[Fwd: Re: kern/118258 sysctl causing panics on 7.0-xxx]

Tai-hwa Liang avatar at mmlab.cse.yzu.edu.tw
Mon Jan 7 19:51:03 PST 2008

On Fri, 4 Jan 2008, John Baldwin wrote:
> On Friday 04 January 2008 05:19:28 am Tai-hwa Liang wrote:
>> On Thu, 3 Jan 2008, John Baldwin wrote:
>>> On Thursday 29 November 2007 10:53:32 pm Tai-hwa Liang wrote:
>>>> On Wed, 28 Nov 2007, Remko Lodder wrote:
>>>>> Hello,
>>>>> So as per Jeff's information, can someone from the -current
>>>>> list either contact jeff or try to resolve the problems
>>>>> mentioned? :)
>>>>    This is a longstanding bug which also exists in RELENG_6.  It turns
> out
>>>> that 'sysctl kern.ttys' after a terminal device is removed could trigger
>>>> this panic reliably.  For example, do 'sysctl kern.ttys' multiple times
>>>> after detaching an USB serial-to-rs232 cable or a PCMCIA modem card.
>>>>    Alternatively, following script would demo the panic if you don't have
>>>> a physically removable terminal device:
>>>> #!/bin/sh
>>>> #
>>>> # Warning! Running this script as root will panic your CURRENT box...
>>>> #
>>>> while true; do
>>>>  	kldload dcons
>>>>  	kldunload dcons
>>>>  	ls /dev
>>>>  	sysctl kern.ttys
>>>>  	sleep 1
>>>> done
>>>>    This seems to be a race between devfs and destroy_dev(), Cc'ing kib@
>>>> since he probably has more clues in this area.
>>> Try this patch.  Also available at
>>> http://www.FreeBSD.org/~jhb/patches/ttys_sysctl.patch
>>    With this patch, -CURRENT no longer boots and panics as follows:
> Fixed, was missing an unlock at the bottom of the loop.  Patch is updated at
> the same URL.

   This one works like a charm!  I've tried with USB-to-RS232 cable
as well as aforementioned script.  Now -CURRENT wouldn't panic by
dumping kern.ttys.

   Great work!


Tai-hwa Liang

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