[sched next] overflowed cpu time for kernel threads in /proc/PID/stat

From: Sergey Senozhatsky
Date: Tue Aug 20 2013 - 07:15:36 EST


Hello,
3.11.0-rc6-next-20130820

at some point an overflowed cpu time is reported in /proc/PID/stat

cat /proc/10/stat
10 (rcu_preempt) S 2 0 0 0 -1 2129984 0 0 0 0 0 406 0 0 20 0 1 0 10 0 0 18446744073709551615 0 0 0 0 0 0 0 2147483647 0 18446744073709551615 0 0 17 0 0 0 0 0 0 0 0 0 0 0 0 0 0
cat /proc/10/stat
10 (rcu_preempt) S 2 0 0 0 -1 2129984 0 0 0 0 0 406 0 0 20 0 1 0 10 0 0 18446744073709551615 0 0 0 0 0 0 0 2147483647 0 18446744073709551615 0 0 17 0 0 0 0 0 0 0 0 0 0 0 0 0 0
cat /proc/10/stat
10 (rcu_preempt) S 2 0 0 0 -1 2129984 0 0 0 0 0 407 0 0 20 0 1 0 10 0 0 18446744073709551615 0 0 0 0 0 0 0 2147483647 0 18446744073709551615 0 0 17 0 0 0 0 0 0 0 0 0 0 0 0 0 0
cat /proc/10/stat
10 (rcu_preempt) S 2 0 0 0 -1 2129984 0 0 0 0 0 407 0 0 20 0 1 0 10 0 0 18446744073709551615 0 0 0 0 0 0 0 2147483647 0 18446744073709551615 0 0 17 0 0 0 0 0 0 0 0 0 0 0 0 0 0
cat /proc/10/stat
10 (rcu_preempt) S 2 0 0 0 -1 2129984 0 0 0 0 1844674407370 477 0 0 20 0 1 0 10 0 0 18446744073709551615 0 0 0 0 0 0 0 2147483647 0 18446744073709551615 0 0 17 0 0 0 0 0 0 0 0 0 0 0 0 0 0
^^^^^^^^^
cat /proc/10/stat
10 (rcu_preempt) S 2 0 0 0 -1 2129984 0 0 0 0 1844674407370 597 0 0 20 0 1 0 10 0 0 18446744073709551615 0 0 0 0 0 0 0 2147483647 0 18446744073709551615 0 0 17 0 0 0 0 0 0 0 0 0 0 0 0 0 0

(seems there are several more -1UL in output)


oddly enough, I see this happening only for RCU

ps aux | grep rcu
root 8 0.0 0.0 0 0 ? S 12:42 0:00 [rcuc/0]
root 9 0.0 0.0 0 0 ? S 12:42 0:00 [rcub/0]
root 10 62422329 0.0 0 0 ? R 12:42 21114581:37 [rcu_preempt]
root 11 0.1 0.0 0 0 ? S 12:42 0:02 [rcuop/0]
root 12 62422329 0.0 0 0 ? S 12:42 21114581:35 [rcuop/1]

-ss
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