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

[Hans Petter Selasky]

On 2020-04-08 01:23, Mark Johnston wrote:
> On Mon, Apr 06, 2020 at 02:34:50PM -0700, Eric Joyner wrote:
>> On Mon, Apr 6, 2020 at 2:29 PM Mark Johnston <markj at freebsd.org> wrote:
>>
>>> On Mon, Apr 06, 2020 at 02:19:25PM -0700, Eric Joyner wrote:
>>>> Mark,
>>>>
>>>> I think I was mistaken about the backtrace looking the same. I was
>>> looking
>>>> at it from within ddb, and I think I focused on the
>>>> epoch_block_handler_preempt line and didn't notice that it only stopped
>>>> there this time. Here's the new one I've got from kgdb:
>>>
>>> Thanks.  Could you try to print "td->td_name" from frame 4?  It should
>>> also be available as er->er_blockedtd.  Basically, I'm trying to verify
>>> that the interrupt thread itself isn't the one that we're waiting for,
>>> else there is another bug to be fixed.
>>>
>>> If you can provide kernel symbols and vmcore, I'd be happy to look at it
>>> myself.
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>>
>> Here's what I get:
>>
>> (kgdb) frame 4
>> #4  epoch_block_handler_preempt (global=0xfffff80003de0100,
>> cr=0xfffffe00dee85900, arg=0x0) at /usr/src/sys/kern/subr_epoch.c:507
>> 507     }
>> (kgdb) print td->td_name
>> $1 = "if_io_tqg_31\000\000\000\000\000\000\000"
>> (kgdb) print er->er_blockedtd
>> $2 = (struct thread *) 0x0
> 
> 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?
> 

There is the same issue in kern_intr.c (FYI).

--HPS