From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bart Van Assche Subject: Re: [rdma-next 01/33] Revert "IB/core: Add flow control to the portmapper netlink calls" Date: Wed, 2 Aug 2017 17:11:33 +0000 Message-ID: <1501693892.2437.6.camel@wdc.com> References: <20170801141023.GM13672@mtr-leonro.local> <20170801141842.GA1808@ctung-MOBL3.amr.corp.intel.com> <20170801151511.GA13376@ctung-MOBL3.amr.corp.intel.com> <20170801195840.GC31205@obsidianresearch.com> <20170802034438.GV13672@mtr-leonro.local> <20170802155856.GA21208@obsidianresearch.com> <20170802162938.GC13672@mtr-leonro.local> <20170802164553.GA31901@obsidianresearch.com> <1501692660.2437.4.camel@wdc.com> <20170802170823.GA32513@obsidianresearch.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <20170802170823.GA32513-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org> Content-Language: en-US Content-ID: <9481A4F3346964459924FE4D35AD0CD3-+cFlbfsKLD6cE4WynfumptQqCkab/8FMAL8bYrjMMd8@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: "jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org" Cc: "linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "cl-vYTEC60ixJUAvxtiuMwx3w@public.gmane.org" , "chien.tin.tung-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org" , "leon-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org" , "dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org" List-Id: linux-rdma@vger.kernel.org On Wed, 2017-08-02 at 11:08 -0600, Jason Gunthorpe wrote: > On Wed, Aug 02, 2017 at 04:51:01PM +0000, Bart Van Assche wrote: > =20 > > Although I do not object against the "RDMA/core: Add wait/retry version > > of ibnl_unicast" patch, I hope that you realize that it is an ugly hack > > instead of a proper fix. Anything that makes user space wait longer tha= n > > the socket timeout, e.g. heavy swapping activity or running the user > > space software under a debugger, will cause delivery of the netlink > > message from kernel to user to fail anyway. >=20 > Yes, I assume the iwpm people are aware of this as well, this is why I > used the phrase 'minimize loss'. >=20 > I'm not sure I'd call it a hack though. There is no proper fix here, > messages from kernel to user space must be delivered and processed for > iwpm to function as designed. Maximizing the chance of delivering > unsolicited messages via blocking netlink_unicast is going to be a > necessary component of any design... >=20 > The big point in all of this discussion is that none of this allows > iwpmd to ignore lost messages and it needs to have a sane well thought > out process for resynchronizing with the kernel. Particularly, the > flow that causes sockets to closed must have some kind of resync. >=20 > But even if all that loss resynchronization works perfectly, it is > still very desirable to avoid triggering it! Hello Jason, Because it is not possible to make the current iwpm netlink code work 100% reliably, my proposal is to add a new and redesigned interface for iwpm communication between user space and kernel and to deprecate the current AP= I. Bart.= -- 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