On 25.03.20 08:59, Bradley Valdenebro Peter (DC-AE/ESW52) wrote:

Thanks for your support Jan.

We have already tried with ftrace and we couldn't reproduce the issue. We think 
because the introduced overhead. We usually record the following events:

        sudo trace-cmd start -e ipi -e irq -e rcu -e workqueue_execute_end -e 
workqueue_execute_start -e mm_page_alloc -e mm_page_free
                        -e sched_migrate_task -e sched_switch -e 
cobalt_irq_exit -e cobalt_irq_entry -e cobalt_thread_migrate -e 
                        -e cobalt_head_sysexit -e cobalt_clock_entry -e 

Would changing to trace-cmd record -e "cobalt*" -e sched -e signal make a 

If you already have troubles reproducing with your reduced event set, this won't be easier with the extended cobalt events. I would rather try to reduce the set further, maybe leaving out rcu, syscalls, allocations and maybe even interrupts.

We have also tried using the ipipe tracer but there we also had no luck. We 
didn't use xntrace_user_freeze() but we monitored the trace IRQs-off times in 
Using xntrace_user_freeze() might be worth a try.

If you can reproduce under enabled ipipe trace, then this makes sense.


Best regards,

Peter Bradley
-----Original Message-----
From: Jan Kiszka <jan.kis...@siemens.com>
Sent: 24 March 2020 12:53
To: Bradley Valdenebro Peter (DC-AE/ESW52) 
<peter.bradleyvaldene...@boschrexroth.nl>; xenomai@xenomai.org
Subject: Re: RT thread seems blocked

On 24.03.20 12:43, Bradley Valdenebro Peter (DC-AE/ESW52) wrote:

We run some tests during the weekend and although we have less occurrences we 
still indeed see them.

One interesting thing we see besides the 1ms stalling is that sometimes we see 
over 100us between IRQ and ISR start.
At this point we do not know how to proceed further. Any help or suggestion is 
greatly appreciated.

That is usually where you should start to look into tracing. Option A is 
event-level tracing via standard ftrace. Use

trace-cmd record -e "cobalt*" -e sched -e signal

to record such a trace. Ideally instrument the point where the latency is off in your 
application via xnftrace_printf() (will leave a mark in that recorded trace). Check via 
"trace-cmd report" if the schedule around that peak is what you would expect.

For digging even deeper, down to function level:
specifically look into xntrace_user_freeze(), calling that from your 
application when you spot an excessive latency to stop the trace.

If the result is not clear to you, share it to get a community inspection.


Siemens AG, Corporate Technology, CT RDA IOT SES-DE Corporate Competence Center 
Embedded Linux

Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux

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