Re: [PATCH] ACPI/CPUIDLE: prevent setting pm_idle to NULL

[Andi Kleen <andi@firstfloor.org>]

> The problem here is that the acpi/cpuidle code can be in a state where
> the _save/old variables _ARE_ NULL because they had not been
> initialized with the original pm_idle before the module is removed or
> the cst state changes. So all we have to do is to prevent pm_idle to
> be set to NULL.

It still seems wrong to me to fall back to the cpuidle idle function
instead of the earlier idle function just because cpuidle was loaded
in a weird way. 

But yes mwait_idle could be set up later after the saving state.
I suggested default_idle because it is safe, but yes it is probably
not the optimal choice.

Perhaps to solve this cleanly we really need to go to a hierarchy
of idle functions registered with priority instead of this fragile
pointer saving/restoring. 

-Andi