From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753832AbcKUKXJ (ORCPT ); Mon, 21 Nov 2016 05:23:09 -0500 Received: from mout.kundenserver.de ([212.227.126.187]:58989 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751264AbcKUKXG (ORCPT ); Mon, 21 Nov 2016 05:23:06 -0500 From: Arnd Bergmann To: Sagi Grimberg Cc: Binoy Jayan , Doug Ledford , Sean Hefty , Hal Rosenstock , Leon Romanovsky , Sagi Grimberg , Bart Van Assche , Nicholas Bellinger , Jenny Derzhavetz , Ira Weiny , Steve Wise , Mark Bloch , Tatyana E Nikolova , Matan Barak , Lijun Ou , "Wei Hu(Xavier)" , Faisal Latif , Mustafa Ismail , Mark Brown , linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org, target-devel@vger.kernel.org Subject: Re: [PATCH v5 5/9] IB/isert: Replace semaphore sem with completion Date: Mon, 21 Nov 2016 11:22:12 +0100 Message-ID: <2625189.HB0S3sfnY7@wuerfel> User-Agent: KMail/5.1.3 (Linux/4.4.0-34-generic; KDE/5.18.0; x86_64; ; ) In-Reply-To: References: <1479708496-9828-1-git-send-email-binoy.jayan@linaro.org> <1479708496-9828-6-git-send-email-binoy.jayan@linaro.org> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Provags-ID: V03:K0:DMvsf+G3FBCH4NJM13EnS5tnSjPm5PwIumB3shWi9gitX9KhM41 GBShy/KHcYyuXFehWKQ5bIRePtWx2N5AXWBWOpVErnnL4xxyrApg//Jd8S5sthTi6qrpChV r3NkiEpUZfVOTbE4JxRaR9kDEMjKtbkhKXDHqxub0TQPUBluz6nr3AUyCnoleyUHtgreO/e ejm5LAdHUEk7HXzJmyrHA== X-UI-Out-Filterresults: notjunk:1;V01:K0:ZNWJT2iaSng=:dsHwhJRuoi7C6HY5UvKokr Kudp+PLw/H5e++E68PkRWqgBgh53iDN7eMYxPvP6t7Ua3hDvF8dD5By6wPOX32/7JFheSvnek SpLSQUSDq2gDUMtE0E+hrRUslgzXtkMHMm7XirtsD9wOiquts1oAlUBcrH/Ga9lb8zb7qecRX NE7XcYYA15vPk6XZIkpGx9lqMUHmi+5g/ALCsqFm20IT/Clwj87BdhwMqjJdCbH011C+gEClT CGdLTZJYqzx3NZcdAlUay4S4q06tWQZC56YW0tcJSxgkVgMCWgk8OZuxd4w373pgUbiSiA1Fx gHH/xjYj4omYwq45Ziad7upOt8DWo4L9H56IGIHrUX9nk9T6ObQ89655fLkX6OMlm4N4o6nA6 CJzgmuUGX1asVSMVmGUoHOXCELmpGa7K54U8MZVcFgduBklYsJ+zWAq2CXu2BMGWvpOinzTlj DG/lsIzXCc7tPu2rDGP25a2NbPQ2CDLhQyE2LvMqxIs4y+xwIvZyafZIjKGzpkf5Uhg9Ypbik MVDZ3R3Lb4zJNJ37WZpd0JHMk4WUpayTR1buLgUrfPilv5aRF9/R4+VewbYYJTWoIdtQhazL4 if7Avkb8CTwXAL2dNBEg3kYjuM+2hsUYUaPjWTyCyfL9X9NDBIdDAFatEgxMmvjHt0QPDQZyE 8TP50DvWDaoVXooNbkutv2LRtiGJL92GffrvQkYMcBIzxJCAi2qtEdz0vC6CzFc/Rkj82ZPco +LK43UG250c4O3V/ Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Monday, November 21, 2016 9:36:22 AM CET Sagi Grimberg wrote: > > diff --git a/drivers/infiniband/ulp/isert/ib_isert.c b/drivers/infiniband/ulp/isert/ib_isert.c > > index 6dd43f6..de80f56 100644 > > --- a/drivers/infiniband/ulp/isert/ib_isert.c > > +++ b/drivers/infiniband/ulp/isert/ib_isert.c > > @@ -619,7 +619,7 @@ > > mutex_unlock(&isert_np->mutex); > > > > isert_info("np %p: Allow accept_np to continue\n", isert_np); > > - up(&isert_np->sem); > > + complete(&isert_np->comp); > > } > > > > static void > > @@ -2311,7 +2311,7 @@ struct rdma_cm_id * > > isert_err("Unable to allocate struct isert_np\n"); > > return -ENOMEM; > > } > > - sema_init(&isert_np->sem, 0); > > + init_completion(&isert_np->comp); > > This is still racy, a connect event can complete just before we > init the completion and *will* get lost... > > This code started off with a waitqueue which exposes the same > problem, see: > 531b7bf4bd79 Target/iser: Fix iscsit_accept_np and rdma_cm racy flow > > So, still NAK from me... I don't see what you mean here. The code using a waitqueue had no counter but the completion does. I had suggested that Binoy add a comment into the code about this, as it is a rarely used property of completions, but it does seem entirely valid to me. Arnd