On Tue, Jul 3, 2018 at 3:51 PM Lukas Wunner <lukas@xxxxxxxxx> wrote:
>
> On Tue, Jul 03, 2018 at 02:50:40PM +0800, Pingfan Liu wrote:
> > commit 52cdbdd49853 ("driver core: correct device's shutdown order")
> > places an assumption of supplier<-consumer order on the process of probe.
> > But it turns out to break down the parent <- child order in some scene.
> > E.g in pci, a bridge is enabled by pci core, and behind it, the devices
> > have been probed. Then comes the bridge's module, which enables extra
> > feature(such as hotplug) on this bridge. This will break the
> > parent<-children order and cause failure when "kexec -e" in some scenario.
> >
> > The detailed description of the scenario:
> > An IBM Power9 machine on which, two drivers portdrv_pci and shpchp(a mod)
> > match the PCI_CLASS_BRIDGE_PCI, but neither of them success to probe due
> > to some issue. For this case, the bridge is moved after its children in
> > devices_kset. Then, when "kexec -e", a ata-disk behind the bridge can not
> > write back buffer in flight due to the former shutdown of the bridge which
> > clears the BusMaster bit.
>
> If you revert commit cc27b735ad3a ("PCI/portdrv: Turn off PCIe services
> during shutdown"), does the issue go away?
Yes, it is gone.
