rcu-tasks: Add slow-IPI indicator to RCU Tasks Trace stall warnings

This commit adds a "I" indicator to the RCU Tasks Trace CPU stall
warning when an IPI directed to a task has thus far failed to arrive.
This serves as a debugging aid.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: KP Singh <kpsingh@kernel.org>

diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 6b44c69..1cfbebf 100644 (file)
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -1497,8 +1497,9 @@ static void show_stalled_task_trace(struct task_struct *t, bool *firstreport)
        }
        cpu = task_cpu(t);
        if (!task_call_func(t, trc_check_slow_task, &trc_rdr))
-               pr_alert("P%d: %c\n",
+               pr_alert("P%d: %c%c\n",
                         t->pid,
+                        ".I"[t->trc_ipi_to_cpu >= 0],
                         ".i"[is_idle_tsk]);
        else
                pr_alert("P%d: %c%c%c nesting: %d%c cpu: %d\n",