Commit 72611ab9 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Add more diagnostics to expedited stall warning messages. 



This commit adds print statements that check the rcu_node structure to
find which ->expmask bits and which ->exp_tasks structures are blocking
the current expedited grace period.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 73f36f9d

kernel/rcu/tree.c

+21 −3
Original line number Diff line number Diff line
@@ -3745,6 +3745,7 @@ static void synchronize_sched_expedited_wait(struct rcu_state *rsp) 
	unsigned long jiffies_stall;

	unsigned long jiffies_start;

	unsigned long mask;

	int ndetected;

	struct rcu_node *rnp;

	struct rcu_node *rnp_root = rcu_get_root(rsp);

	int ret;
@@ -3767,14 +3768,16 @@ static void synchronize_sched_expedited_wait(struct rcu_state *rsp) 
		}

		pr_err("INFO: %s detected expedited stalls on CPUs/tasks: {",

		       rsp->name);

		ndetected = 0;

		rcu_for_each_leaf_node(rsp, rnp) {

			(void)rcu_print_task_exp_stall(rnp);

			ndetected = rcu_print_task_exp_stall(rnp);

			mask = 1;

			for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask <<= 1) {

				struct rcu_data *rdp;



				if (!(rnp->expmask & mask))

					continue;

				ndetected++;

				rdp = per_cpu_ptr(rsp->rda, cpu);

				pr_cont(" %d-%c%c%c", cpu,

					"O."[cpu_online(cpu)],
@@ -3783,8 +3786,23 @@ static void synchronize_sched_expedited_wait(struct rcu_state *rsp) 
			}

			mask <<= 1;

		}

		pr_cont(" } %lu jiffies s: %lu\n",

			jiffies - jiffies_start, rsp->expedited_sequence);

		pr_cont(" } %lu jiffies s: %lu root: %#lx/%c\n",

			jiffies - jiffies_start, rsp->expedited_sequence,

			rnp_root->expmask, ".T"[!!rnp_root->exp_tasks]);

		if (!ndetected) {

			pr_err("blocking rcu_node structures:");

			rcu_for_each_node_breadth_first(rsp, rnp) {

				if (rnp == rnp_root)

					continue; /* printed unconditionally */

				if (sync_rcu_preempt_exp_done(rnp))

					continue;

				pr_cont(" l=%u:%d-%d:%#lx/%c",

					rnp->level, rnp->grplo, rnp->grphi,

					rnp->expmask,

					".T"[!!rnp->exp_tasks]);

			}

			pr_cont("\n");

		}

		rcu_for_each_leaf_node(rsp, rnp) {

			mask = 1;

			for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask <<= 1) {