* Darren Hart [off-list ref] [2010-08-04 21:45:51]:

On 07/23/2010 12:07 AM, Vaidyanathan Srinivasan wrote:

quoted

* Benjamin Herrenschmidt[off-list ref]  [2010-07-23 15:11:00]:

quoted

On Fri, 2010-07-23 at 10:38 +0530, Vaidyanathan Srinivasan wrote:

quoted

Yes.  extended_cede_processor() will return with interrupts enabled in
the cpu. (This is done by the hypervisor).  Under normal cases we
cannot be interrupted because no IO interrupts are routed to us after
xics_teardown_cpu() and since the CPU is out of the map, nobody will
send us IPIs.

What about decrementer ?

Decrementer expiry event handling is bit complex.  The event as such
may not bring back the extended_cede_processor() cpu, but may be
marked pending when we get out of this state eventually.  I will find
more information on this event and update.

Hi Vaidy, have you been able to dig anything up about the
decrementer expiry?

Hi Darren,

Yes, it is possible that the cpu in extended_cede_processor() can be
woken up by the decrementer.  But the expectation is that we will
return back to this context since we will not have any pending timers.

Our stack should not change even if we get the decrementer interrupts.

--Vaidy