linux-kernel - [PATCH rcu 13/32] rcu-tasks: Add slow-IPI indicator to RCU Tasks Trace stall warnings

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Date:   Mon, 20 Jun 2022 15:53:52 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     rcu@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, kernel-team@...com,
        rostedt@...dmis.org, "Paul E. McKenney" <paulmck@...nel.org>,
        Neeraj Upadhyay <quic_neeraju@...cinc.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        KP Singh <kpsingh@...nel.org>
Subject: [PATCH rcu 13/32] 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@...nel.org>
Cc: Neeraj Upadhyay <quic_neeraju@...cinc.com>
Cc: Eric Dumazet <edumazet@...gle.com>
Cc: Alexei Starovoitov <ast@...nel.org>
Cc: Andrii Nakryiko <andrii@...nel.org>
Cc: Martin KaFai Lau <kafai@...com>
Cc: KP Singh <kpsingh@...nel.org>
---
 kernel/rcu/tasks.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 6b44c69eeca88..1cfbebf2b5977 100644
--- 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",
-- 
2.31.1.189.g2e36527f23