Re: BUG: cpufreq notification broken

From: Thomas Gleixner
Date: Thu Nov 16 2006 - 16:34:14 EST


On Thu, 2006-11-16 at 16:26 -0500, Alan Stern wrote:
> On Thu, 16 Nov 2006, Thomas Gleixner wrote:
>
> > There is another issue with this SRCU change:
> >
> > The notification comes actually after the real change, which is bad. We
> > try to make the TSC usable by backing it with pm_timer accross such
> > states, but this behaviour breaks the safety code.
>
> I don't understand. Sending notifications is completely separate from
> setting up the notifier chain's head. The patch you mentioned didn't
> touch the code that sends the notifications.

Yeah, my bad. It just uses rcu based locking, but its still synchronous.

I have to dig deeper, why the change of the frequency happens _before_
the notifier arrives.

tglx


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