linux-kernel - Re: [PATCH][tentative] PCI / ACPI: Rework PCI host bridge removal to avoid sysfs warnings

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Message-ID: <6023795.zgEUjY5fWb@vostro.rjw.lan>
Date:	Tue, 31 Dec 2013 22:03:33 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Linux PCI <linux-pci@...r.kernel.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH][tentative] PCI / ACPI: Rework PCI host bridge removal to avoid sysfs warnings

On Tuesday, December 31, 2013 10:45:46 AM Yinghai Lu wrote:
> On Mon, Dec 30, 2013 at 5:15 AM, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
> > On Monday, December 30, 2013 01:51:28 PM Rafael J. Wysocki wrote:
> >> > We have patches that need to stop ioapic and iommu between
> >> > pci_stop_root_bus and pci_remove_root_bus.
> >
> > BTW, what *exactly* do they need to be stopped between?  After these two patches:
> 
> need to stop regular pci drivers before stop "driver" for ioapic/dmar.
> 
> >
> >> > Please check if the problem still happen after
> >> >
> >> > http://git.kernel.org/cgit/linux/kernel/git/helgaas/pci.git/patch/?id=c4a0a5d964e90b93eb4101c3927b788e083e530f
> >> >
> >> > http://git.kernel.org/cgit/linux/kernel/git/helgaas/pci.git/patch/?id=e3b439e1d315aff59c1b4f0fc43c5cd2d82b4138
> >
> > pci_stop_root_bus() is just a walk over devices on the root bus stopping
> > them and pci_remove_root_bus() starts with the removal of those devices.
> >
> > Surely, those two list walks can be combined into one?
> 
> maybe ok, but we have to problem to make sure stop pci drivers before
> "driver" for ioapic/dmar.

That's fine, but ioapic/dmar stopping need not happen between the stopping of
drivers and removing of devices on the root bus I suppose?

Actually, I think that the ioapic/dmar stopping should be carried out after
removing all of the root bus devices, or it can be racy with respect to a
driver reload.  Isn't that the case?

> also stop all first and remove all make it much cleaner.

Well, I don't think that's worth special casing, though, because device removal
may be triggered via sysfs anyway for any PCI device.  In my opinion it would
be cleaner to use pci_stop_and_remove_bus_device() everywhere for PCI device
removal.

> and add path is two steps too. Add them all, and then attach driver for all.

The removal need not mirror the probing ...

Thanks,
Rafael

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