# rcu_preempt in kernel 3.2.1-r2

## ivanoff

Hi there !

My gentoo machine, after switching to 3.2.1-gentoo-r2, does a lot of strange messages. On other occasions, my network card goes crazy, networking stops and ifconfig hangs eternally.

Switching back to 3.1.6 restores the normal situation without any problem to notice.

Here is an extract from /var/log/messages

```

Mar  4 09:38:07 ivanoff kernel: INFO: rcu_preempt detected stalls on CPUs/tasks: {} (detected by 2, t=60002 jiffies)

Mar  4 09:38:07 ivanoff kernel: INFO: Stall ended before state dump start

Mar  4 09:40:01 ivanoff cron[18312]: (root) CMD (test -x /usr/sbin/run-crons && /usr/sbin/run-crons)

Mar  4 09:41:07 ivanoff kernel: INFO: rcu_preempt detected stalls on CPUs/tasks: {} (detected by 2, t=240034 jiffies)

Mar  4 09:41:07 ivanoff kernel: INFO: Stall ended before state dump start

Mar  4 09:44:07 ivanoff kernel: INFO: rcu_preempt detected stalls on CPUs/tasks: {} (detected by 2, t=420066 jiffies)

Mar  4 09:44:07 ivanoff kernel: INFO: Stall ended before state dump start

Mar  4 09:47:07 ivanoff kernel: INFO: rcu_preempt detected stalls on CPUs/tasks: {} (detected by 2, t=600098 jiffies)

Mar  4 09:47:07 ivanoff kernel: INFO: Stall ended before state dump start

Mar  4 09:50:01 ivanoff cron[18474]: (root) CMD (test -x /usr/sbin/run-crons && /usr/sbin/run-crons)

Mar  4 09:50:07 ivanoff kernel: INFO: rcu_preempt detected stalls on CPUs/tasks: {} (detected by 2, t=780130 jiffies)

Mar  4 09:50:07 ivanoff kernel: INFO: Stall ended before state dump start

Mar  4 09:53:07 ivanoff kernel: INFO: rcu_preempt detected stalls on CPUs/tasks: {} (detected by 3, t=960162 jiffies)

Mar  4 09:53:07 ivanoff kernel: INFO: Stall ended before state dump start

Mar  4 09:56:07 ivanoff kernel: INFO: rcu_preempt detected stalls on CPUs/tasks: {} (detected by 2, t=1140194 jiffies)

Mar  4 09:56:07 ivanoff kernel: INFO: Stall ended before state dump start

Mar  4 09:59:01 ivanoff cron[18616]: (root) CMD (rm -f /var/spool/cron/lastrun/cron.hourly)

Mar  4 09:59:07 ivanoff kernel: INFO: rcu_preempt detected stalls on CPUs/tasks: {} (detected by 2, t=1320226 jiffies)

Mar  4 09:59:07 ivanoff kernel: INFO: Stall ended before state dump start

Mar  4 10:00:01 ivanoff cron[18620]: (root) CMD (test -x /usr/sbin/run-crons && /usr/sbin/run-crons)

Mar  4 10:02:07 ivanoff kernel: INFO: rcu_preempt detected stalls on CPUs/tasks: {} (detected by 1, t=1500258 jiffies)

Mar  4 10:02:07 ivanoff kernel: INFO: Stall ended before state dump start

Mar  4 10:05:07 ivanoff kernel: INFO: rcu_preempt detected stalls on CPUs/tasks: {} (detected by 2, t=1680290 jiffies)

Mar  4 10:05:07 ivanoff kernel: INFO: Stall ended before state dump start

Mar  4 10:08:07 ivanoff kernel: INFO: rcu_preempt detected stalls on CPUs/tasks: {} (detected by 2, t=1860322 jiffies)

Mar  4 10:08:07 ivanoff kernel: INFO: Stall ended before state dump start       

```

I can't even see who the culprit is... 

Any idea on how to get more info guys?

Thanks a lot

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## alinmesser

I think we may be having the same problem:

https://forums.gentoo.org/viewtopic-t-915106.html

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## ivanoff

It seems there is an ongoing issue with ipv6 lately : 

https://bugzilla.kernel.org/show_bug.cgi?id=42780

I'll try to deactivate it to see if it's related

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## ivanoff

I have tested 

alias net-pf-10 off             # IPv6

as advised in the kernel bug link and as for now, no more odd message.

Crossing my fingers.

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