netdev - Re: That's pretty much it for 3.5.0

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Date:	Tue, 17 Jul 2012 12:17:32 -0700
From:	John Fastabend <john.r.fastabend@...el.com>
To:	"Rustad, Mark D" <mark.d.rustad@...el.com>
CC:	David Miller <davem@...emloft.net>,
	"<netdev@...r.kernel.org>" <netdev@...r.kernel.org>,
	"<linux-wireless@...r.kernel.org>" <linux-wireless@...r.kernel.org>,
	"<netfilter-devel@...r.kernel.org>" <netfilter-devel@...r.kernel.org>
Subject: Re: That's pretty much it for 3.5.0

On 7/17/2012 12:09 PM, John Fastabend wrote:
> On 7/17/2012 12:00 PM, John Fastabend wrote:
>> On 7/17/2012 11:48 AM, Rustad, Mark D wrote:
>>> On Jul 17, 2012, at 10:41 AM, Rustad, Mark D wrote:
>>>
>>>> On Jul 17, 2012, at 9:01 AM, David Miller wrote:
>>>>
>>>>> Linus was _extremely_ generous and took in all the stuff that was
>>>>> pending in the net tree just now.
>>>>
>>>> Maybe *too* generous. :-) I just updated and when I boot I get an
>>>> early crash in update_netdev_tables which is in netprio_cgroup.c.
>>>>
>>>>> Besides very serious issues, I'm not willing to consider any more bug
>>>>> fixes for the 'net' tree at this time.
>>>>
>>>> I think the above issue will have to be fixed, as it completely
>>>> prevents booting for any kernel that includes the netprio_cgroup
>>>> option.
>>>>
>>>>> Only one pending known bug qualifies, and that's the CIPSO ip option
>>>>> processing OOPS'er.  And I'll work on that myself if Paul Moore
>>>>> doesn't show a sign of life in the next day.
>>>>>
>>>>> Thanks.
>>>>
>>>>
>>>> I can start taking a look at this if you like, but I see that Gao
>>>> feng has two patches in the last set of patches that may be related.
>>>>
>>>> To give you an idea how early the crash is, here are a few log
>>>> messages leading up to it:
>>>>
>>>> [    0.003455] Dentry cache hash table entries: 262144 (order: 9,
>>>> 2097152 bytes)
>>>> [    0.005550] Inode-cache hash table entries: 131072 (order: 8,
>>>> 1048576 bytes)
>>>> [    0.007165] Mount-cache hash table entries: 256
>>>> [    0.010289] Initializing cgroup subsys net_cls
>>>> [    0.010947] Initializing cgroup subsys net_prio
>>>> [    0.011039] BUG: unable to handle kernel NULL pointer dereference
>>>> at 0000000000000828
>>>> [    0.011998] IP: [<ffffffff814202c8>] update_netdev_tables+0x68/0xe0
>>>
>>>
>>> I found that I can avoid the crash by configuring the netprio_cgroup
>>> as a module. I don't need to have it built in, I just happened to.
>>> This finding may lower the temperature of this issue a lot from what I
>>> had been feeling.
>>>
>>
>> hmm looks like we access init_net here,
>>
>> static void update_netdev_tables(void)
>> {
>>          struct net_device *dev;
>>          u32 max_len = atomic_read(&max_prioidx) + 1;
>>          struct netprio_map *map;
>>
>>          rtnl_lock();
>>          for_each_netdev(&init_net, dev) {
>>                  map = rtnl_dereference(dev->priomap);
>>                  if ((!map) ||
>>                      (map->priomap_len < max_len))
>>                          extend_netdev_table(dev, max_len);
>>          }
>>          rtnl_unlock();
>> }
>>
>> but inet_net is initialized by pure_initcall(net_ns_init) and I
>> gather pure_initcall's should not have any dependencies but it
>> looks like we created one here with cgroup_init_early() in
>> start_kernel().
>>
>> I'll poke around some more. Also had some off list help from
>> Mark.
>>
>> .John
>>
>
> although we don't have an early_init hook for netprio_cgroup so this
> is probably not correct.

Hey Mark,

you have better timing then me (I can't make this fail). Can you try
cgroup_init below rest_init() in start_kernel(). That's in init/main.c

.John

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