[Xen-devel] RE: [PATCH v2 2/2] x86: don't unmask disabled irqs when migrating them

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Stefano Stabellini [mailto:stefano.stabellini@xxxxxxxxxxxxx]
> Sent: Friday, May 06, 2011 10:29 PM
> 
> On Fri, 6 May 2011, Tian, Kevin wrote:
> > > From: Thomas Gleixner
> > > Sent: Friday, May 06, 2011 6:00 PM
> > >
> > > On Fri, 6 May 2011, Tian, Kevin wrote:
> > > > x86: don't unmask disabled irqs when migrating them
> > > >
> > > > it doesn't make sense to mask/unmask a disabled irq when migrating
> > > > it from offlined cpu to another, because it's not expected to
> > > > handle any instance of it. Current mask/set_affinity/unmask steps
> > > > may trigger unexpected instance on disabled irq which then simply
> > > > bug on when there is no handler for it. One failing example is observed 
> > > > in
> Xen.
> > > > Xen pvops
> > >
> > > So there is no handler, why the heck is there an irq action?
> > >
> > >     if (!irq_has_action(irq) ....
> > >           continue;
> > >
> > > Should have caught an uninitialized interrupt. If Xen abuses
> > > interrupts that way, then it rightfully explodes. And we do not fix it by 
> > > magic
> somewhere else.
> >
> > sorry that my bad description here. there does be a dummy handler
> > registered on such irqs which simply throws out a BUG_ON when hit. I
> > should just say such injection is not expected instead of no handler.
> > :-)
> 
> I don't think this patch is necessary anymore after the event channel handling
> cleanup patches I have just sent to the list.
> Could you please try the following two patches:
> 
> http://marc.info/?l=linux-kernel&m=130468120032172&w=2
> http://marc.info/?l=linux-kernel&m=130468178200468&w=2
> 
> and let me know if you still need this patch?

thanks, and I'll take a look at them.

Thanks
Kevin

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