linux-kernel - [PATCH] Driver core: fix refcounting bug

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Date:	Mon, 8 Jan 2007 11:06:44 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Greg KH <greg@...ah.com>, Kay Sievers <kay.sievers@...ell.com>
cc:	Kernel development list <linux-kernel@...r.kernel.org>
Subject: [PATCH] Driver core: fix refcounting bug

This patch (as832) fixes a newly-introduced bug in the driver core.
When a kobject is assigned to a kset, it must acquire a reference to
the kset.

Signed-off-by: Alan Stern <stern@...land.harvard.edu>

---

The bug was introduced in Kay's "unify /sys/class and /sys/bus at 
/sys/subsystem" patch.

I left the assignment of class_dev->kobj.parent as it was, although it is 
not needed.  The following call to kobject_add() will end up doing the 
same thing.

Alan Stern

P.S.: Tracking down refcounting bugs is a real pain!  I spent an entire 
afternoon on this one...  :-(


Index: usb-2.6/drivers/base/class.c
===================================================================
--- usb-2.6.orig/drivers/base/class.c
+++ usb-2.6/drivers/base/class.c
@@ -648,7 +648,7 @@ int class_device_add(struct class_device
 		class_dev->kobj.parent = &parent_class_dev->kobj;
 	else {
 		/* assign parent kset for uevent hook */
-		class_dev->kobj.kset = &parent_class->devices_dir;
+		class_dev->kobj.kset = kset_get(&parent_class->devices_dir);
 		/* the device directory in /sys/subsystem/<name>/devices */
 		class_dev->kobj.parent = &parent_class->devices_dir.kobj;
 	}

-
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