rcu-tasks: Check for abandoned callbacks

This commit adds a debugging scan for callbacks that got lost during a
callback-queueing transition.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 3925e32..b8690a4 100644 (file)
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -439,6 +439,11 @@ static int rcu_tasks_need_gpcb(struct rcu_tasks *rtp)
                        WRITE_ONCE(rtp->percpu_dequeue_lim, 1);
                        pr_info("Completing switch %s to CPU-0 callback queuing.\n", rtp->name);
                }
+               for (cpu = rtp->percpu_dequeue_lim; cpu < nr_cpu_ids; cpu++) {
+                       struct rcu_tasks_percpu *rtpcp = per_cpu_ptr(rtp->rtpcpu, cpu);
+
+                       WARN_ON_ONCE(rcu_segcblist_n_cbs(&rtpcp->cblist));
+               }
                raw_spin_unlock_irqrestore(&rtp->cbs_gbl_lock, flags);
        }