Commit d6ad6063 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu-tasks: Ensure RCU Tasks Trace loops have quiescent states 

The RCU Tasks Trace grace-period kthread loops across all CPUs, and
there can be quite a few CPUs, with some commercially available systems
sporting well over a thousand of them.  Some of these loops can feature
IPIs, which can take some time.  This commit therefore places a call to
cond_resched_tasks_rcu_qs() in each such loop.

Link: https://docs.google.com/document/d/1V0YnG1HTWMt9WHJjroiJL9lf-hMrud4v8Fn3fhyY0cI/edit?usp=sharing


Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent fcd53c8a

kernel/rcu/tasks.h

+3 −0
Original line number Diff line number Diff line
@@ -1500,6 +1500,7 @@ static void rcu_tasks_trace_pregp_step(struct list_head *hop) 
		if (rcu_tasks_trace_pertask_prep(t, true))

			trc_add_holdout(t, hop);

		rcu_read_unlock();

		cond_resched_tasks_rcu_qs();

	}



	// Only after all running tasks have been accounted for is it
@@ -1520,6 +1521,7 @@ static void rcu_tasks_trace_pregp_step(struct list_head *hop) 
			raw_spin_lock_irqsave_rcu_node(rtpcp, flags);

		}

		raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags);

		cond_resched_tasks_rcu_qs();

	}



	// Re-enable CPU hotplug now that the holdout list is populated.
@@ -1619,6 +1621,7 @@ static void check_all_holdout_tasks_trace(struct list_head *hop, 
			trc_del_holdout(t);

		else if (needreport)

			show_stalled_task_trace(t, firstreport);

		cond_resched_tasks_rcu_qs();

	}



	// Re-enable CPU hotplug now that the holdout list scan has completed.