Issue with epoch_drain_callbacks and unloading iavf(4) [using iflib]

[Eric Joyner]

On Thu, Apr 9, 2020 at 2:29 PM Eric Joyner <erj at freebsd.org> wrote:

> On Thu, Apr 9, 2020 at 2:02 PM Eric Joyner <erj at freebsd.org> wrote:
>
>> On Tue, Apr 7, 2020 at 4:24 PM Mark Johnston <markj at freebsd.org> wrote:
>>
>>> I spent some time looking at the core.  It looks like we have yet
>>> another problem: the gtaskqueue code won't exit the net epoch if it is
>>> constantly running a net task.  Could you please retry with the patches
>>> from before, and this one included?
>>>
>>> diff --git a/sys/kern/subr_gtaskqueue.c b/sys/kern/subr_gtaskqueue.c
>>> index f52f32204644..2b1386a612ee 100644
>>> --- a/sys/kern/subr_gtaskqueue.c
>>> +++ b/sys/kern/subr_gtaskqueue.c
>>> @@ -345,7 +345,7 @@ gtaskqueue_run_locked(struct gtaskqueue *queue)
>>>         struct epoch_tracker et;
>>>         struct gtaskqueue_busy tb;
>>>         struct gtask *gtask;
>>> -       bool in_net_epoch;
>>> +       bool in net_epoch;
>>>
>>>         KASSERT(queue != NULL, ("tq is NULL"));
>>>         TQ_ASSERT_LOCKED(queue);
>>> @@ -361,20 +361,19 @@ gtaskqueue_run_locked(struct gtaskqueue *queue)
>>>                 TQ_UNLOCK(queue);
>>>
>>>                 KASSERT(gtask->ta_func != NULL, ("task->ta_func is
>>> NULL"));
>>> -               if (!in_net_epoch && TASK_IS_NET(gtask)) {
>>> -                       in_net_epoch = true;
>>> +               if (TASK_IS_NET(gtask)) {
>>>                         NET_EPOCH_ENTER(et);
>>> -               } else if (in_net_epoch && !TASK_IS_NET(gtask)) {
>>> +                       in_net_epoch = true;
>>> +               }
>>> +               gtask->ta_func(gtask->ta_context);
>>> +               if (in_net_epoch) {
>>>                         NET_EPOCH_EXIT(et);
>>>                         in_net_epoch = false;
>>>                 }
>>> -               gtask->ta_func(gtask->ta_context);
>>>
>>>                 TQ_LOCK(queue);
>>>                 wakeup(gtask);
>>>         }
>>> -       if (in_net_epoch)
>>> -               NET_EPOCH_EXIT(et);
>>>         LIST_REMOVE(&tb, tb_link);
>>>  }
>>>
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>>
>> Yeah, I'll give it a spin and try to get back to you before the end of
>> the week.
>>
>> - Eric
>>
>
> I was able to try it out just now, and it looks this (and all of the other
> patches) finally causes the problem to not appear! I can unload the driver
> while iavf1 is receiving heavy traffic!
>
> - Eric
>

  Hi Mark,

Are you planning to commit these patches to HEAD? I see the reviews for
D24214 and D24215 are still up, and I don't know if you created a review
for the patch you put in this email chain.

- Eric