Re: [perfmon2] probable solution for spinlock recursion bug on perfmon2 port to POWER5 during multiplexing test

[stephane e. <er...@go...>]

Corey,

On Jan 14, 2008 12:22 PM, Corey Ashford <cja...@us...> wrote:
> Stephane,
>
> What do you think is the right solution here?  Can you change the
> perfmon2 code such that the hrtimer call is not made in the event of a 0
> or negative relative time?
>
Looked at this some more on Friday. You cannot just drop the timeout because
you do need to call the handler to switch sets. I see 2 possibilities:
     - find a way to defer the hrtimer_start() until we are out of the
context switch
       code, i.e., like a signal handler
     - unlock the runqueue during switch_to().

I looked at the code in schedule() and the runqueue lock is not
grabbed once we come back
from switch_to(). That means that we can as well release it before
switch_to(). There is no
extra cost for doing this. I just need to make sure I understand why
this is not already done
today, like on IA-64. There are 2 separate controls, unmask irq,
unlock queue. We only
need the latter. I will ask on KML.