mirror of https://github.com/Qortal/Brooklyn
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
42 lines
892 B
42 lines
892 B
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)
|
|
|