Re: Linux 3.7-rc3

[Alan Stern]

On Fri, 2 Nov 2012, Linus Torvalds wrote:

> On Fri, Nov 2, 2012 at 3:43 PM, Rafael J. Wysocki <rjw@xxxxxxx> wrote:
> >
> > Well, not everything is rosy in the suspend land, though.  This is a
> > failure to freeze khubd during the second in a row attempt to suspend to
> > RAM (your current tree):
> 
> Ugh. So khubd is blocked in usb_start_wait_urb(), and apparently the
> timeout for that block is longer than the freezing timeout.
> 
> There's a comment about why khubd needs to be freezable, but I wonder
> if that whole thing isn't doing something wrong. Causing the suspend
> to fail is definitely always the wrong thing.

khubs has been a potential problem for suspend since the beginning.

The USB spec mandates timeouts of 5 seconds.  In addition, khubd does
lots of retries when errors occur (probably way too many) and checks
for freezability only when its to-do list is empty.

Under normal circumstances this isn't a problem.  Issues arise when a 
non-cooperative device is plugged in shortly before a suspend starts.

I suppose we could scatter a whole bunch of checks at spots throughout 
the device-initialization code.  This seems awkward but I can't think 
of anything better.  Does anyone have other suggestions?

Alan Stern

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