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

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Date:	Thu, 2 Jan 2014 14:47:04 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
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 Tue, Dec 31, 2013 at 1:03 PM, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
> 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?

No. It should be before removing all root bus devices.
as they need to access the pci devices during stop ioapic and dmar.

Also ioapic itself could one one pci device.

Yinghai
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