From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1AD30C43441 for ; Mon, 26 Nov 2018 19:35:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D105D20855 for ; Mon, 26 Nov 2018 19:35:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="AX1JRh3h" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D105D20855 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726914AbeK0GaO (ORCPT ); Tue, 27 Nov 2018 01:30:14 -0500 Received: from mail.kernel.org ([198.145.29.99]:51472 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726294AbeK0GaO (ORCPT ); Tue, 27 Nov 2018 01:30:14 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 555B9205C9; Mon, 26 Nov 2018 19:35:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1543260905; bh=igG4ljGHCeXB0Sb4i3toRXbFFJ4AVTRXUDJ6Jjt8esQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=AX1JRh3hANqNu+XKGfFHaXe5l/ZxmhqgKCHX6rQ4ZJj8p3sSSfSdHI6Cq491MMjRp m82HckI2I5VMUl67RgZmo3cJbtQJS7IOlXdWhCOaqVuy5FgZfv+wb17pmqpAF92WuM Hlqn9KhyWQMowhZcA/K+L61IvkpX3Y8KQpMmZY5w= Date: Mon, 26 Nov 2018 20:35:03 +0100 From: Greg KH To: kys@microsoft.com Cc: linux-kernel@vger.kernel.org, devel@linuxdriverproject.org, olaf@aepfle.de, apw@canonical.com, jasowang@redhat.com, sthemmin@microsoft.com, Michael.H.Kelley@microsoft.com, vkuznets@redhat.com, Haiyang Zhang , stable@vger.kernel.org Subject: Re: [PATCH 2/2] Drivers: hv: vmbus: offload the handling of channels to two workqueues Message-ID: <20181126193503.GA25649@kroah.com> References: <20181126022821.11269-1-kys@linuxonhyperv.com> <20181126022958.11320-1-kys@linuxonhyperv.com> <20181126022958.11320-2-kys@linuxonhyperv.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181126022958.11320-2-kys@linuxonhyperv.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 26, 2018 at 02:29:57AM +0000, kys@linuxonhyperv.com wrote: > From: Dexuan Cui > > vmbus_process_offer() mustn't call channel->sc_creation_callback() > directly for sub-channels, because sc_creation_callback() -> > vmbus_open() may never get the host's response to the > OPEN_CHANNEL message (the host may rescind a channel at any time, > e.g. in the case of hot removing a NIC), and vmbus_onoffer_rescind() > may not wake up the vmbus_open() as it's blocked due to a non-zero > vmbus_connection.offer_in_progress, and finally we have a deadlock. > > The above is also true for primary channels, if the related device > drivers use sync probing mode by default. > > And, usually the handling of primary channels and sub-channels can > depend on each other, so we should offload them to different > workqueues to avoid possible deadlock, e.g. in sync-probing mode, > NIC1's netvsc_subchan_work() can race with NIC2's netvsc_probe() -> > rtnl_lock(), and causes deadlock: the former gets the rtnl_lock > and waits for all the sub-channels to appear, but the latter > can't get the rtnl_lock and this blocks the handling of sub-channels. > > The patch can fix the multiple-NIC deadlock described above for > v3.x kernels (e.g. RHEL 7.x) which don't support async-probing > of devices, and v4.4, v4.9, v4.14 and v4.18 which support async-probing > but don't enable async-probing for Hyper-V drivers (yet). > > The patch can also fix the hang issue in sub-channel's handling described > above for all versions of kernels, including v4.19 and v4.20-rc3. > > So the patch should be applied to all the existing kernels. > > Fixes: 8195b1396ec8 ("hv_netvsc: fix deadlock on hotplug") > Cc: stable@vger.kernel.org > Cc: Stephen Hemminger > Cc: K. Y. Srinivasan > Cc: Haiyang Zhang > Signed-off-by: Dexuan Cui > Signed-off-by: K. Y. Srinivasan > --- > drivers/hv/channel_mgmt.c | 188 +++++++++++++++++++++++++------------- > drivers/hv/connection.c | 24 ++++- > drivers/hv/hyperv_vmbus.h | 7 ++ > include/linux/hyperv.h | 7 ++ > 4 files changed, 161 insertions(+), 65 deletions(-) As Sasha pointed out, this patch does not even apply :(