Date: Thu, 22 Dec 2016 17:29:41 -0800 From: Luigi Rizzo <rizzo@iet.unipi.it> To: Adrian Chadd <adrian.chadd@gmail.com> Cc: Vincenzo Maffione <v.maffione@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%2BjBJXs2gGQaiJVEkFQx=qiecQ=P637epvtex9XcnXzBEQ@mail.gmail.com> In-Reply-To: <CAJ-VmomTTPfr85E1CqbYZ2dj1R7ZPkTFP03Z-AAd_u=5GjNb4g@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> <CA%2BhQ2%2Bjnrk%2Bz0iCcDsk1uk6u-QagrmkvbZMqE5BQZJCnRggpLw@mail.gmail.com> <CA%2B_eA9jGaUJPX9b=8r8xZ4bmryqbFnNogbb2KEOCRcXNpqBmrg@mail.gmail.com> <CAJ-VmomTTPfr85E1CqbYZ2dj1R7ZPkTFP03Z-AAd_u=5GjNb4g@mail.gmail.com>
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sure go ahead and thank you! On Thu, Dec 22, 2016 at 5:15 PM, Adrian Chadd <adrian.chadd@gmail.com> wrote: > ok, does anyone mind if I commit it as-is? > > > -a > > > On 21 December 2016 at 13:37, Vincenzo Maffione <v.maffione@gmail.com> wrote: >> Hi Luigi, >> I attached a minimal change containing two fixes: >> >> - change IFNET_WLOCK into IFNET_RLOCK, to fix the cxgbe issue related >> to this thread >> - use the proper locking functions for the "worker_lock", unrelated >> but needed to avoid the O.S. to trap because of a mismatch between >> MTX_SPIN and MTX_DEF. >> >> Cheers, >> Vincenzo >> >> 2016-12-21 20:30 GMT+01:00 Luigi Rizzo <rizzo@iet.unipi.it>: >>> 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) >>> -----------------------------------------+------------------------------- >> >> >> >> -- >> 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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