Re: Ottawa Linux Power Management Summit, June 25-26, 2007 - Minutes

Thomas Gleixner
2007-09-25T12:00:41Z

On Tue, 2007-09-25 at 13:39 +0200, Rafael J. Wysocki wrote:
> On Monday, 24 September 2007 21:41, Dave Jones wrote:
> > On Sun, Sep 09, 2007 at 02:26:39PM +0200, Rafael J. Wysocki wrote:
> >
> > > > Dave mentioned that Fedora Core 7 32-bit is now shipping with
> > > > CONFIG_NOHZ=y and CONFIG_HZ=1000.
> > >
> > > CONFIG_NOHZ is known to break suspend and resume on some machines. These
> > > problems are being fixed over time, but that's a risky decision for a
> > > distribution to switch it on by default.
> >
> > Expect to see everyone else doing the same thing in the next versions.
> > Without field-testing this stuff it remains busted. A lot of bugs got
> > found and fixed by having this in Fedora that weren't tripped over
> > by linux-kernel testers at all.
>
> Well, that's certainly true.
>
> Still, we have open suspend bugs in which NO_HZ appears to be the culprit,
> eg. http://bugzilla.kernel.org/show_bug.cgi?id=8680

Grr, kernel.org bugzilla is down. I take a look later.

Btw. I got an interesting private response to the latest ACPI fixes:

> > ACPI: disable lower idle C-states across suspend/resume
> >
> > Finally, the weird suspend/resume behavior of my Dell-420 laptop has
> > disapeared (no way to adjust brightness after a suspend when not in the
> > docking station). It was always dark after a resume and made the laptop
> > unuseable in practice.
>
> I cheered too early:
> I just discovered that suspending to ram works well for the first time,
> but after that it's still the same problem. Suspend to disk always
> worked well btw. But somehow there is a difference now: when switching
> to a normal console (ctrl-alt-F1 e.g.) and switching back to X the
> brightness works again. Another thing: I now can also suspend *in* the
> docking station, take it *out* and resume without problems, which never
> worked before :)

Len, did you / Venki look into a similar solution for cpuidle yet ? I'd
like to update -hrt ASAP. If not I just hack it in for now.

tglx