43 lines
892 B
Plaintext
43 lines
892 B
Plaintext
|
C RCU+sync+free
|
||
|
|
|
||
|
|
(*
|
||
|
|
* Result: Never
|
||
|
|
*
|
||
|
|
* This litmus test demonstrates that an RCU reader can never see a write that
|
||
|
|
* follows a grace period, if it did not see writes that precede that grace
|
||
|
|
* period.
|
||
|
|
*
|
||
|
|
* This is a typical pattern of RCU usage, where the write before the grace
|
||
|
|
* period assigns a pointer, and the writes following the grace period destroy
|
||
|
|
* the object that the pointer used to point to.
|
||
|
|
*
|
||
|
|
* This is one implication of the RCU grace-period guarantee, which says (among
|
||
|
|
* other things) that an RCU read-side critical section cannot span a grace period.
|
||
|
|
*)
|
||
|
|
|
||
|
|
{
|
||
|
|
int x = 1;
|
||
|
|
int *y = &x;
|
||
|
|
int z = 1;
|
||
|
|
}
|
||
|
|
|
||
|
|
P0(int *x, int *z, int **y)
|
||
|
|
{
|
||
|
|
int *r0;
|
||
|
|
int r1;
|
||
|
|
|
||
|
|
rcu_read_lock();
|
||
|
|
r0 = rcu_dereference(*y);
|
||
|
|
r1 = READ_ONCE(*r0);
|
||
|
|
rcu_read_unlock();
|
||
|
|
}
|
||
|
|
|
||
|
|
P1(int *x, int *z, int **y)
|
||
|
|
{
|
||
|
|
rcu_assign_pointer(*y, z);
|
||
|
|
synchronize_rcu();
|
||
|
|
WRITE_ONCE(*x, 0);
|
||
|
|
}
|
||
|
|
|
||
|
|
exists (0:r0=x /\ 0:r1=0)
|