linux-kernel - Re: [PATCHv3 2/4] drivers/base: utilize device tree info to shutdown devices

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Message-ID: <CAFgQCTt0M=+AQKXFXcOkxppjnDK9EAyNxHN=2F+n_NvyN=rQqg@mail.gmail.com>
Date:   Tue, 3 Jul 2018 17:26:27 +0800
From:   Pingfan Liu <kernelfans@...il.com>
To:     lukas@...ner.de
Cc:     linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Grygorii Strashko <grygorii.strashko@...com>,
        Christoph Hellwig <hch@...radead.org>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Dave Young <dyoung@...hat.com>, linux-pci@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCHv3 2/4] drivers/base: utilize device tree info to shutdown devices

On Tue, Jul 3, 2018 at 3:51 PM Lukas Wunner <lukas@...ner.de> 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.