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SubjectRe: Regression: BUG when battery is removed before resuming from hibernation
Rafael J. Wysocki wrote:
> On Tuesday 08 June 2010, Alan Jenkins wrote:
>
>> I found this bug 2.6.34 on my Asus EeePC 701 (x86_32 arch). It didn't
>> happen to me before, when I was running nearly-2.6.33 or 2.6.32-release.
>>
>> I used git-bisect, but unfortunately the result isn't very helpful. My
>> next step will be to try to narrowing down the culprits by disabling
>> individual CONFIG options. Here are my results so far, in case anyone
>> is interested.
>>
>>
>> == Steps to reproduce ==
>>
>> I) Boot off mains power, with battery removed. Login to KDE4 session,
>> with Konsole as the only running application.
>> II) Run "sudo pm-hibernate"
>>
>> 1. When the system switches to text mode (a.k.a the console),
>> immediately insert the battery.
>> 2. Once the system has fully hibernated, remove the battery.
>> 3. Press the power button to resume. The backtrace below is generated
>> during resume.
>>
>
> You're not supposed to be doing that.
>
> Rafael
>

I take it you mean "don't plug devices in during hibernation; you'll run
out of memory, Bad Things will happen, and you can expect resume to
fail". Pity. It wasn't an artificial test case, just an unusual usage
pattern of mine[1].

I guess it wouldn't be guaranteed safe even if I was plugging the device
in first. The battery connection could take a few seconds to stabilize,
and there's software equivalents in things like the usb-storage delay.

I can't complain about safety margins; other people might want to do
similar things with an entire docking station...

Any chance of a big screaming warning? IIRC there's one global flag to
fail userspace call-outs while userspace is frozen. Would it be
acceptable to document this in code & behaviour by aborting the
hibernation on hot-plug? (hot-*un*plug would presumably be allowed).

Alan


[1] I do this for conservation. I'm told batteries last longer if I
don't use them & let them get warm. I put the battery in for
hibernation so I can remove mains power without waiting. I start
hibernation first, because in practice you have to have the screen
closed in order to plug or unplug the battery.


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