rcu: Make show_rcu_gp_kthreads() dump rcu_node structures blocking GP

Currently, show_rcu_gp_kthreads() only dumps rcu_node structures that
have outdated ideas of the current grace-period number.  This commit
also dumps those that are in any way blocking the current grace period.
This helps diagnose RCU priority boosting failures.

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

diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index c1f8386..e6bd518 100644 (file)
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -746,8 +746,9 @@ void show_rcu_gp_kthreads(void)
                data_race(rcu_state.gp_max),
                data_race(rcu_state.gp_flags));
        rcu_for_each_node_breadth_first(rnp) {
-               if (ULONG_CMP_GE(READ_ONCE(rcu_state.gp_seq),
-                                READ_ONCE(rnp->gp_seq_needed)))
+               if (ULONG_CMP_GE(READ_ONCE(rcu_state.gp_seq), READ_ONCE(rnp->gp_seq_needed)) &&
+                   !data_race(rnp->qsmask) && !data_race(rnp->boost_tasks) &&
+                   !data_race(rnp->exp_tasks) && !data_race(rnp->gp_tasks))
                        continue;
                pr_info("\trcu_node %d:%d ->gp_seq %ld ->gp_seq_needed %ld ->qsmask %#lx %c%c%c%c ->n_boosts %ld\n",
                        rnp->grplo, rnp->grphi,