standard ps output identifies kernel threads by putting them in
square brackets, as in:

UID        PID  PPID  C STIME TTY          TIME CMD
root         1     0  0 Jun21 ?        00:00:01 /sbin/init
root         2     0  0 Jun21 ?        00:00:00 [kthreadd]
root         3     2  0 Jun21 ?        00:00:39 [ksoftirqd/0]
root         5     2  0 Jun21 ?        00:00:00 [kworker/0:0H]
root         7     2  0 Jun21 ?        00:00:10 [migration/0]
root         8     2  0 Jun21 ?        00:00:00 [rcu_bh]
root         9     2  0 Jun21 ?        00:06:52 [rcu_sched]
... snip ...

but what *exactly* does the ps command test to see if a task is a
kernel thread? i'm poking through the code for ps right now and it's
not obvious.

  it so happens that the parent [kthreadd] always has PID 2, and all
subsequent kernel threads have a PPID of 2, so maybe it's that simple.
or is it checking some field in the task struct? anyone?

rday

-- 

========================================================================
Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
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