> On Sep 13, 2016, at 5:13 PM, Ben Pfaff <b...@ovn.org> wrote:
>
> On Tue, Sep 13, 2016 at 02:45:54PM -0700, Jarno Rajahalme wrote:
>>
>>> On Sep 13, 2016, at 10:56 AM, Ben Pfaff <b...@ovn.org> wrote:
>>>
>>> On Mon, Sep 12, 2016 at 01:52:31PM -0700, Jarno Rajahalme wrote:
>>>> Set ofproto's connmgr pointer to NULL after the connmgr has been
>>>> destructed, and check for NULL when sending a flow removed
>>>> notification.
>>>>
>>>> Verified by sending the flow removed message unconditionally and
>>>> observing numerous core dumps in the test suite.
>>>>
>>>> Found by inspection.
>>>>
>>>> Fixes: f695ebfae5 ("ofproto: Postpone sending flow removed messages.")
>>>> Signed-off-by: Jarno Rajahalme <ja...@ovn.org>
>>>> ---
>>>> v3: New patch for v3.
>>>
>>> I'm worried a bit that the rules needed to access these structures
>>> correctly are getting complicated. Maybe there should be a high-level
>>> overview somewhere.
>>>
>>
>> The main complication here is that if we tagged connmgr * with
>> OVS_GUARDED_BY(ofproto_mutex), we would need to do widen the scope of
>> ofproto_mutex quite a bit. Maybe introducing a rwlock for connmgr separately
>> would do it, albeit with the assumption that the main thread remains the
>> only writer, all that extra read locking from the main thread would be new
>> overhead. It would be more maintainable, though.
>
> Yes, I recognize that and I don't want to make the scope bigger if we
> can avoid it.
>
> Another option might be to just stick the flow_removed messages on a
> list from the callback and then flush them later in the ofproto_run()
> loop. They're already asynchronous and unpredictable since RCU can
> delay sending them an arbitrary amount of time.
>
Even that would have to deal with ofproto disappearing, but I like it as it
would simplify locking requirements. I’ll make a note to look at this later.
>> I made a note to look into this later.
>>
>> Do you think we should apply this to branch-2.6 as well as the master?
>
> It fixes a crash bug right? So, yes, unless you know a simpler fix.
I back ported this to 2.6.
Jarno
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