Re: [uml-devel] uml_net zombie processes

[Richard Weinberger <richard@nod.at>]

Am 13.07.2015 um 15:58 schrieb Thomas Meyer:
> Am Montag, den 13.07.2015, 15:52 +0200 schrieb Richard Weinberger:
>> On Mon, Jul 13, 2015 at 3:41 PM, Thomas Meyer <thomas@m3y3r.de> 
>> wrote:
>>> Hi,
>>>
>>> The uml_net network setup "fails" on my computer with:
>>>
>>> [   15.930000] helper_wait : waitpid process 11673 failed, errno = 
>>> 10
>>> [   15.930000] * modprobe tun
>>>                * ifconfig tap0 192.168.10.1 netmask 255.255.255.255 
>>> up
>>>                * bash -c echo 1 > /proc/sys/net/ipv4/ip_forward
>>> [   20.480000] helper_wait : waitpid process 11780 failed, errno = 
>>> 10
>>> [   20.480000] * route add -host 192.168.10.2 dev tap0
>>>                * bash -c echo 1 >
>>> /proc/sys/net/ipv4/conf/tap0/proxy_arp
>>>
>>> because I run uml linux as a normal user and I guess these commands
>>> fail, because of insufficient rights:
>>> bash -c echo 1 > /proc/sys/net/ipv4/ip_forward
>>> bash -c echo 1 > /proc/sys/net/ipv4/conf/tap0/proxy_arp
>>>
>>> But this failure is okay for me, as firewalld, sets above options
>>> correctly on my host computer.
>>>
>>> The problem I see is that UML list two zombie processes:
>>>   11780 root       20   0     0     0     0 Z  0.0  0.0  0:00.00 
>>> 15:34 │  │     ├─ uml_net
>>>   11673 root       20   0     0     0     0 Z  0.0  0.0  0:00.00 
>>> 15:34 │  │     ├─ uml_net
>>>
>>> UML seems to never reap those two processes, likely because of 
>>> errno=10 exit code.
>>>
>>> any idea how to fix this?
>>
>> Hmm, it tries to reap them using waitpid().
>> But it seems to fail with ECHILD.
>>
>> Can you add a few prints to compare the PIDs?
> 
> Sure, where should I add those?
> os-Linux/helper.c - helper_wait(int pid) ?

Yeah. And please add a dump_stack() to figure out where it was called.

Thanks,
//richard

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