[ovs-dev] [PATCH ovn v2 0/9] Incremental processing for flow installation.

Dumitru Ceara dceara at redhat.com
Mon Sep 14 13:03:42 UTC 2020

On 9/11/20 9:16 PM, Dumitru Ceara wrote:
> On 9/11/20 8:39 PM, Han Zhou wrote:
>> On Fri, Sep 11, 2020 at 6:17 AM Dumitru Ceara <dceara at redhat.com
>> <mailto:dceara at redhat.com>> wrote:
>>> On 9/9/20 11:13 PM, Han Zhou wrote:
>>>> On Wed, Sep 9, 2020 at 6:39 AM Mark Michelson <mmichels at redhat.com
>> <mailto:mmichels at redhat.com>> wrote:
>>>>> Thanks for addressing my concerns on patch 9.
>>>>> Acked-by: Mark Michelson <mmichels at redhat.com
>> <mailto:mmichels at redhat.com>>
>>>>> Warning: I'm also ACKing Numan's patch series that also adds some
>>>>> lflow-level caching (but he is caching expressions). So whoever loses
>>>>> this merge race may have some work to do in order to apply their patch
>>>>> cleanly.
>>>> Thanks Mark for the review, and the warning :).
>>>> I applied the series to master, and also the first 4 patches to
>>>> branch-20.06 and patch 1,2,4 to branch-20.03, to fix the conjunction
>> flow
>>>> bug in those branches.
>>>> Thanks,
>>>> Han
>>> Hi Han,
>>> This seems to cause an assertion failure in ovn-controller compiled with
>>> today's OVS/OVN master branches. I'm not completely sure about the steps
>>> to reproduce because I was testing some other ovn-k8s related things but
>>> I did get a core dump and the NB/DB/conf DBs.
>>> I opened a RedHat BZ [0] (more for my tracking than anything else) and I
>>> shared there the OVS/OVN revisions and how to build the exact same image
>>> that I was running when I hit the crash.
>>> I'll try to investigate what's happening but you're probably more
>>> familiar with the code so any hints would be great.
>>> Thanks,
>>> Dumitru
>>> [0] https://bugzilla.redhat.com/show_bug.cgi?id=1878139
>> Thanks Dumitru for reporting the issue. I reviewed the code and the test
>> cases again, and didn't figure out any problem yet. The failed assertion
>> "ovs_list_is_empty(&f->list_node) " is to assert that the desired_flow
>> is not accessed more than once in a single flood_remove call. This
>> should be true because the loop at
>> (https://github.com/ovn-org/ovn/blob/master/controller/ofctrl.c#L1126-L1134)
>> ensures that all flows in to_be_removed (which is the only list that
>> uses the "list_node" member) is detached from the cross reference lists,
>> so that in the following recursive calls these flows will never be
>> accessed again. Now that this assert fails, it could be some orphaned
>> pointer somewhere, leading to the "f" pointing to a flow that's already
>> destroyed.
>> One thing not clear to me is the version you used for the testing. In BZ
>> you mentioned revision: 520189bf313054702f5f802acd7944cca3b6baaa.
>> However, in this revision, the line number of the assertion doesn't
>> match the one you pasted in BZ. What you pasted was 1135:
> The revision should be good, I think the problem is with the way I
> rebuilt the packages in the new container after I retrieved the core dump.
> The assert message clearly points to line 1108. This is from the old
> logs of the run where I saw the crash:
> 2020-09-11T11:53:18.426Z|00037|util|EMER|controller/ofctrl.c:1108:
> assertion ovs_list_is_empty(&f->list_node) failed in
> flood_remove_flows_for_sb_uuid()
>> #6  0x00005607d73502fa in flood_remove_flows_for_sb_uuid
>> (flow_table=flow_table at entry=0x5607d8c4b380,
>> sb_uuid=sb_uuid at entry=0x5607d8f91430,
>> flood_remove_nodes=flood_remove_nodes at entry=0x7ffeccadb9c0) at
>> controller/ofctrl.c:1135
>> What's in the code for revision (520189bf) is 1108:
>> https://github.com/ovn-org/ovn/blob/520189bf313054702f5f802acd7944cca3b6baaa/controller/ofctrl.c#L1108
>> Did you change anything while doing the testing?
> I'll try to replicate the issue again next week, maybe we get more info.
> Thanks,
> Dumitru

Hi Han,

I managed to minimize the way to replicate the crash (with OVN master).
I do:

make sandbox
ovn-nbctl ls-add ls
ovn-nbctl lsp-add ls vm1
ovn-nbctl acl-add lsp-set-addresses vm1 "0a:58:fc:09:1d:4e fd00:10:244:1::5"
ovn-nbctl lsp-set-addresses vm1 "0a:58:fc:09:1d:4e fd00:10:244:1::5"
ovn-nbctl lsp-set-port-security vm1 "0a:58:fc:09:1d:4e fd00:10:244:1::5"
ovs-vsctl add-port br-int vm1 -- set interface vm1 type=internal -- set
interface vm1 external-ids:iface-id=vm1
sleep 1
ovs-vsctl set interface vm1 external-ids:iface-id=foo
sleep 1
ovs-vsctl set interface vm1 external-ids:iface-id=vm1
sleep 1
ovs-vsctl set interface vm1 external-ids:iface-id=foo

This crashes ovn-controller and if I look at the openflows before the
last port unbind, I notice some weird flows with action:


This looks broken. I tried to figure out what's happening but
unfortunately I didn't manage to.

Hope this helps pinpoint the root cause.


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