blob: 4ee67e12f513a59963bd318582cf5cb880ebdacc [file] [log] [blame]
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;
r0 = rcu_dereference(*y);
r1 = READ_ONCE(*r0);
P1(int *x, int *z, int **y)
rcu_assign_pointer(*y, z);
WRITE_ONCE(*x, 0);
exists (0:r0=x /\ 0:r1=0)