Commit 396eba65 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Add quiescent states and boost states to show_rcu_gp_kthreads() output 



This commit adds each rcu_node structure's ->qsmask and "bBEG" output
indicating whether: (1) There is a boost kthread, (2) A reader needs
to be (or is in the process of being) boosted, (3) A reader is blocking
an expedited grace period, and (4) A reader is blocking a normal grace
period.  This helps diagnose RCU priority boosting failures.

Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent 30668200

kernel/rcu/tree.h

+1 −0
Original line number Diff line number Diff line
@@ -115,6 +115,7 @@ struct rcu_node { 
				/*  boosting for this rcu_node structure. */

	unsigned int boost_kthread_status;

				/* State of boost_kthread_task for tracing. */

	unsigned long n_boosts;	/* Number of boosts for this rcu_node structure. */

#ifdef CONFIG_RCU_NOCB_CPU

	struct swait_queue_head nocb_gp_wq[2];

				/* Place for rcu_nocb_kthread() to wait GP. */

kernel/rcu/tree_plugin.h

+1 −0
Original line number Diff line number Diff line
@@ -1098,6 +1098,7 @@ static int rcu_boost(struct rcu_node *rnp) 
	/* Lock only for side effect: boosts task t's priority. */

	rt_mutex_lock(&rnp->boost_mtx);

	rt_mutex_unlock(&rnp->boost_mtx);  /* Then keep lockdep happy. */

	rnp->n_boosts++;



	return READ_ONCE(rnp->exp_tasks) != NULL ||

	       READ_ONCE(rnp->boost_tasks) != NULL;

kernel/rcu/tree_stall.h

+9 −3
Original line number Diff line number Diff line
@@ -749,9 +749,15 @@ void show_rcu_gp_kthreads(void) 
		if (ULONG_CMP_GE(READ_ONCE(rcu_state.gp_seq),

				 READ_ONCE(rnp->gp_seq_needed)))

			continue;

		pr_info("\trcu_node %d:%d ->gp_seq %ld ->gp_seq_needed %ld\n",

			rnp->grplo, rnp->grphi, (long)data_race(rnp->gp_seq),

			(long)data_race(rnp->gp_seq_needed));

		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,

			(long)data_race(rnp->gp_seq), (long)data_race(rnp->gp_seq_needed),

			data_race(rnp->qsmask),

			".b"[!!data_race(rnp->boost_kthread_task)],

			".B"[!!data_race(rnp->boost_tasks)],

			".E"[!!data_race(rnp->exp_tasks)],

			".G"[!!data_race(rnp->gp_tasks)],

			data_race(rnp->n_boosts));

		if (!rcu_is_leaf_node(rnp))

			continue;

		for_each_leaf_node_possible_cpu(rnp, cpu) {