linux-kernel - Re: [PATCH] PCI: Fix racing for pci device removing via sysfs

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Date:	Mon, 29 Apr 2013 18:04:56 +0800
From:	Gu Zheng <guz.fnst@...fujitsu.com>
To:	Yinghai Lu <yinghai@...nel.org>
CC:	Bjorn Helgaas <bhelgaas@...gle.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] PCI: Fix racing for pci device removing via sysfs

Hi Yinghai,

On 04/27/2013 05:01 AM, Yinghai Lu wrote:

> On Fri, Apr 26, 2013 at 1:53 PM, Bjorn Helgaas <bhelgaas@...gle.com> wrote:
> 
>>
>> You can't be serious.  This is a disgusting mess.  Checking a list
>> pointer for LIST_POISON1?  As far as I'm concerned, this is a waste of
>> my time.
> 
> Well, then need to hold the bus ref, and check bus->devices list instead.

@@ -341,6 +352,7 @@ remove_store(struct device *dev, struct
 {
 	int err;
 	unsigned long val;
+	struct pci_dev *pdev;
 
 	if (strict_strtoul(buf, 0, &val) < 0)
 		return -EINVAL;
@@ -351,9 +363,14 @@ remove_store(struct device *dev, struct
 	/* An attribute cannot be unregistered by one of its own methods,
 	 * so we have to use this roundabout approach.
 	 */
+	pdev = pci_dev_get(to_pci_dev(dev));

There is no need to increase pci_dev's ref here, because we'll increase it 
in sysfs_schedule_callback.

+	get_device(&pdev->bus->dev);

So the pci_bus' ref management is still needed.
 
 	err = device_schedule_callback(dev, remove_callback);
-	if (err)
+	if (err) {
+		put_device(&pdev->bus->dev);
+		pci_dev_put(pdev);
 		return err;
+	}
 
 	return count;
 }

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