mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-09-15 23:25:07 +00:00
a591890c4e
This adds an example for the important RCU grace period guarantee, which shows an RCU reader can never span a grace period. Acked-by: Andrea Parri <parri.andrea@gmail.com> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
37 lines
704 B
Text
37 lines
704 B
Text
C RCU+sync+read
|
|
|
|
(*
|
|
* Result: Never
|
|
*
|
|
* This litmus test demonstrates that after a grace period, an RCU updater always
|
|
* sees all stores done in prior RCU read-side critical sections. Such
|
|
* read-side critical sections would have ended before the grace period ended.
|
|
*
|
|
* 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 = 0;
|
|
int y = 0;
|
|
}
|
|
|
|
P0(int *x, int *y)
|
|
{
|
|
rcu_read_lock();
|
|
WRITE_ONCE(*x, 1);
|
|
WRITE_ONCE(*y, 1);
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
P1(int *x, int *y)
|
|
{
|
|
int r0;
|
|
int r1;
|
|
|
|
r0 = READ_ONCE(*x);
|
|
synchronize_rcu();
|
|
r1 = READ_ONCE(*y);
|
|
}
|
|
|
|
exists (1:r0=1 /\ 1:r1=0)
|