linux-kernel - Re: Kernel oops with bluetooth usb dongle

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Date:	Fri, 22 Feb 2008 08:23:06 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Quel Qun <kelk1@...cast.net>
cc:	Dave Young <hidave.darkstar@...il.com>,
	Marcel Holtmann <marcel@...tmann.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Jiri Kosina <jkosina@...e.cz>, Ingo Molnar <mingo@...e.hu>
Subject: Re: Kernel oops with bluetooth usb dongle

Quel,

On Fri, 22 Feb 2008, Quel Qun wrote:
> $ addr2line -e vmlinux c012d51d
> /usr/src/linux-2.6.25-rc2-git5kk1/kernel/timer.c:770
> 
> Crap, that is on the next list_for_each_entry in timer.c :(
> 
> I tried to make a similar test loop as you did a few lines above:

Cool.
 
> I thought I got it on the next crash, but the system locked too
>  fast, and the only thing I saw was:
> 
> TTRACE timer f7b52858 fn f8e7c608 addr c012d776
> TTRACE fn l2cap_info_timeout
> TTRACE addr mod_timer
> BUG: unable to handle kernel paging request at 6b6b6b6b

That's what I wanted to see.
 
> I hope the tiny bit of trace can trigger some idea. At least l2cap
> has something to do with bluetooth. l2cap_info_timeout is line 360
> of net/bluetooth/l2cap.c, apparently only called from
> l2cap_conn_add, line 391: setup_timer(&conn->info_timer,
> l2cap_info_timeout, (unsigned long)conn);

Correct. And I don't see how it's guaranteed that the timer is deleted
before l2cap_conn_del() is called which kfree's the l2cap_conn
structure.

> After four hours and ten crashes today, it is the little I
> got. Kernel stuff is tough...

Yes, it is. The little information you got should be enough to solve
this. Thanks for your patience and help !

Does the patch below fix your problem ?

Thanks,

	tglx

---
 net/bluetooth/l2cap.c |    2 ++
 1 file changed, 2 insertions(+)

Index: linux-2.6/net/bluetooth/l2cap.c
===================================================================
--- linux-2.6.orig/net/bluetooth/l2cap.c
+++ linux-2.6/net/bluetooth/l2cap.c
@@ -417,6 +417,8 @@ static void l2cap_conn_del(struct hci_co
 		l2cap_sock_kill(sk);
 	}
 
+	del_timer(&conn->info_timer);
+
 	hcon->l2cap_data = NULL;
 	kfree(conn);
 }
--
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