Subject: Re: reboot due to critical battery level
To: Jared D. McNeill <>
From: Steven M. Bellovin <>
List: tech-kern
Date: 12/20/2007 14:51:29
On Thu, 20 Dec 2007 14:27:39 -0500
"Jared D. McNeill" <> wrote:

> On 20-Dec-07, at 2:17 PM, Steven M. Bellovin wrote:
> >> Again, I suggest you actually look at powerd and pmf. You get ample
> >> warning before we force a shutdown, plenty of time to notify
> >> yourself before it reaches critical state.
> >
> > I have looked at powerd and parts of pmf.
> >>
> The problem with what you are suggesting is that depending on the age
> and condition of the battery, 5 minutes of runtime (or even 5 minutes
> of suspend time) may be too long. I have an older Powerbook that is
> on its second battery, where when it reports critical battery I only
> have about 20 seconds if I cancel the shutdown.

Been there, done that -- and if I were in that situation at the moment,
I'd indeed do something different.  Again, I'm not saying that your
solution is always wrong; I'm saying that it's not always right and I
need a choice, because preserving application-level integrity is often
just as important as preserving file system integrity.

Anyway -- the four of us have been over this several times, in private
and public.  I'd like to hear what others think, since it affects what
I'll write.
> Going forward, what we want to do on a critical battery condition is
> to suspend to disk, but we're not there yet.

		--Steve Bellovin,