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

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Date:	Wed, 8 Jan 2014 15:41:52 -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 Mon, Jan 6, 2014 at 12:41 PM, Rafael J. Wysocki <rjw@...ysocki.net> wrote:

>> Not sure how that could happen.
>>
>> If it would really happen, we could set dev->match_driver to 0 in pci_stop_dev.
>
> Simply, run "modprobe -r driver && modprobe driver" in a loop and
> remove the PCI host bridge the given device is on in parallel to that.  Chances
> are, you'll see some nice breakage.

I would suggest using match_driver prevent driver from attaching again.

---
 drivers/pci/remove.c |    1 +
 1 file changed, 1 insertion(+)

Index: linux-2.6/drivers/pci/remove.c
===================================================================
--- linux-2.6.orig/drivers/pci/remove.c
+++ linux-2.6/drivers/pci/remove.c
@@ -11,6 +11,7 @@ static void pci_stop_dev(struct pci_dev
         pci_proc_detach_device(dev);
         pci_remove_sysfs_dev_files(dev);
         device_release_driver(&dev->dev);
+        dev->match_driver = false;
         dev->is_added = 0;
     }


>
> Also what happens if somebody uses the "remove" sysfs attribute on a device
> needed by ioapic/dmar?

Good question, we will have problem in that case.
To make it simple, we may hide the "remove" in sysfs for ioapic pci device ?

Thanks

Yinghai
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