rcutorture: Dump GP kthread state on insufficient cb-flood laundering

If a callback flood prevents grace period from completing, rcutorture
does a WARN_ON().  Avoiding this WARN_ON() currently requires that at
least three grace periods elapse during an eight-second callback-flood
interval.  Unfortunately, the current debug information does not include
anything about the grace-period state.  This commit therefore adds a
call to cur_ops->gp_kthread_dbg(), if this function pointer is non-NULL.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 6611ef3e71c33fd68eb7acc8e3d1767afd7e3dc7..eff51a26216f300f51bb1164634bfe262ed63475 100644 (file)
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -2832,7 +2832,8 @@ static void rcu_torture_fwd_prog_cr(struct rcu_fwd *rfp)
 
        if (!torture_must_stop() && !READ_ONCE(rcu_fwd_emergency_stop) &&
            !shutdown_time_arrived()) {
-               WARN_ON(n_max_gps < MIN_FWD_CBS_LAUNDERED);
+               if (WARN_ON(n_max_gps < MIN_FWD_CBS_LAUNDERED) && cur_ops->gp_kthread_dbg)
+                       cur_ops->gp_kthread_dbg();
                pr_alert("%s Duration %lu barrier: %lu pending %ld n_launders: %ld n_launders_sa: %ld n_max_gps: %ld n_max_cbs: %ld cver %ld gps %ld #online %u\n",
                         __func__,
                         stoppedat - rfp->rcu_fwd_startat, jiffies - stoppedat,