Re: [domU suspend/resume] Interrupts and event channel code

[Jean-Yves Migeon <jean-yves.migeon%espci.fr@localhost>]

Manuel Bouyer wrote:
> > Which basically removes the handler for xenstored wakeup() calls, in 
> > case xenbus_irq() != 0. Any code path I am not aware of, which 
> > manipulates the xenstored handler and xenbus_irq before xenbus attach? 
> > From my PoV, the event_remove_handler() will never be called here.
> >     
> I think it's related to suspend/resume, precisely. When xb_init_comms()
> is called again after a resume, the event channel may have changed, so
> you have to remove the old one before setting up a new one.
> Maybe on NetBSD it can be done in a different way.
>   
> > BTW, shouldn't the handler removal operation rather be part of a 
> > _detach() routine for xenbus?
> >     
> For suspend/resume you don't want to detach/reattach xenbus, because it'd
> also means to detach/reattach the child devices.
>   
Huh, I just noticed I was not clear on this point.

We have two possibilities here (as there are many parts elsewhere, like 
console, where we can do with two different ways):
1 - either check upon resuming that the event channels/parameters have 
changed, and update the values accordingly (done in the resume handler code)
2 - or invalidate them when calling suspend handlers, and reinstate them 
upon resume.

Option 2 looks cleaner to me. It would make sense to invalidate events 
associated to comms between dom0 and domUs at the same time (especially 
when we are detaching wd* block devices, for example).

--
Jean-Yves Migeon
jean-yves.migeon%espci.fr@localhost