Re: [PATCH -mm 2/2] PM: Disable usermode helper before hibernation and suspend

From: Rafael J. Wysocki
Date: Fri Jun 15 2007 - 17:30:55 EST

On Friday, 15 June 2007 15:08, Uli Luckas wrote:
> On Monday, 4. June 2007, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rjw@xxxxxxx>
> >
> > Use a hibernation and suspend notifier to disable the user mode helper
> > before a hibernation/suspend and enable it after the operation.
> >
> Hi Rafael,
> I have a couple of questions, regarding this patch ...
> > - if (!khelper_wq)
> > + if (!khelper_wq || usermodehelper_disabled)
> > return -EBUSY;
> 1) how about not returning -EBUSY here, if (wait == UMH_NO_WAIT)?

Yes, this would make sense.

> 2) how does your patch prevent wait_for_completion(&done) to hang during
> freezing if usermodehelper_pm_callback is called _after_ the above check?

It doesn't. Once the helper is running, we can't distinguish it from any other
user land process.

Still, it narrows the window quite a bit.


"Premature optimization is the root of all evil." - Donald Knuth
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