Subject: Re: [patch 06/10] Add notify die hooks and remove some redundant debugger hooks

From: Anton Blanchard <[email-masked]>
Date: Fri, 23 Mar 2007 09:09:29 -0500

Hi,

> As far as I can see, at the moment there is just one thing that gets
> registered to be called by die_notify, and that is
> kprobe_exceptions_notify.  It doesn't do anything with DIE_OOPS or
> DIE_MACHINE_CHECK.

Keep reading :) Later on I remove all the debugger() indirect branches.

> I would rather get rid of die_notify and have a kprobe_notify instead
> that just directly calls kprobe_exceptions_notify.  In fact having
> separate kprobe routines for the different events would be even
> better.
> 
> It's not like our cpus are particularly good at indirect functions
> calls... ;(

True and we are removing a set of indirect branches that exist already
(debugger). Id prefer not to have 2 sets of duplicate hooks for all this
stuff.

Keep in mind with xmon and kprobes disabled these calls are fast. I
verified it in sim after Christophs 300 cycle rant, a pessimistic
estimate is 20 cycles on power5, including function call overhead.

Anton