lkml.org 
[lkml]   [2005]   [Oct]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: 2.6.14-rc5-rt6 -- False NMI lockup detects

* Steven Rostedt <rostedt@goodmis.org> wrote:

> Hi Ingo and Thomas,
>
> On some of my machines, I've been experiencing false NMI lockups.
> This usually happens on slower machines, and taking a look into this,
> it seems to be due to a short time where no processes are using
> timers, and the ktimer interrupts aren't needed. So the APIC timer,
> which now is used only for the ktimers, has a five second pause, and
> causes the NMI to go off. The NMI uses the apic timer to determine
> lockups.

this would be a bug - the jiffy tick should be processed every 1 msec,
regardless of whether there are any ktimers pending. (in the future we
want to use a special ktimer for the jiffy tick, but that's not
implemented yet.)

> So, I added a more generic method. This only works for x86 for now,
> but it has a #ifdef to keep other archs working until it implements
> this as well. I added a nmi_irq_incr which is called by __do_IRQ in
> the generic code. This is what is used in the NMI code to determine
> if the CPU has locked up. This way we don't have to worry about what
> resource we are using for timers.

this will be useful for tickless stuff - but right now 'no APIC timer
irq for 5 seconds' is a 'must not happen'.

Ingo
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-10-25 16:31    [W:0.075 / U:0.240 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site