Re: 4BSD Scheduler Problem on 5.3

From: Robert Watson (rwatson_at_FreeBSD.org)
Date: 04/01/05

  • Next message: John-Mark Gurney: "Re: So, who makes this one run FreeBSD? ;-)" 
    Date: Fri, 1 Apr 2005 01:03:14 +0000 (GMT)
To: John Baldwin <jhb@FreeBSD.org>

    On Thu, 31 Mar 2005, John Baldwin wrote:

    > On Thursday 31 March 2005 03:38 pm, William Michael Grim wrote:
    > > Hello.
    > >
    > > I keep having kernel panics every couple weeks on my system. It occurs in
    > > the sched_switch() function. There are several other statements in the
    > > backtrace involving "??"; what are those?
    > >
    > > I have attached the dump output and system info to this email. Any
    > > feedback would be helpful.
    > >
    > > Thanks so much for your help.
    >
    > The real trace ends with Xint0x80_syscall(). The rest after that is
    > garbage memory. Your real problem is in exit1() or ttywakeup(). Since
    > ttywakeup() doesn't call exit1() (AFAIK), the exit1() frame is probably
    > bogus (gdb doesn't grok trapframes maybe?) and the real bug is a NULL
    > pointer deref in ttywakeup(). Perhaps it's a bug in the ptc driver?
    > (ptcopen is in the trace). What is the ptc driver anyway?

    I think we have a race in -STABLE relating to tty wakeups and
    open/close/device teardown. I've seen a panic relating to sio during a
    tty close on RELENG_5 about 5-6 months ago, but was unable to get a dump.
    Scott has since fixed dumps with twe, but I've not yet been able to get
    the bug to recur. I'll give it another try.

    Robert N M Watson

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