kern/112119: system hangs when starts k3b on RELENG_6

[Ganbold]

Thomas Quinot wrote:
> * Ganbold, 2007-04-25 :
>
>   
>>> Description:
>>>       
>> With atapi-cam.c (rev 1.42.2.3) when running k3b application, system
>> completely hangs on k3b splash screen and I had to use power button only
>> to restart the machine.
>>     
>
> Extremely strange. I can't offer any definite solution at this point,
> since I have no idea how this change could cause a system to hang. Here
> are a few possible investigation ideas:
>
> * AFAIK k3b is just a front-end for command-line tools. You should
>   determine what exact commands are spawned by k3b to identify which of
>   these is causing the apparent hang;
>
> * it would also be useful to enable CAM debugging options (see
>   "man 4 cam", option CAMDEBUG, and flags CAM_DEBUG_TRACE and
>   CAM_DEBUG_SUBTRACE) and to capture all console output up to the hang
>   (for example using a serial console)
>
> * if Scott's hunch of an interrupt storm is correct, then this issue
>   might be related to the DMA problem described under PR 103602, so
>   it would be useful to try the last patch I sent on that PR:
>   http://www.freebsd.org/cgi/query-pr.cgi?pr=103602&getpatch=12
>
> * if all else fails, please let me know if the attached patch, which
>   reverts part of rev. 1.42.2.3, changes anything.
>   

I will try http://www.freebsd.org/cgi/query-pr.cgi?pr=103602&getpatch=12 
patch later today
and let you know.

thanks,

Ganbold

> Thomas.
>
>