On Feb 12, 2009, at 8:46 PM, Benjamin Herrenschmidt wrote:

On Thu, 2009-02-12 at 17:54 -0600, Kumar Gala wrote:

quoted

The e500mc supports the new msgsnd/doorbell mechanisms that were  
added in
the Power ISA 2.05 architecture.  We use the normal level doorbell  
for
doing SMP IPIs at this point.

Cool stuff. Haven't reviewed in details yet tho :-) But I was
thinking...

We should introduce a special xmon variant of local_irq_save/restore  
for
use by xmon that masks MSR:CE and use a crit doorbell for xmon IPI,  
that
would increase significantly the ability of xmon to catch deadlocked
CPUs, and we could use external CRITs as a more generic way of doing
IPIs, no ?

crit doorbell for xmon IPI sounds interesting.  However, I don't  
following about use of external CRITs for IPIs.

In fact, we should expose a local_crit_irq_save/restore (disable/ 
enable)
too for things like watchdog drivers etc... which may want to use  
these.

Yeah, probably a good thing for us to add.

- k