NMI during irq_interrupt() issue

Alexander Warg alexander.warg at os.inf.tu-dresden.de
Fri Aug 3 17:00:20 CEST 2007

On Fri, 2007-08-03 at 09:53 +0200, Stefan Scheler wrote:
> Hello,
> I implemented a statistical profiler for fiasco using performance
> monitoring counters (nmi handler is attached to handle_slow_trap()). It
> works fairly well for "mathematical" workloads but as soon as interrupt
> activity gets involved to a greater extent, the system freezes. For
> example, keeping a button pressed while sampling will freeze the machine
> within a few seconds. The NMI watchdog does not trigger during that
> freeze. Higher sampling rates also cause these freezes.
> So imho there seems to be a problem when irq_interrupt() or Irq::hit()
> is interrupted by an NMI. What do you think? Any hints on how to fix
> this or on how to debug this will be greatly appreciated.
> Thanks in advance. I will happily provide further information if needed.

I do'nt think tat there is a problem with an NMI in Fiasco's IRQ
routines, except that there may be stack overruns.

I'd suggest to use a task gate for your NMI and run it on a completely
different stack. Because there are parts of code that are extremely
sensible to NMIs and this is basically the sysenter path of the Fiasco

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