linux-kernel - Re: [BUG] usb/core/hub.c loops forever on resume from ram due to bluetooth

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Date:	Mon, 14 May 2007 19:48:02 -0400
From:	Mark Lord <lkml@....ca>
To:	Greg KH <gregkh@...e.de>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...l.org>, marcel@...tmann.org
Subject: Re: [BUG] usb/core/hub.c loops forever on resume from ram due to
 bluetooth

Greg KH wrote:
>
> Ok, I'll take a patch to keep the loop from going forever, but the main
> issue here is that there is probably a hardware failure somewhere.

Okay, found it.  The root cause here was a missing CONFIG_USB_SUSPEND=y,
which means the hci_usb device never got marked as USB_STATE_SUSPENDED,
which then caused the loop to go on forever.

The system works fine now with CONFIG_USB_SUSPEND=y in the .config.

Here's the patch to prevent future lockups for this or other causes.
I no longer need it, but it does still seem a good idea.

Signed-off-by:  Mark Lord <mlord@...ox.com>
---

--- old/drivers/usb/core/hub.c	2007-04-26 12:02:47.000000000 -0400
+++ linux/drivers/usb/core/hub.c	2007-05-01 18:48:46.000000000 -0400
@@ -403,9 +403,10 @@
 	struct usb_hub		*hub =
 		container_of(work, struct usb_hub, tt.kevent);
 	unsigned long		flags;
+	int			limit = 100;
 
 	spin_lock_irqsave (&hub->tt.lock, flags);
-	while (!list_empty (&hub->tt.clear_list)) {
+	while (--limit && !list_empty (&hub->tt.clear_list)) {
 		struct list_head	*temp;
 		struct usb_tt_clear	*clear;
 		struct usb_device	*hdev = hub->hdev;
-
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