From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga06.intel.com (mga06.intel.com [134.134.136.31]) by dpdk.org (Postfix) with ESMTP id 383A21B4A6 for ; Thu, 11 Oct 2018 00:51:38 +0200 (CEST) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga104.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 10 Oct 2018 15:51:37 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.54,366,1534834800"; d="scan'208";a="80209910" Received: from lesleyma-mobl.ger.corp.intel.com (HELO [10.252.18.196]) ([10.252.18.196]) by orsmga007.jf.intel.com with ESMTP; 10 Oct 2018 15:51:09 -0700 To: Dan Gora Cc: dev@dpdk.org References: <20180628224513.18391-1-dg@adax.com> <20180629015508.26599-1-dg@adax.com> <20180629015508.26599-3-dg@adax.com> <611163de-bef7-488b-a77b-0e1ff190f1fb@intel.com> <0596f426-0fc5-a222-ea68-4407669f9b22@intel.com> From: Ferruh Yigit Openpgp: preference=signencrypt Autocrypt: addr=ferruh.yigit@intel.com; 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WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Subject: Re: [dpdk-dev] [PATCH v2 02/10] kni: separate releasing netdev from freeing KNI interface X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 10 Oct 2018 22:51:39 -0000 On 10/10/2018 7:18 PM, Dan Gora wrote: > On Wed, Oct 10, 2018 at 2:25 PM Ferruh Yigit wrote: >> >> On 9/4/2018 1:36 AM, Dan Gora wrote: >>> Hi Ferruh, >>> >>> I remembered now the motivation behind separating rte_kni_release() >>> and rte_kni_free(). >>> >>> The problem is that the DPDK thread which calls rte_kni_release() >>> _cannot_ be the same thread which handles callbacks from the KNI >>> driver via rte_kni_handle_request(). This is because the thread which >>> calls rte_kni_release() will be stuck down in >>> ioctl(RTE_KNI_IOCTL_RELEASE) when the kernel calls the >>> RTE_KNI_REQ_CFG_NETWORK_IF callback to the DPDK application. Since >>> that thread cannot call rte_kni_handle_request(), the callback would >>> then just timeout unless some other thread calls >>> rte_kni_handle_request(). >>> >>> So then you are in a bit of a chicken and egg situation. You _have_ >>> to have a separate thread calling rte_kni_handle_request periodically, >>> but that thread also _cannot_ run after rte_kni_release returns >>> (actually it's worse than that because it's actually after the >>> ioctl(RTE_KNI_IOCTL_RELEASE) returns and the fifos are freed). >> >> I see, so we have problem in both end, -userspace side and kernel side. >> >> Agreed that separating release & free may help, but I am not sure about adding a >> new API for KNI. >> >> Very simply, what about prevent kni_net_release() send callback to userspace? > > No, because how is the DPDK application going to know when the user > does 'ip link set down dev '? It's important for the DPDK > application to know when the KNI interface is marked down. I mean kni_net_release() called because of unregister_netdev(), it is possible to set a flag in kni_dev_remove(), before unregister_netdev(), and in kni_net_release() don't call kni_net_process_request() if flag is set. Looks like it can work and only a few lines of code, what do you think? > >> This is already not working and removing it resolves the issues you mentioned. > > Huh? How is it not working? Of course it works. The kni_net_release() called because of unregister_netdev() is not working, as you explained in userspace the thread handles request already terminated, even if not in kernel side response not received and timed off because of lock... > >> Sample application calls rte_eth_dev_stop() after release itself, so behavior >> will be same. > > Huh? in kni sample app, in kni_free_kni() rte_eth_dev_stop() is called after rte_kni_release(). So if you prevent kni_net_release() called because of unregister_netdev() to send callback it won't be problem because of existing rte_eth_dev_stop() > >> But the issues in kernel you mentioned, using `dev` after free_netdev() called >> should be addressed. > > Yes, that's why I fixed them in the patches that I sent. > > d >