Re: [PATCH v3 1/1] xhci: Prevent runtime pm from autosuspending during initialization

[Sarah Sharp <sarah.a.sharp@linux.intel.com>]

On Tue, Mar 04, 2014 at 09:04:58AM -0800, Greg KH wrote:
> On Tue, Mar 04, 2014 at 01:50:55PM +0200, Mathias Nyman wrote:
> > On 03/03/2014 08:37 PM, Greg KH wrote:
> > >On Mon, Mar 03, 2014 at 07:30:17PM +0200, Mathias Nyman wrote:
> > >>xHCI driver has its own pci probe function that will call usb_hcd_pci_probe
> > >>to register its usb-2 bus, and then continue to manually register the
> > >>usb-3 bus. usb_hcd_pci_probe does a pm_runtime_put_noidle at the end and
> > >>might thus trigger a runtime suspend before the usb-3 bus is ready.
> > >
> > >What is the result if that happens?
> > 
> > Crashes. Null pointer dereference in xhci_suspend() when touching
> > xhci->shared_hcd before it's initialized. More info here:
> > 
> > http://marc.info/?l=linux-usb&m=138914518219334&w=2
> > 
> > >
> > >Is this a regression from 3.13?  Or something new for 3.14?
> > >
> > 
> > According to reporter its been around since 3.7
> > 
> > commit 596d789a211d134dc5f94d1e5957248c204ef850
> > USB: set hub's default autosuspend delay as 0
> > 
> > But nobody else than the reporter is able to trigger it.
> 
> Then it can wait for 3.15-rc1, and then go back to the stable trees at
> that time, right?  I'd prefer that as it's not a regression and not
> common.

Ok, I'll queue it with the other features for 3.15.

Sarah Sharp