linux/tools/memory-model/litmus-tests/MP+onceassign+derefonce.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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C MP+onceassign+derefonce
(*
* Result: Never
*
* This litmus test demonstrates that rcu_assign_pointer() and
* rcu_dereference() suffice to ensure that an RCU reader will not see
* pre-initialization garbage when it traverses an RCU-protected data
* structure containing a newly inserted element.
*)
{
p=y;
}
P0(int *x, int **p) // Producer
{
WRITE_ONCE(*x, 1);
rcu_assign_pointer(*p, x);
}
P1(int *x, int **p) // Consumer
{
int *r0;
int r1;
rcu_read_lock();
r0 = rcu_dereference(*p);
r1 = READ_ONCE(*r0);
rcu_read_unlock();
}
exists (1:r0=x /\ 1:r1=0) (* Bad outcome. *)