Re: [regression, 2.6.37-rc1] 'ip link tap0 up' stuck in do_exit()

Jim Bos
2010-12-09T17:59:48Z

On 12/09/2010 05:47 PM, Américo Wang wrote:
> On Wed, Dec 08, 2010 at 03:08:22PM +0100, Oleg Nesterov wrote:
>> On 12/08, Oleg Nesterov wrote:
>>>
>>> On 12/08, Oleg Nesterov wrote:
>>>>
>>>> On 12/08, Florian Mickler wrote:
>>>>>
>>>>> [ ccing Ingo and Oleg ] as suggested
>>>>
>>>> Well. Of course I can't explain this bug. But, looking at this email
>>>> I do not see amything strange in exit/schedule/etc.
>>>>
>>>>>>>>>>> This is resulting in the command 'ip link set tap0 up' hanging as a zombie:
>>>>>>>>>>>
>>>>>>>>>>> root 3005 1 0 16:53 pts/3 00:00:00 /bin/sh /vm-images/qemu-ifup tap0
>>>>>>>>>>> root 3011 3005 0 16:53 pts/3 00:00:00 /usr/bin/sudo /sbin/ip link set tap0 up
>>>>>>>>>>> root 3012 3011 0 16:53 pts/3 00:00:00 [ip] <defunct>
>>>>
>>>> That is. ip is a zombie.
>>>
>>> And. I do not know if this matters or not, but "the command 'ip link
>>> set tap0 up' hanging as a zombie" does not look right.
>>>
>>> This was spawned by
>>>
>>>>>>>>> if [ -n "$1" ];then
>>>>>>>>> /usr/bin/sudo /sbin/ip link set $1 up
>>>>>>>>> sleep 0.5s
>>>>>>>>> /usr/bin/sudo /usr/sbin/brctl addif $switch $1
>>>>>>>>> exit 0
>>>>>>>>> fi
>>>
>>> The command does not hang. But it forks the child with pid == 3012,
>>> this child exits.
>>
>> Damn, sorry for noise, forgot to mention...
>>
>> The parent's trace (pid == 3011) can be more useful. Say, if it
>> hangs in do_wait(), then the kernel is obviously wrong.
>>
>
> Yeah, there is no point that a zombie can trigger a BUG_ON in kenrel.
> But it is still interesting to know why it becomes a zombie...
>
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ip link tap0 up not working might be this issue:

http://marc.info/?l=linux-netdev&m=128783852132311&w=2

( Latest Virtualbox 3.2.12 works around this issue )

Jim