rcu: More clearly identify grace-period kthread stack dump

It is not always obvious that the stack dump from a starved grace-period
kthread isn't instead that of a CPU stalling the current grace period.
This commit therefore adds a pr_err() flagging these dumps.

Reported-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 86fc087c7777ea648b913d265607d8dd9957dd04..4d7c727020f0f84d01f601994f272d235d78daf6 100644 (file)
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1350,6 +1350,7 @@ static void rcu_check_gp_kthread_starvation(struct rcu_state *rsp)
                       rsp->gp_kthread ? rsp->gp_kthread->state : ~0,
                       rsp->gp_kthread ? task_cpu(rsp->gp_kthread) : -1);
                if (rsp->gp_kthread) {
+                       pr_err("RCU grace-period kthread stack dump:\n");
                        sched_show_task(rsp->gp_kthread);
                        wake_up_process(rsp->gp_kthread);
                }