From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-ID: <5315BE1F.8020100@linux.intel.com> Date: Tue, 04 Mar 2014 13:50:55 +0200 From: Mathias Nyman MIME-Version: 1.0 To: Greg KH CC: linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, sarah.a.sharp@linux.intel.com, dan.j.williams@intel.com, stable@vger.kernel.org, David Cohen Subject: Re: [PATCH v3 1/1] xhci: Prevent runtime pm from autosuspending during initialization References: <1393867817-10389-1-git-send-email-mathias.nyman@linux.intel.com> <1393867817-10389-2-git-send-email-mathias.nyman@linux.intel.com> <20140303183733.GA13926@kroah.com> In-Reply-To: <20140303183733.GA13926@kroah.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: 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. > What platform(s) are affected by this? David, the reporter (added to cc), mentioned "This bug happened in a platform with 1 usb3 host controller + 1 usb3 OTG controller" run by some Intel internal group http://marc.info/?l=linux-usb&m=138915969822029&w=2 David, can you elaborate on the platform? >> xhci-platform driver is not using usb_hcd_pci_probe to set up >> busses and should not need to have it's usage count increased during probe. > > I didn't think we had any in-kernel users of the xhci-platform driver, > has that changed and I missed a new platform being added? > Not that I'm aware of. I just wanted to point out that this issue is only a matter on pci enumerated xhci hosts. -Mathias