"legacy" usb stack fixes
Julian Elischer
julian at elischer.org
Thu Sep 11 20:13:57 UTC 2008
Volker wrote:
> On 09/11/08 10:13, Hans Petter Selasky wrote:
>> On Monday 25 August 2008, Volker wrote:
>>> Anyway, I've already had those crashes even with the "new" usb stack
>>> (but it doesn't happen everytime - YMMV).
>>>
>> Hi,
>>
>> I also see crashes with my new stuff and the umass driver when the USB device
>> is un-plugged too early. The backtraces I've got so far does not indicate a
>> USB problem, though ....
>>
>> --HPS
>>
>
> // dropped current@ from CC
>
> Hans Petter,
>
> the device unplug problem is not just with usb, but these devices are
> the most frequent unplugged devices so far.
>
> Early this week, I discovered a new problem. I've fetched fresh RELENG_7
> sources, patched your usb stack in and recompiled kernel (using usb, not
> usb2).
>
> I've seen situations with a process holding open file descriptors for a
> ugen device being killed but a thread was still hanging in "usbdrain"
> state (sleeping on a mutex for draining). The process is still holding
> open file descriptors (I see output from ``fstat | grep ugen'' listing
> the already killed process), even while the process itself is already
> killed and not in the process list as a whole.
>
> Only a thread of that former process can be seen by ``ps -alxcH'', but
> it can't be killed.
what is the thread waiting on?
>
> I'm pretty sure I'm able to patch kern_exit.c to have that process being
> freed completely but I'm also pretty sure, this will just kill a symptom
> but not the source. While in that situation, the usb port does not react
> to plug/unplug events anymore.
>
> I haven't been able to debug that situation as I do have too much stress
> at other places as well. Probably I'll find the time tomorrow for debugging.
>
> BTW, can you give a quick explanation about usb2? What's different,
> better? What needs to be done at the driver side to port something over
> to usb2?
>
> Thanks,
>
> Volker
>
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