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From: Oliver Neukum <oliver@neukum.org>
To: Jiri Kosina <jkosina@suse.cz>
Subject: Re: Null Pointer BUG in uhci_hcd
Date: Tue, 7 Jul 2009 16:08:10 +0200
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Cc: "Michael S. Zick" <lkml@morethan.org>, linux-kernel@vger.kernel.org,
       linux-usb@vger.kernel.org
References: <200907051720.45819.lkml@morethan.org> <alpine.LRH.2.00.0907071111210.27150@twin.jikos.cz>
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Am Dienstag, 7. Juli 2009 11:13:01 schrieb Jiri Kosina:
> [ adding linux-usb to CC ]
>
> On Sun, 5 Jul 2009, Michael S. Zick wrote:
> > Anyone with suggestions about this one?

Looks like we should test for presence before we switch off
autosuspend for khubd. Please test this diagnostic patch if this is
repeatable.

	Regards
		Oliver

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 2af3b4f..c5b3929 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -371,11 +371,16 @@ static void kick_khubd(struct usb_hub *hub)
 {
 	unsigned long	flags;
 
-	/* Suppress autosuspend until khubd runs */
-	to_usb_interface(hub->intfdev)->pm_usage_cnt = 1;
+	if (!hub) {
+		BUG();
+		return;
+	}
 
 	spin_lock_irqsave(&hub_event_lock, flags);
 	if (!hub->disconnected && list_empty(&hub->event_list)) {
+		/* Suppress autosuspend until khubd runs */
+		to_usb_interface(hub->intfdev)->pm_usage_cnt = 1;
+
 		list_add_tail(&hub->event_list, &hub_event_list);
 		wake_up(&khubd_wait);
 	}
@@ -384,6 +389,11 @@ static void kick_khubd(struct usb_hub *hub)
 
 void usb_kick_khubd(struct usb_device *hdev)
 {
+	if (!hdev) {
+		BUG();
+		return;
+	}
+
 	/* FIXME: What if hdev isn't bound to the hub driver? */
 	kick_khubd(hdev_to_hub(hdev));
 }