Re: [BUG 2.6.23-rc6-mm1] NMI Watchdog detected LOCKUP on CPU 0

Fengguang Wu
2007-09-23T05:53:18Z

On Sat, Sep 22, 2007 at 10:35:45PM -0700, Andrew Morton wrote:
> On Sun, 23 Sep 2007 13:30:40 +0800 Fengguang Wu <wfg@mail.ustc.edu.cn> wrote:
>
> > > That's interensting. serial_in(). We have had NMI watchdog expiries when
> > > the kernel is printing a large amount of stuff out a slow serial port with
> > > interrutps disabled. But I thought we'd pretty much plugged those problems
> > > by sprinkling touch_nmi_watchdog() in various places.
> > >
> > > Do you think this is what was happening on your system?
> >
> > Very likely. I'm running linux with cmdline
> > "root=/dev/sda1 ro nmi_watchdog=1 console=ttyS0,115200 console=tty0",
> > and doing a lot of printks at the time ;-)
>
> OK. We need to find a suitable place to poke yet another
> touch_nmi_watchdog(). Maybe we should give up and put one in
> printk().
>
> And you oopsed for different reasons in the nmi-watchdog handling
> code too. I think I'll pretend I didn't see that.

Let's forget it for now.
I can try Ingo's latency tracing patches at some convenient time.