rcu: Make rcutorture fakewriters invoke rcu_barrier()

The current rcutorture rcu_barrier() testing never intentionally runs
more than one instance of rcu_barrier() at a given time.  This fails
to test the the shiny new concurrency features of rcu_barrier().  This
commit therefore modifies the rcutorture fakewriter kthread to randomly
invoke rcu_barrier() rather than the usual synchronize_rcu().

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c
index 045a3dc233ea..c279ee920947 100644
--- a/kernel/rcutorture.c
+++ b/kernel/rcutorture.c
@@ -1025,7 +1025,11 @@ rcu_torture_fakewriter(void *arg)
         do {
                 schedule_timeout_uninterruptible(1 + rcu_random(&rand)%10);
                 udelay(rcu_random(&rand) & 0x3ff);
-                cur_ops->sync();
+                if (cur_ops->cb_barrier != NULL &&
+                    rcu_random(&rand) % (nfakewriters * 8) == 0)
+                        cur_ops->cb_barrier();
+                else
+                        cur_ops->sync();
                 rcu_stutter_wait("rcu_torture_fakewriter");
         } while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP);