Re: [PATCH] prevent sparc64 from invoking irq handlers on offlineCPUs

From: David Miller
Date: Tue Sep 09 2008 - 15:57:31 EST

From: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
Date: Tue, 09 Sep 2008 20:49:04 +0200

> David Miller wrote:
> > And IPI handler runs in HW irq context, therefore such an IPI-creates-an-IPI
> > should not be allowed, at least not directly.
> >
> > Actually the restriction seems to be that an IPI cannot be sent when
> > "irqs_disabled()", hmmm...
> >
> >
> Does this apply to smp_send_reschedule() as well?
> A [rare] codepath in the current rcu code does to trigger quiescent states on remote cpus.

It does work on sparc64. Such an IPI doesn't do a wait so there would
be no deadlock issues either.

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