From mboxrd@z Thu Jan 1 00:00:00 1970 From: Leon Romanovsky Subject: Re: [PATCH rdma-next] Revert "IB/core: Add flow control to the portmapper netlink calls" Date: Mon, 5 Jun 2017 09:03:18 +0300 Message-ID: <20170605060318.GH6868@mtr-leonro.local> References: <20170530212431.GA21008@ssaleem-MOBL4.amr.corp.intel.com> <20170531040437.GE5406@mtr-leonro.local> <20170531174245.GA16304@ssaleem-MOBL4.amr.corp.intel.com> <1496261429.2608.15.camel@sandisk.com> <20170602162849.GA28660@ssaleem-MOBL4.amr.corp.intel.com> <20170604053635.GD6868@mtr-leonro.local> <20170605022313.GB18172@ctung-MOBL3.amr.corp.intel.com> <20170605040030.GG6868@mtr-leonro.local> <20170605042007.GA19068@ctung-MOBL3.amr.corp.intel.com> <20170605045043.GA17148@ctung-MOBL3.amr.corp.intel.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="GUPx2O/K0ibUojHx" Return-path: Content-Disposition: inline In-Reply-To: <20170605045043.GA17148-TZeIlv3TuzOfrEmaQUPKxl95YUYmaKo1UNDiOz3kqAs@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Chien Tin Tung Cc: Shiraz Saleem , Bart Van Assche , "Latif, Faisal" , "leonro-Nfu5REtnQAJWk0Htik3J/w@public.gmane.org" , "Ismail, Mustafa" , "linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org" , "swise-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org" List-Id: linux-rdma@vger.kernel.org --GUPx2O/K0ibUojHx Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Sun, Jun 04, 2017 at 11:50:43PM -0500, Chien Tin Tung wrote: > You jump around in this thread so much it is hard for a sane person to follow > so I will attempt to summarize what has taken place. > > You try to revert a patch that fixed a real problem in portmapper, claiming: > > 1) Code in question impacts the whole RDMA subsystem. > which is false by my multiple replies on this. > 2) There is a deadlock. > Which is false. I'm still asking for proof. > 3) you want netlink receive to be non-blocking and asynchronous > what does that have to do with the non-existing deadlock? > Asnwer is you can't when there isn't one. > If you want it, create a patch for it instead of creating a > regression with a lazy revert. > > I will continue this discussion if you answer directly to any of those > points. If you choose to dance around the subject and claim falsehood, you > will only damage your own creditibility on the list. I hope you take that > to heart. OK, I got your point. It is worthless discussion. FYI, ibnl_unicast holds global lock for whole NETLINK_RDMA static void ibnl_rcv(struct sk_buff *skb) { mutex_lock(&ibnl_mutex); ibnl_rcv_reply_skb(skb); netlink_rcv_skb(skb, &ibnl_rcv_msg); mutex_unlock(&ibnl_mutex); } I'll wait for a maintainer's decision on the proposed patch. Thanks > > Chien > > On Sun, Jun 04, 2017 at 11:20:07PM -0500, Chien Tin Tung wrote: > > Mon, Jun 05, 2017 at 07:00:30AM +0300, Leon Romanovsky wrote: > > > On Sun, Jun 04, 2017 at 09:23:13PM -0500, Chien Tin Tung wrote: > > > > Sun, Jun 04, 2017 at 08:36:35AM +0300, Leon Romanovsky wrote: > > > > > On Fri, Jun 02, 2017 at 11:28:49AM -0500, Shiraz Saleem wrote: > > > > > > On Wed, May 31, 2017 at 02:10:31PM -0600, Bart Van Assche wrote: > > > > > > > On Wed, 2017-05-31 at 12:42 -0500, Shiraz Saleem wrote: > > > > > > > > > 5. I proposed a solution -> go and fix your user space program. > > > > > > > > > > > > > > > > This is a kernel patch you are trying to revert, you are breaking existing > > > > > > > > kernel functionality. Nothing to do with user space. > > > > > > > > > > > > > > > > Bottom line, come up with a solution that will address both port mapper > > > > > > > > functionality and your issue. > > > > > > > > > > > > > > Hello Shiraz, > > > > > > > > > > > > > > Sorry that this means additional work for you, but I agree with Leon that > > > > > > > user space software should not assume that netlink sockets are a reliable > > > > > > > communication mechanism. > > > > > > > > > > > > Hi Bart - Thank you for your response. > > > > > > > > > > > > The original problem was that ibnl_unicast, which is used to send nl messages from > > > > > > portmapper kernel space to user-space, would occasionally and momentarily fail under stress. > > > > > > We could have retried the call for a certain amount of time, but since netlink_unicast has a > > > > > > nonblock/block parameter, we chose to use the blocking option with a timeout. So we thought we > > > > > > did account for deadlocks with this timeout. > > > > > > > > > > Not really, you just reduced the chances. In very large scale, you will > > > > > have a very large chances of such deadlocks. > > > > > > > > Please stop using the word deadlock until you can prove that the deadlock exists with the timeout > > > > in place. > > > > > > Can you please post the whole list of forbidden words? It will be great to > > > have it accompanied with technical response to my and Bart's claims, and > > > to summarize it, it is very simple: "netlink receive should be > > > non-blocking and asynchronous". > > > > Non-blocking and asynchronous is not deadlock, please get it right. Again, provide proof of > > deadlock, until then refrain from using that word in support of your argument. Which you still > > have not proved there is a problem. > > > > Chien > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-rdma" in > > the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html --GUPx2O/K0ibUojHx Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEkhr/r4Op1/04yqaB5GN7iDZyWKcFAlk09CYACgkQ5GN7iDZy WKfvqQ/7BUL3VsIXIJ/FU4JIPiP9agkSXKnAmilER8smnhbRl3nUNREq4aOLbCpW uC+YApyP2Ojuk8/o0WQayzCkqcCfukMEaQeeT+/LdsStZFqWbgM62ScPtuA3NnLG 9IBK4T1Xh3BKWxd1v2llnN80EI2+7tCcQs4ulUiEcyjvV0f/sX9DWxcqhwK49hBR /+KmB50fXV3UW2ZTDfOufwgvBu+/XDo5dLForCw3zQZ1AH4eFf2/bJJVDmFGhzzH LrLq1TgCdM8swVmFVpCnfFfxQ/bxlfQrJkIhAbGVeOWixC+2Qd4re2DzLKXTNnQM 4SYEDM3eyvXLomFAQdcy2S1ND2YdvkPgF3PIB+wlaVi82NLBcdaDe6Jjm7SnBhv0 Pr/ah/hNwfVjoIiBLJoiij2NHPxZdW6HD16MvyiYW1DdTlgH4VC7EJitdvhzStbe WCSyWFApnd7VHZpBFNvI6dyGgJ0XtP3aDHLifxavbBJLjyVjnj5bfh2fF5XjMlyW FB3p6FOLrzU5W9S3GyMUBm8DJecItIyL9DVtKGP6ubHL7DSgacYlAm5M+8KuhgRu eLz7pPUUaQiVXg3sCETcKSbGvYRrSHSF9jhCdRj8ncteHKyeBcNSz8IbFDujtUQ/ VTO9bnwwV363/+zvloSmvOx+mNoCTTeWIe9/AXkhaFbybwhkh6k= =So2J -----END PGP SIGNATURE----- --GUPx2O/K0ibUojHx-- -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html