Andrew Morton wrote:
> Ingo Molnar <[email protected]> wrote:
> > - so buggy early bootup code which relies on interrupts being
> > off might be surprised by it.
>
> I don't think it's necessarily buggy that bootup code needs interrupts
> disabled. It _is_ buggy that bootup code which needs interrupts disabled
> is calling lock_cpu_hotplug().
I guess I don't understand -- why is it wrong for code that runs only
in early early bootup, when there is only one process context, to use
common code to e.g. register a hotplug cpu notifier? Should the
powerpc numa code be made to wait to register its notifier until
initcall time or something?
> > The fact that you observed that it's
> > somehow related to the timer interrupt seems to strengthen this
> > suspicion. DEBUG_MUTEXES=n on the other hand should have no such
> > interrupt-enabling effects.
> >
> > [ if this indeed is the case then i'll add irqs_off() checks to
> > DEBUG_MUTEXES=y, to ensure that the mutex APIs are never called with
> > interrupts disabled. ]
>
> Yes, I suppose so. But we're already calling might_sleep(), and
> might_sleep() checks for that. Perhaps the might_sleep() check is being
> defeated by the nasty system_running check.
Yes, which would be why this code never triggered a warning when
cpucontrol was a semaphore.
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