From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933333AbcFHQGG (ORCPT ); Wed, 8 Jun 2016 12:06:06 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54709 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933271AbcFHQGB (ORCPT ); Wed, 8 Jun 2016 12:06:01 -0400 From: Vitaly Kuznetsov To: netdev@vger.kernel.org Cc: devel@linuxdriverproject.org, linux-kernel@vger.kernel.org, "K. Y. Srinivasan" , Haiyang Zhang Subject: Re: [PATCH RFC net-next] netvsc: get rid of completion timeouts References: <1465395546-28272-1-git-send-email-vkuznets@redhat.com> Date: Wed, 08 Jun 2016 18:05:57 +0200 In-Reply-To: <1465395546-28272-1-git-send-email-vkuznets@redhat.com> (Vitaly Kuznetsov's message of "Wed, 8 Jun 2016 16:19:06 +0200") Message-ID: <87inxjacnu.fsf@vitty.brq.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Wed, 08 Jun 2016 16:06:00 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Vitaly Kuznetsov writes: > I'm hitting 5 second timeout in rndis_filter_set_rss_param() while setting > RSS parameters for the device. When this happens we end up returning > -ETIMEDOUT from the function and rndis_filter_device_add() falls back to > setting > > net_device->max_chn = 1; > net_device->num_chn = 1; > net_device->num_sc_offered = 0; > > but after a moment the rndis request succeeds and subchannels start to > appear. netvsc_sc_open() does unconditional nvscdev->num_sc_offered-- and > it becomes U32_MAX-1. Consequent rndis_filter_device_remove() will hang > while waiting for all U32_MAX-1 subchannels to appear and this is not > going to happen. > > The immediate issue could be solved by adding num_sc_offered > 0 check to > netvsc_sc_open() but we're getting out of sync with the host and it's not > easy to adjust things later, e.g. in this particular case we'll be creating > queues without a user request for it and races are expected. Same applies > to other parts of the driver which have the same completion timeout. > > Following the trend in drivers/hv/* code I suggest we remove all these > timeouts completely. As a guest we can always trust the host we're running > on and if the host screws things up there is no easy way to recover anyway. > > Signed-off-by: Vitaly Kuznetsov Kbuild test robot reports an unused variable after the patch, I'll fix this and resend together with a related fix so please don't apply this RFC to net-next atm. [skip] -- Vitaly