cxgbe's native netmap support broken since r307394

[Luigi Rizzo]

On Wed, Dec 21, 2016 at 11:15 AM, Vincenzo Maffione
<v.maffione at gmail.com> wrote:
> Hi,
>   There is no commit related to that in the FreeBSD svn or git.
>
> The fix has been published to the github netmap repository here
> (branch master): https://github.com/luigirizzo/netmap
>
> What we should do is to import all the recent updates from the github
> into HEAD. I can prepare a patch for HEAD, if you wish. Just let me
> know.

I just checked and the diff between FreeBSD head and netmap head
in github is almost 3k lines due to a lot of recent refactoring.
So, if there is an easy way to extract just the locking change that would
be preferable as an interim solution.

cheers
luigi

>
> Cheers,
>   Vincenzo
>
>
> 2016-12-20 21:45 GMT+01:00 Adrian Chadd <adrian.chadd at gmail.com>:
>> hi,
>>
>> What's the commit? We should get it into -HEAD asap.
>>
>>
>> -adrian
>>
>>
>> On 20 December 2016 at 01:25, Vincenzo Maffione <v.maffione at gmail.com> wrote:
>>> Ok, applied to the netmap github repo.
>>> This fix will be published when Luigi does the next commit on FreeBSD.
>>>
>>> Cheers,
>>>   Vincenzo
>>>
>>> 2016-12-19 20:05 GMT+01:00 Navdeep Parhar <np at freebsd.org>:
>>>> IFNET_RLOCK will work, thanks.
>>>>
>>>> Navdeep
>>>>
>>>> On Mon, Dec 19, 2016 at 3:21 AM, Vincenzo Maffione <v.maffione at gmail.com> wrote:
>>>>> Hi Navdeep,
>>>>>
>>>>>   Indeed, we have reviewed the code, and we think it is ok to
>>>>> implement nm_os_ifnet_lock() with IFNET_RLOCK(), instead of using
>>>>> IFNET_WLOCK().
>>>>> Since IFNET_RLOCK() results into sx_slock(), this should fix the issue.
>>>>>
>>>>> On FreeBSD, this locking is needed to protect a flag read by nm_iszombie().
>>>>> However, on Linux the same lock is also needed to protect the call to
>>>>> the nm_hw_register() callback, so we prefer to have an "unified"
>>>>> locking scheme, i.e. always calling nm_hw_register under the lock.
>>>>>
>>>>> Does this make sense to you? Would it be easy for you to make a quick
>>>>> test by replacing IFNET_WLOCK with IFNET_RLOCK?
>>>>>
>>>>> Thanks,
>>>>>   Vincenzo
>>>>>
>>>>> 2016-12-17 23:28 GMT+01:00 Navdeep Parhar <np at freebsd.org>:
>>>>>> Luigi, Vincenzo,
>>>>>>
>>>>>> The last major update to netmap (r307394 and followups) broke cxgbe's
>>>>>> native netmap support.  The problem is that netmap_hw_reg now holds an
>>>>>> rw_lock around the driver's netmap_on/off routines.  It has always been
>>>>>> safe for the driver to sleep during these operations but now it panics
>>>>>> instead.
>>>>>>
>>>>>> Why is IFNET_WLOCK needed here?  It seems like a regression to disallow
>>>>>> sleep on the control path.
>>>>>>
>>>>>> Regards,
>>>>>> Navdeep
>>>>>>
>>>>>> begin_synchronized_op with the following non-sleepable locks held:
>>>>>> exclusive rw ifnet_rw (ifnet_rw) r = 0 (0xffffffff8271d680) locked @
>>>>>> /root/ws/head/sys/dev/netmap/netmap_freebsd.c:95
>>>>>> stack backtrace:
>>>>>> #0 0xffffffff810837a5 at witness_debugger+0xe5
>>>>>> #1 0xffffffff81084d88 at witness_warn+0x3b8
>>>>>> #2 0xffffffff83ef2bcc at begin_synchronized_op+0x6c
>>>>>> #3 0xffffffff83f14beb at cxgbe_netmap_reg+0x5b
>>>>>> #4 0xffffffff809846f1 at netmap_hw_reg+0x81
>>>>>> #5 0xffffffff809806de at netmap_do_regif+0x19e
>>>>>> #6 0xffffffff8098121d at netmap_ioctl+0x7ad
>>>>>> #7 0xffffffff8098682f at freebsd_netmap_ioctl+0x5f
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> Vincenzo Maffione
>>>>> _______________________________________________
>>>>> freebsd-net at freebsd.org mailing list
>>>>> https://lists.freebsd.org/mailman/listinfo/freebsd-net
>>>>> To unsubscribe, send any mail to "freebsd-net-unsubscribe at freebsd.org"
>>>
>>>
>>>
>>> --
>>> Vincenzo Maffione
>>> _______________________________________________
>>> freebsd-net at freebsd.org mailing list
>>> https://lists.freebsd.org/mailman/listinfo/freebsd-net
>>> To unsubscribe, send any mail to "freebsd-net-unsubscribe at freebsd.org"
>
>
>
> --
> Vincenzo Maffione



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