From mboxrd@z Thu Jan  1 00:00:00 1970
From: Chris Diamand <chris.diamand@arm.com>
Subject: Re: [PATCH] PM / devfreq: Don't delete sysfs group twice
Date: Thu, 15 Dec 2016 10:41:47 +0000
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To: Chanwoo Choi <cw00.choi@samsung.com>
Cc: Sudeep Holla <Sudeep.Holla@arm.com>, "linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>, MyungJoo Ham <myungjoo.ham@samsung.com>, Kyungmin Park <kyungmin.park@samsung.com>, Nishanth Menon <nm@ti.com>, Cai Zhiyong <caizhiyong@huawei.com>, "cpgs (cpgs@samsung.com)" <cpgs@samsung.com>

Hi!

> As you mentioned, it is right to remain this code in _remove_devfreq()
> for other case to unregister devfreq device except for devfreq_remove_device().

Sure, I'll send out another patch with a comment.

Although, if anyone does unregister devfreq without devfreq_remove_device(),
the userspace governor will still be broken.

I wonder if it would be better to fix this in the governor instead, because
this problem only affects things using sysfs entries. Something like this:

--- a/drivers/devfreq/governor_userspace.c
+++ b/drivers/devfreq/governor_userspace.c
@@ -112,7 +112,13 @@ out:
 
 static void userspace_exit(struct devfreq *devfreq)
 {
-	sysfs_remove_group(&devfreq->dev.kobj, &dev_attr_group);
+	/*
+	 * Remove the sysfs entry, unless this is being called after
+	 * device_del(), which should have done this already via kobject_del().
+	 */
+	if (devfreq->dev.kobj.sd)
+		sysfs_remove_group(&devfreq->dev.kobj, &dev_attr_group);
+
 	kfree(devfreq->data);
 	devfreq->data = NULL;
 }

It's a bit uglier, but would fix it in all cases - what do you think?

Cheers,
Chris