From owner-freebsd-net@freebsd.org Wed Dec 28 18:25:25 2016 Return-Path: Delivered-To: freebsd-net@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 2D0F2C94125 for ; Wed, 28 Dec 2016 18:25:25 +0000 (UTC) (envelope-from v.maffione@gmail.com) Received: from mail-oi0-x244.google.com (mail-oi0-x244.google.com [IPv6:2607:f8b0:4003:c06::244]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id EEBBC15B1; Wed, 28 Dec 2016 18:25:24 +0000 (UTC) (envelope-from v.maffione@gmail.com) Received: by mail-oi0-x244.google.com with SMTP id 3so23397074oih.1; Wed, 28 Dec 2016 10:25:24 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=i3ZIsUUBqcbzOgP/N6CDlWkY3z9wMfJnAgS70+1iXtY=; b=Za3glGU3Tio9HOCfSD48WZV4Y9XDq9VdkdIRaLfCJ9XjbKRPqTxDoX+jt1eguMmG8m 8QXKJFRKzD9FaXKtjzmjomwpgnVHXpwhBmqP/qOYFlObSqKvHUZj3UASv83B2A52iYom n2DhT7+oz7WBCKKnlODDI1aiSNR6cMmOMwLc1ANxD2iMzlebhaAL0Mfgj+Ta8Ier9kTn wMOgpI8U2a4wAEeaZ574WgKtj0PY+OC72UUVXgE/d16Y0CXzuSdNkQly5pOEnx7Yh7Aa T1WTaj0bwmMfVRfUbODOAaj97o66b02cd/kuHSPMJK9PvQqABROgxZ+tqcUYu5vhpQqN PNAQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=i3ZIsUUBqcbzOgP/N6CDlWkY3z9wMfJnAgS70+1iXtY=; b=GPoqdzmb3Yf27RRGwu9/mdwyvvaugvrXMTiyi0e9DgkC51jDebRvzGP/z2OKJbxmJB b5SoEJ/igjsoGKMzYciNarZaC6Q64SqAhCveGn2ecz/Uyvq2T4ZO5wTBC1Amv9wCwIT1 CKpljNNNccW/CQFG3U1l00owNZD7fQEe83186MIla1mDut+bS5nAotpGadj4e0zFrpXD 0n95xQLCjlJGlfiIXFIQzOT/6Dd8W0wt/2jXvjKfWzm7xugy14R0OFHTmGGnIGhQJHst YDaHUtqtvAOf4Lk1juIj4JxcVLBaBsQACF0WBpafkUoCfo1kld6hN+qKsS/9BAYL/9hv Q/NA== X-Gm-Message-State: AIkVDXKGaeFOfE91EEhvMEa0Dri+HYfBMpWAEojn83AnW7+0oQSztaT+qCxPonfgphlIrTkuxjnK60hKm+jxlg== X-Received: by 10.157.12.172 with SMTP id b41mr20506757otb.105.1482949522882; Wed, 28 Dec 2016 10:25:22 -0800 (PST) MIME-Version: 1.0 Received: by 10.157.45.200 with HTTP; Wed, 28 Dec 2016 10:25:22 -0800 (PST) In-Reply-To: <2698793.0b4KyHrqck@ralph.baldwin.cx> References: <20161217222812.GA4979@ox> <2698793.0b4KyHrqck@ralph.baldwin.cx> From: Vincenzo Maffione Date: Wed, 28 Dec 2016 19:25:22 +0100 Message-ID: Subject: Re: cxgbe's native netmap support broken since r307394 To: John Baldwin Cc: "freebsd-net@freebsd.org" , Luigi Rizzo , Adrian Chadd , Giuseppe Lettieri , Luigi Rizzo , Navdeep Parhar Content-Type: text/plain; charset=UTF-8 X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 28 Dec 2016 18:25:25 -0000 Hi, The "worker_lock" is taken by nm_os_kthread_wakeup_worker(), which in turn is called by nm_pt_host_notify(). The latter function is a callback that may be called by a driver interrupt service routine; more precisely this happens when the driver calls netmap_tx_irq() or netmap_rx_irq(). As far as I know in FreeBSD it is not possible to lock a MTX_DEF mtx inside an ISR. Am I wrong on this? Cheers, Vincenzo 2016-12-28 19:06 GMT+01:00 John Baldwin : > Why are you using MTX_SPIN? Changing the lock type to MTX_DEF would seem to > be a smaller patch and probably more correct for FreeBSD. > > On Thursday, December 22, 2016 05:29:41 PM Luigi Rizzo wrote: >> sure go ahead and thank you! >> >> On Thu, Dec 22, 2016 at 5:15 PM, Adrian Chadd wrote: >> > ok, does anyone mind if I commit it as-is? >> > >> > >> > -a >> > >> > >> > On 21 December 2016 at 13:37, Vincenzo Maffione 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 : >> >>> On Wed, Dec 21, 2016 at 11:15 AM, Vincenzo Maffione >> >>> 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 : >> >>>>> hi, >> >>>>> >> >>>>> What's the commit? We should get it into -HEAD asap. >> >>>>> >> >>>>> >> >>>>> -adrian >> >>>>> >> >>>>> >> >>>>> On 20 December 2016 at 01:25, Vincenzo Maffione 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 : >> >>>>>>> IFNET_RLOCK will work, thanks. >> >>>>>>> >> >>>>>>> Navdeep >> >>>>>>> >> >>>>>>> On Mon, Dec 19, 2016 at 3:21 AM, Vincenzo Maffione 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 : >> >>>>>>>>> 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 >> >> >> >> > > > -- > John Baldwin -- Vincenzo Maffione