Re: PROBLEM: Kernel 2.6.26 oops if I unplug my Logitech USB 1.1 headset

["Vegard Nossum" <vegard.nossum@gmail.com>]

On Fri, Sep 5, 2008 at 10:01 AM, Vegard Nossum <vegard.nossum@gmail.com> wrote:
> On Fri, Sep 5, 2008 at 9:58 AM, Vegard Nossum <vegard.nossum@gmail.com> wrote:
>> On Fri, Sep 5, 2008 at 9:09 AM, Takashi Iwai <tiwai@suse.de> wrote:
>>> At Thu, 4 Sep 2008 17:28:22 -0700,
>>> Andrew Morton wrote:
>>>>
>>>> On Fri, 05 Sep 2008 01:05:21 +0200
>>>> Edgar Kalkowski <eMail@edgar-kalkowski.de> wrote:
>>>>
>>>> > Dear kernel hackers. ;)
>>>> >
>>>> > [1.] One line summary of the problem: If I unplug my USB-Headset the kernel oopses.
>>>>
>>>> cc's added.
>>>>
>>>> Might be USB, might be ALSA.
>>>
>>> Hm, it's hard to guess...
>>> Edgar, could you check whether it happens with 2.6.25?
>>
>> Hi,
>>
>> I recognize this address:
>>
>>>>> BUG: unable to handle kernel paging request at 00100100
>>
>> Is this a magic value? I also got it, see for example:
>> http://lkml.org/lkml/2008/8/21/426
>>
>> Google will also recognize it:
>> http://www.google.com/search?hl=en&q="unable+to+handle+kernel+paging+request"+00100100
>>
>> Where does it come from?
>
> Oh. It _is_ LIST_POISON1. Sorry for the bit of noise.

Probably totally unrelated, but I couldn't help to find this bit of
code somewhat odd. In snd_ctl_dev_disconnect():

        down_read(&card->controls_rwsem);
        list_for_each_entry(ctl, &card->ctl_files, list) {
                wake_up(&ctl->change_sleep);
                kill_fasync(&ctl->fasync, SIGIO, POLL_ERR);
        }
        up_read(&card->controls_rwsem);

...shouldn't that be using &card->ctl_files_rwlock instead of
&card->controls_rwsem? That one is always used to protect the list ops
on &card->ctl_files in all the other places. Or maybe it is already
locked from higher ups?


Vegard

-- 
"The animistic metaphor of the bug that maliciously sneaked in while
the programmer was not looking is intellectually dishonest as it
disguises that the error is the programmer's own creation."
	-- E. W. Dijkstra, EWD1036