linux-kernel - Re: NOHZ tick-stop error: Non-RCU local softirq work is pending

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Date:   Thu, 10 Dec 2020 15:56:37 +0100
From:   Frederic Weisbecker <frederic@...nel.org>
To:     "Paul E. McKenney" <paulmck@...nel.org>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: NOHZ tick-stop error: Non-RCU local softirq work is pending

Hi,

On Wed, Nov 18, 2020 at 09:52:18AM -0800, Paul E. McKenney wrote:
> Hello, Frederic,
> 
> Here is the last few months' pile of warnings from rcutorture runs.
> 
> 							Thanx, Paul
> 
> [  255.098527] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #282!!!
> [  414.534548] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #80!!!
> [ 3798.654736] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #80!!!
> [ 1718.589367] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #80!!!
> [ 6632.777655] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #80!!!
> [ 2873.688490] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #80!!!
> [ 3081.738937] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #80!!!
> [ 2673.597523] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #80!!!
> [ 1467.372887] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #80!!!
> [   34.371094] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #80!!!
> [ 1147.260097] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #80!!!
> [ 5066.699589] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #80!!!
> [  816.338843] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #80!!!
> [   34.338836] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #80!!!
> [ 1234.111394] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #280!!!
> [ 1282.109415] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #280!!!
> [  239.215890] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #280!!!
> [  367.918969] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #202!!!
> [ 1461.037894] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #80!!!
> [ 1503.810903] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #280!!!
> [ 1503.811939] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #280!!!
> [  699.514824] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #202!!!
> [  751.681629] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #280!!!
> [  287.770126] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #202!!!
> [  287.771096] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #202!!!
> [  648.009370] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #80!!!
> [  924.733405] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #202!!!
> [  924.734011] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #202!!!
> [ 1743.197353] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #02!!!
> [ 1528.161635] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #280!!!
> [ 1528.162313] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #280!!!
> [  265.201513] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #280!!!
> [  473.137587] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #202!!!
> [  187.375426] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #280!!!
> [ 1361.544451] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #80!!!
> [   79.519727] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #280!!!

Would you be willing to run TREE05 for me until it triggers the issue with:

      trace_event=softirq_raise trace_options=stacktrace

And with the below patch, thanks! (make sure you have CONFIG_EVENT_TRACING=y)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 81632cd5e3b7..1751e2d9a5b5 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -929,6 +929,8 @@ static bool can_stop_idle_tick(int cpu, struct tick_sched *ts)
 		    (local_softirq_pending() & SOFTIRQ_STOP_IDLE_MASK)) {
 			pr_warn("NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #%02x!!!\n",
 				(unsigned int) local_softirq_pending());
+			dump_stack();
+			ftrace_dump(DUMP_ORIG);
 			ratelimit++;
 		}
 		return false;