Re: [RFC/PATCH] usb/xhci: avoid kernel panic on xhci_suspend()

[Mathias Nyman]

On 01/08/2014 09:53 PM, David Cohen wrote:
> On Wed, Jan 08, 2014 at 10:48:06AM -0500, Alan Stern wrote:
> > On Tue, 7 Jan 2014, Greg KH wrote:
> >
> > > On Tue, Jan 07, 2014 at 05:44:26PM -0800, David Cohen wrote:
> > > > From: jianqian <jianqiang.tang@xxxxxxxxx>
> > > >
> > > > There is a possible kernel panic faced on xhci_suspend().
> > > > Due to kernel modified the hub autosupend_delay to 0s, after usb1 root
> > > > hub finishes initialization, it will trigger runtime_suspend and then
> > > > it will trigger xhci runtime suspend. But at that time, if
> > > > xhci->shared_hcd is still doing initialization, it is possible to face
> > > > null pointer kernel panic in xhci_suspend() function.
> > > >
> > > > This patch checks if xhci->shared_hcd is null to avoid panic.
> > >
> > > That sounds like this is a race that should be fixed properly, not just
> > > papered over, right?
> >
> > That was my reaction too.  The best way to solve the problem is to
> > prevent the USB-2 root hub from suspending until after the USB-3 root
> > hub has been registered.
>
> That makes sense. Thanks for the feedback.
> I'll check for a new approach.

Could you check if this patch works for you?:

http://marc.info/?l=linux-usb&m=139298822514995&w=2

I'm not able to reproduce the original issue myself

-Mathias
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