Date: Wed, 21 Dec 2016 11:30:56 -0800 From: Luigi Rizzo <rizzo@iet.unipi.it> To: Vincenzo Maffione <v.maffione@gmail.com> Cc: Adrian Chadd <adrian.chadd@gmail.com>, Navdeep Parhar <np@freebsd.org>, "freebsd-net@freebsd.org" <freebsd-net@freebsd.org>, Luigi Rizzo <luigi@freebsd.org>, Giuseppe Lettieri <g.lettieri@iet.unipi.it> Subject: Re: cxgbe's native netmap support broken since r307394 Message-ID: <CA%2BhQ2%2Bjnrk%2Bz0iCcDsk1uk6u-QagrmkvbZMqE5BQZJCnRggpLw@mail.gmail.com> In-Reply-To: <CA%2B_eA9hAjK-i762t=ZCKqzrk5EDeEJM9gf%2BOAmDJqyUGrAYcFg@mail.gmail.com> References: <20161217222812.GA4979@ox> <CA%2B_eA9jxs3FatSLs8fseb%2BJSrqWrYkegDHyKA1q2QH=Q4_LbJQ@mail.gmail.com> <CAPFoGT9VoRWF306gBYgSKd2wi1rx3_2-yLpnxO98GyM0V-0Xog@mail.gmail.com> <CA%2B_eA9iUOZ9JLyx3bbDUZVc=cR6SqxReoOLRHUYQy-BU6Eb-UQ@mail.gmail.com> <CAJ-VmomPW7%2BknAKbaLYjKXfgd=xAH3bYZi_LoxtNf5cuejJeJw@mail.gmail.com> <CA%2B_eA9hAjK-i762t=ZCKqzrk5EDeEJM9gf%2BOAmDJqyUGrAYcFg@mail.gmail.com>
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On Wed, Dec 21, 2016 at 11:15 AM, Vincenzo Maffione <v.maffione@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@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@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@freebsd.org>: >>>> IFNET_RLOCK will work, thanks. >>>> >>>> Navdeep >>>> >>>> On Mon, Dec 19, 2016 at 3:21 AM, Vincenzo Maffione <v.maffione@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@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@freebsd.org mailing list >>>>> https://lists.freebsd.org/mailman/listinfo/freebsd-net >>>>> To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org" >>> >>> >>> >>> -- >>> Vincenzo Maffione >>> _______________________________________________ >>> freebsd-net@freebsd.org mailing list >>> https://lists.freebsd.org/mailman/listinfo/freebsd-net >>> To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org" > > > > -- > Vincenzo Maffione -- -----------------------------------------+------------------------------- Prof. Luigi RIZZO, rizzo@iet.unipi.it . Dip. di Ing. dell'Informazione http://www.iet.unipi.it/~luigi/ . Universita` di Pisa TEL +39-050-2217533 . via Diotisalvi 2 Mobile +39-338-6809875 . 56122 PISA (Italy) -----------------------------------------+-------------------------------
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