[ltp] apm and preemptive kernel patch

[Eric Jorgensen]

On Wed, 17 Jul 2002 23:10:47 +0200
Fabrice Planchon <fab@math.jussieu.fr> wrote:

> Hi,
> I was unable to get suspend/hibernate to work properly (on a 560X),
> with 2.4.18 and the preemptive kernel patch. Without it, it works
> fine. 
> Just looking around, I noticed somewhere some comments on the
> incompatibility between apm support and SMP support, and since the
> preemptive kernel patch utilizes SMP support, I guess it could come
> from that...

	That's probably not it. 

	The incompatibility between APM and SMP comes from the fact that the APM spec
wasn't written with SMP in mind - it only defines how to meddle with the first
processor in a system. Bad Things can happen if you try to go to sleep with two
processors, since hardware implementations vary and there isn't a standard. At
least, with APM there isn't. The ACPI spec does cover SMP power management.
Doesn't mean it works. 

	The preemptive kernel patch probably relies on spinlocks, which are part of how
the SMP kernel works. That wouldn't directly have anything to do with APM,
afaik. 

> so the question is: did anybody get it to work on a 2.4.* kernel ?
> what about the developpement kernels, since the preemptive kernel
> patch has been merged in recently ? did anybody manage to get
> preemption enabled with apm working at the same time ?

	They probably just accidentally broke APM when they implemented preemptability.
try asking the preempt people about it. 

 - eric

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