Re: Resent: BUG in RT 45-01 when RT program dumps core

[Steven Rostedt <rostedt@goodmis.org>]

On Thu, 2005-05-19 at 08:36 +0200, kus Kusche Klaus wrote:
> Quoting my mail from Apr 11th (received no response up to now):

Sorry, I must have missed it, I try to keep up on all mail associated to
Ingo's RT kernel. Including Ingo on the list is the right thing to do.

> > When a process running with RT priority dumps core,
> > I get the following BUG:
> > 
> > Apr 11 13:44:23 OF455 kern.err kernel: BUG: rtc2:833 RT task 
> > yield()-ing!

This is a check that we have to flag when a RT task calls yield.  This
in itself may not really be a bug, but it can be. There's places in the
kernel that call yield to wait for a bit to clear or a lock to become
unlock (doesn't grab it directly to prevent deadlocking).  This may be
OK with non RT tasks, since other tasks will get a chance to run. But
with RT tasks, a yield won't yield to any task with less priority than
the RT task. So if the RT task is yielding to let a lower priority task
do something it needs, it will in effect deadlock the system for all
tasks lower in priority than itself.

> This is still absolutely reproducable, in RT 7.47-01,
> with slight variations in the stack trace.
> 
> Is this something to worry about?

I'll take a look into it.


Ingo,

Did you get my patch to fix the kstop_machine yielding problem?

-- Steve