Re: [patch] Real-Time Preemption, -RT-2.6.12-rc2-V0.7.44-00

Steven Rostedt
2005-04-05T19:40:14Z

Our first victim!! :-)

On Tue, 2005-04-05 at 20:06 +0100, Rui Nuno Capela wrote:
> >
> I'm having plenty of this on boot, on my SMP/HT desktop (P4/x86), while
> running RT-V0.7.44-01 (SMP+PREEMPT_RT):
>
> BUG: kstopmachine:xxxx RT task yield()-ing!
>
> See sample dmesg and .config on attach.
>
> OTOH, on my laptop (P4/UP), all seems to be clear fine.
>

The kstopmachine is only run on SMP environments, so it won't show up on
your UP machine.

> Is this something to be affraid of? :)
>

If your box is still running, then no. But it's now a chore to remove
the yield from this algorithm, since yields have a possibility to
deadlock the system. Although in this particular case, it may not be a
problem, since the threads that are being waited on are created for
other CPUs. But I haven't looked too much into what stop_machine is
doing so I can very well be wrong.

Thank you for reporting it, we want to weed out all the yields that a RT
task may call.

-- Steve