On Sat, Nov 3, 2012 at 9:38 PM, Huang Ying <ying.huang@xxxxxxxxx> wrote: > On Sat, 2012-11-03 at 11:22 -0600, Bjorn Helgaas wrote: >> On Fri, Nov 2, 2012 at 11:06 PM, Huang Ying <ying.huang@xxxxxxxxx> wrote: >> > On Fri, 2012-11-02 at 10:50 -0600, Bjorn Helgaas wrote: >> >> On Wed, Oct 24, 2012 at 12:54 AM, Huang Ying <ying.huang@xxxxxxxxx> wrote: >> >> > If a PCI device and its parents are put into D3cold, unbinding the >> >> > device will trigger deadlock as follow: >> >> > >> >> > - driver_unbind >> >> > - device_release_driver >> >> > - device_lock(dev) <--- previous lock here >> >> > - __device_release_driver >> >> > - pm_runtime_get_sync >> >> > ... >> >> > - rpm_resume(dev) >> >> > - rpm_resume(dev->parent) >> >> > ... >> >> > - pci_pm_runtime_resume >> >> > ... >> >> > - pci_set_power_state >> >> > - __pci_start_power_transition >> >> > - pci_wakeup_bus(dev->parent->subordinate) >> >> > - pci_walk_bus >> >> > - device_lock(dev) <--- dead lock here >> >> > >> >> > >> >> > If we do not do device_lock in pci_walk_bus, we can avoid dead lock. >> >> > Device_lock in pci_walk_bus is introduced in commit: >> >> > d71374dafbba7ec3f67371d3b7e9f6310a588808, corresponding email thread >> >> > is: https://lkml.org/lkml/2006/5/26/38. The patch author Zhang Yanmin >> >> > said device_lock is added to pci_walk_bus because: >> >> > >> >> > Some error handling functions call pci_walk_bus. For example, PCIe >> >> > aer. Here we lock the device, so the driver wouldn't detach from the >> >> > device, as the cb might call driver's callback function. >> >> > >> >> > So I fixed the dead lock as follow: >> >> > >> >> > - remove device_lock from pci_walk_bus >> >> > - add device_lock into callback if callback will call driver's callback >> >> > >> >> > I checked pci_walk_bus users one by one, and found only PCIe aer needs >> >> > device lock. >> >> >> >> Is there a problem report or bugzilla for this issue? >> > >> > No. I found this issue when I developed kexec fixing. >> > >> > Best Regards, >> > Huang Ying >> > >> >> > Signed-off-by: Huang Ying <ying.huang@xxxxxxxxx> >> >> > Cc: Zhang Yanmin <yanmin.zhang@xxxxxxxxx> >> >> >> >> Should this go to stable as well? The D3cold support appeared in >> >> v3.6, so my guess is that this fix could go to v3.6.x. >> >> What about the stable tree? > > You are right. This fix should go to v3.6.x stable tree. I applied these two patches to my for-linus branch as v3.7 material. Thanks! -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
