflict resolutions.

klitmus7 [1] is aware of default types of "int" and "int*".
It accepts litmus tests for herd7 without extra type info unless
non-"int" variables are referenced by an "exists", "locations",
or "filter" directive.

[1]: Tested with klitmus7 versions 7.49 or later.

Suggested-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-01-04 14:40:49 -08:00

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Text

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. *)