Commit 725969ac authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Do not NMI offline CPUs 



Currently, RCU CPU stall warning messages will NMI whatever CPU looks
like it is blocking either the current grace period or the grace-period
kthread.  This can produce confusing output if the target CPU is offline.
This commit therefore checks for offline CPUs.

Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent 243027a3

kernel/rcu/tree_stall.h

+12 −5
Original line number Diff line number Diff line
@@ -333,9 +333,12 @@ static void rcu_dump_cpu_stacks(void) 
	rcu_for_each_leaf_node(rnp) {

		raw_spin_lock_irqsave_rcu_node(rnp, flags);

		for_each_leaf_node_possible_cpu(rnp, cpu)

			if (rnp->qsmask & leaf_node_cpu_bit(rnp, cpu))

				if (!trigger_single_cpu_backtrace(cpu))

			if (rnp->qsmask & leaf_node_cpu_bit(rnp, cpu)) {

				if (cpu_is_offline(cpu))

					pr_err("Offline CPU %d blocking current GP.\n", cpu);

				else if (!trigger_single_cpu_backtrace(cpu))

					dump_cpu_task(cpu);

			}

		raw_spin_unlock_irqrestore_rcu_node(rnp, flags);

	}

}
@@ -466,10 +469,14 @@ static void rcu_check_gp_kthread_starvation(void) 
			pr_err("RCU grace-period kthread stack dump:\n");

			sched_show_task(gpk);

			if (cpu >= 0) {

				pr_err("Stack dump where RCU grace-period kthread last ran:\n");

				if (cpu_is_offline(cpu)) {

					pr_err("RCU GP kthread last ran on offline CPU %d.\n", cpu);

				} else  {

					pr_err("Stack dump where RCU GP kthread last ran:\n");

					if (!trigger_single_cpu_backtrace(cpu))

						dump_cpu_task(cpu);

				}

			}

			wake_up_process(gpk);

		}

	}