Re: [GIT PULL] PM updates for 2.6.33

Linus Torvalds
2009-12-06T00:52:32Z

On Sun, 6 Dec 2009, Rafael J. Wysocki wrote:
>
> > It all looks terminally broken: you force async suspend for all PCI
> > drivers, even when it makes no sense.
>
> I'm not exactly sure what you're referring to. The async suspend is not
> forced, it just tells the PM core that it can execute PCI suspend/resume
> callbacks in parallel as long as the devices in question don't depend on each
> other.

That's exactly what I mean by forcing async suspend/resume.

You don't know the ordering rules for PCi devices. Multi-function PCI
devices commonly share registers - they're on the same chip, after all.
And even when the _hardware_ is totally independent, we often have
discovery rules and want to initialize in order because different drivers
will do things like unregister entirely on suspend, and then re-register
on resume.

Imagine the mess when two ethernet devices randomly end up coming up with
different names (eth0/eth1) depending on subtle timing issues.

THAT is why we do things in order. Asynchronous programming is _hard_.
Just deciding that "all PCI devices can always be resumed and suspended
asynchronously" is a much MUCH bigger decision than you seem to have
even realized.

Linus