NOHZ: local_softirq_pending

[Iratxo Pichel Ortiz <ipichel@albentia.com>]

Hi there,

I hope that someone in this list could help me trace down this issue I 
am seeing.

I am using 2.6.30-rt16 RT Kernel on a IXP425 system. The system is 
running an experimental comm stack that has been working quite well with 
2.6.26-rt2 for a very long time (> 100days).

When the system boots, every 180s aprox, I see this traces in the dmesg:
42949422.930000] NOHZ: local_softirq_pending 02
[42949422.940000] NOHZ: local_softirq_pending 02
[42949422.950000] NOHZ: local_softirq_pending 02
[42949422.960000] ISR HIHG LATENCY 30073
[42949596.920000] NOHZ: local_softirq_pending 02
[42949596.930000] NOHZ: local_softirq_pending 02
[42949596.940000] NOHZ: local_softirq_pending 02
[42949596.950000] NOHZ: local_softirq_pending 02
[42949596.960000] ISR HIHG LATENCY 40066

The "ISR HIGH LATENCY" is small latency measurement that I have done in 
the ISR function of the driver. Hw is ticking the system every 2.5ms and 
the usual run-time of the ISR handler is well under 200us. Every aprox 
180seconds, suddenly this run-time get as high as 50ms.

It is very highly probable that the problem is inside my driver, because 
if I dont load the modules, this "NOHZ..." trace is not shown. Anyway, I 
would like to know if this "issue" is triggered by some known cause, or 
at least any idea where to start looking at.

Please, CC me as I am not subscribed to the list.

Thank you very much in advance and best regards!

    Iratxo.


Another run:
[   96.950000] NOHZ: local_softirq_pending 02
[   96.960000] NOHZ: local_softirq_pending 02
[   96.970000] NOHZ: local_softirq_pending 02
[   97.000000] ISR HIGH LATENCY 50068
[  270.000000] ISR HIGH LATENCY 50048
[  463.000000] ISR HIGH LATENCY 50049
[  643.000000] ISR HIGH LATENCY 50047

-- 
Iratxo Pichel Ortiz
Software Development Manager

Albentia Systems S.A.
http://www.albentia.com

Tel: +34 914400567
Cel: +34 663808405
Fax: +34 914400569

C\Margarita Salas 22
Parque Tecnológico de Leganés
Leganés (28918)
Madrid
Spain

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