Re: USB regression: devices not initially recognized

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On Mon, 26 Oct 2009 22:31:16 -0400
eschvoca <eschvoca@xxxxxxxxx> wrote:

> Hi Oliver,
> 
> (Adding cc: Arjan)
> 
> On Wed, Oct 14, 2009 at 10:54 PM, eschvoca <eschvoca@xxxxxxxxx> wrote:
> > Hi Oliver,
> >
> > It ends up that the problem happens sporadically -- some reboots the
> > keyboard and bluetooth adapter don't work while other reboots it
> > does. I tried variations of reboot vs suspend vs shutdown vs unplug
> > power and couldn't find a repeatable pattern.  Perhaps the problem
> > is related to Ubuntu trying to speed up the boot process which
> > doesn't wait long enough for the USB devices to respond.  My mouse
> > always works while my USB bluetooth dongle and keyboard (through a
> > GASIA PS2toUSB Adapter) do not.
> >
> > I've been looking for a guide on how to do a "git bisect" on vanilla
> > kernels on ubuntu but haven't found anything that works well.  I
> > compiled a vanilla kernel but when I went to install the debs I was
> > warned that there already was a 2.6.28 kernel there and I would
> > overwrite it.  I would like to do a "git bisect" on the vanilla
> > kernel and be able to install them without conflicts.  Currently
> > the problem is showing up in about 25% of reboots.
> >
> > Please direct.
> >
> > Thanks.
> 
> After 16 bisects I tracked down the problem with my USB keyboard
> adapter and USB bluetooth dongle not initializing on boot-up to this
> commit:


my fear is the following: something ELSE in the system is missing a
synchronize_rcu(), and this case happened to save it by virtue of being
spurious.

Paul: do we call synchronize_rcu() before we go to userspace for the
first time somewhere?

Also.. in theory your X will get this sort of information from HAL, and
HAL will get it on demand as devices show up. I doubt Ubuntu has broken
that too much :)


-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org
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