Date: Mon, 19 Dec 2016 11:05:40 -0800 From: Navdeep Parhar <np@freebsd.org> To: Vincenzo Maffione <v.maffione@gmail.com> Cc: Luigi Rizzo <luigi@freebsd.org>, "freebsd-net@freebsd.org" <freebsd-net@freebsd.org>, Giuseppe Lettieri <g.lettieri@iet.unipi.it> Subject: Re: cxgbe's native netmap support broken since r307394 Message-ID: <CAPFoGT9VoRWF306gBYgSKd2wi1rx3_2-yLpnxO98GyM0V-0Xog@mail.gmail.com> In-Reply-To: <CA%2B_eA9jxs3FatSLs8fseb%2BJSrqWrYkegDHyKA1q2QH=Q4_LbJQ@mail.gmail.com> References: <20161217222812.GA4979@ox> <CA%2B_eA9jxs3FatSLs8fseb%2BJSrqWrYkegDHyKA1q2QH=Q4_LbJQ@mail.gmail.com>
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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"
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