rcutorture: Add reader-side tests of polling grace-period API

This commit adds reader-side testing of the polling grace-period API.
This testing verifies that a cookie obtained in an SRCU read-side critical
section does not get a true return from poll_state_synchronize_srcu()
within that same critical section.

Link: https://lore.kernel.org/rcu/20201112201547.GF3365678@moria.home.lan/
Reported-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 78ba95d..96d55f0 100644 (file)
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -1429,6 +1429,7 @@ rcutorture_loop_extend(int *readstate, struct torture_random_state *trsp,
  */
 static bool rcu_torture_one_read(struct torture_random_state *trsp)
 {
+       unsigned long cookie;
        int i;
        unsigned long started;
        unsigned long completed;
@@ -1444,6 +1445,8 @@ static bool rcu_torture_one_read(struct torture_random_state *trsp)
        WARN_ON_ONCE(!rcu_is_watching());
        newstate = rcutorture_extend_mask(readstate, trsp);
        rcutorture_one_extend(&readstate, newstate, trsp, rtrsp++);
+       if (cur_ops->get_gp_state && cur_ops->poll_gp_state)
+               cookie = cur_ops->get_gp_state();
        started = cur_ops->get_gp_seq();
        ts = rcu_trace_clock_local();
        p = rcu_dereference_check(rcu_torture_current,
@@ -1480,6 +1483,13 @@ static bool rcu_torture_one_read(struct torture_random_state *trsp)
        }
        __this_cpu_inc(rcu_torture_batch[completed]);
        preempt_enable();
+       if (cur_ops->get_gp_state && cur_ops->poll_gp_state)
+               WARN_ONCE(cur_ops->poll_gp_state(cookie),
+                         "%s: Cookie check 3 failed %s(%d) %lu->%lu\n",
+                         __func__,
+                         rcu_torture_writer_state_getname(),
+                         rcu_torture_writer_state,
+                         cookie, cur_ops->get_gp_state());
        rcutorture_one_extend(&readstate, 0, trsp, rtrsp);
        WARN_ON_ONCE(readstate & RCUTORTURE_RDR_MASK);
        // This next splat is expected behavior if leakpointer, especially