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

From: Steven Rostedt (rostedt_at_goodmis.org)
Date: 05/19/05

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    To: kus Kusche Klaus <kus@keba.com>
Date:	Thu, 19 May 2005 07:56:03 -0400

    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

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