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=-6.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 AE128C07E85 for ; Tue, 11 Dec 2018 15:53:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5F42F2146E for ; Tue, 11 Dec 2018 15:53:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1544543602; bh=exS4iVnafaeI9QA46q2R0jMfgG4OsN6lSduq+5AoD3s=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=B3QPR5qY3rBYNXIwIXU4yfJbrtJO1rCEtILvXO9cJG+6erQdRU4t96Om8E4A+a2dF 5a86USIBIWatjTcsMyrhoPxCawrYhlkasMONLdVLdS1DPStMjfMIQP+Aq1+zhAk2yr pHeqfLK7Usr4njYws+yhIle1uSFsIXHIUnlolWTE= DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5F42F2146E 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 S1729922AbeLKPxV (ORCPT ); Tue, 11 Dec 2018 10:53:21 -0500 Received: from mail.kernel.org ([198.145.29.99]:41990 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729904AbeLKPxS (ORCPT ); Tue, 11 Dec 2018 10:53:18 -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 54D532146D; Tue, 11 Dec 2018 15:53:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1544543596; bh=exS4iVnafaeI9QA46q2R0jMfgG4OsN6lSduq+5AoD3s=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=bKvXj2IAl55oMAu29+MeztGumATLpoxwU5ajpFLOythZbomvgOm4DJRrVOTOZpMpb pWCbbbowgCuD3zzpcmXkVHLnc8xrNB0ednsiOFej/jf73Hpy7F/6cIKt8QWN6cs8W3 VLkiSaSElnUFKAQXMyuMllf6mQ69oRhnC3YQ2wKE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Stephen Hemminger , "K. Y. Srinivasan" , Haiyang Zhang , Dexuan Cui Subject: [PATCH 4.14 58/67] Drivers: hv: vmbus: Offload the handling of channels to two workqueues Date: Tue, 11 Dec 2018 16:41:58 +0100 Message-Id: <20181211151633.318780100@linuxfoundation.org> X-Mailer: git-send-email 2.20.0 In-Reply-To: <20181211151630.378216233@linuxfoundation.org> References: <20181211151630.378216233@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Dexuan Cui commit 37c2578c0c40e286bc0d30bdc05290b2058cf66e upstream. 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-rc4. So actually the patch should be applied to all the existing kernels, not only the kernels that have 8195b1396ec8. 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 Signed-off-by: Greg Kroah-Hartman --- drivers/hv/channel_mgmt.c | 185 +++++++++++++++++++++++++++++++--------------- drivers/hv/connection.c | 24 +++++ drivers/hv/hyperv_vmbus.h | 7 + include/linux/hyperv.h | 7 + 4 files changed, 160 insertions(+), 63 deletions(-) --- a/drivers/hv/channel_mgmt.c +++ b/drivers/hv/channel_mgmt.c @@ -444,61 +444,16 @@ void vmbus_free_channels(void) } } -/* - * vmbus_process_offer - Process the offer by creating a channel/device - * associated with this offer - */ -static void vmbus_process_offer(struct vmbus_channel *newchannel) +/* Note: the function can run concurrently for primary/sub channels. */ +static void vmbus_add_channel_work(struct work_struct *work) { - struct vmbus_channel *channel; - bool fnew = true; + struct vmbus_channel *newchannel = + container_of(work, struct vmbus_channel, add_channel_work); + struct vmbus_channel *primary_channel = newchannel->primary_channel; unsigned long flags; u16 dev_type; int ret; - /* Make sure this is a new offer */ - mutex_lock(&vmbus_connection.channel_mutex); - - /* - * Now that we have acquired the channel_mutex, - * we can release the potentially racing rescind thread. - */ - atomic_dec(&vmbus_connection.offer_in_progress); - - list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) { - if (!uuid_le_cmp(channel->offermsg.offer.if_type, - newchannel->offermsg.offer.if_type) && - !uuid_le_cmp(channel->offermsg.offer.if_instance, - newchannel->offermsg.offer.if_instance)) { - fnew = false; - break; - } - } - - if (fnew) - list_add_tail(&newchannel->listentry, - &vmbus_connection.chn_list); - - mutex_unlock(&vmbus_connection.channel_mutex); - - if (!fnew) { - /* - * Check to see if this is a sub-channel. - */ - if (newchannel->offermsg.offer.sub_channel_index != 0) { - /* - * Process the sub-channel. - */ - newchannel->primary_channel = channel; - spin_lock_irqsave(&channel->lock, flags); - list_add_tail(&newchannel->sc_list, &channel->sc_list); - channel->num_sc++; - spin_unlock_irqrestore(&channel->lock, flags); - } else { - goto err_free_chan; - } - } - dev_type = hv_get_dev_type(newchannel); init_vp_index(newchannel, dev_type); @@ -516,21 +471,22 @@ static void vmbus_process_offer(struct v /* * This state is used to indicate a successful open * so that when we do close the channel normally, we - * can cleanup properly + * can cleanup properly. */ newchannel->state = CHANNEL_OPEN_STATE; - if (!fnew) { - if (channel->sc_creation_callback != NULL) - channel->sc_creation_callback(newchannel); + if (primary_channel != NULL) { + /* newchannel is a sub-channel. */ + + if (primary_channel->sc_creation_callback != NULL) + primary_channel->sc_creation_callback(newchannel); + newchannel->probe_done = true; return; } /* - * Start the process of binding this offer to the driver - * We need to set the DeviceObject field before calling - * vmbus_child_dev_add() + * Start the process of binding the primary channel to the driver */ newchannel->device_obj = vmbus_device_create( &newchannel->offermsg.offer.if_type, @@ -559,13 +515,28 @@ static void vmbus_process_offer(struct v err_deq_chan: mutex_lock(&vmbus_connection.channel_mutex); - list_del(&newchannel->listentry); + + /* + * We need to set the flag, otherwise + * vmbus_onoffer_rescind() can be blocked. + */ + newchannel->probe_done = true; + + if (primary_channel == NULL) { + list_del(&newchannel->listentry); + } else { + spin_lock_irqsave(&primary_channel->lock, flags); + list_del(&newchannel->sc_list); + spin_unlock_irqrestore(&primary_channel->lock, flags); + } + mutex_unlock(&vmbus_connection.channel_mutex); if (newchannel->target_cpu != get_cpu()) { put_cpu(); smp_call_function_single(newchannel->target_cpu, - percpu_channel_deq, newchannel, true); + percpu_channel_deq, + newchannel, true); } else { percpu_channel_deq(newchannel); put_cpu(); @@ -573,14 +544,104 @@ err_deq_chan: vmbus_release_relid(newchannel->offermsg.child_relid); -err_free_chan: free_channel(newchannel); } /* + * vmbus_process_offer - Process the offer by creating a channel/device + * associated with this offer + */ +static void vmbus_process_offer(struct vmbus_channel *newchannel) +{ + struct vmbus_channel *channel; + struct workqueue_struct *wq; + unsigned long flags; + bool fnew = true; + + mutex_lock(&vmbus_connection.channel_mutex); + + /* + * Now that we have acquired the channel_mutex, + * we can release the potentially racing rescind thread. + */ + atomic_dec(&vmbus_connection.offer_in_progress); + + list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) { + if (!uuid_le_cmp(channel->offermsg.offer.if_type, + newchannel->offermsg.offer.if_type) && + !uuid_le_cmp(channel->offermsg.offer.if_instance, + newchannel->offermsg.offer.if_instance)) { + fnew = false; + break; + } + } + + if (fnew) + list_add_tail(&newchannel->listentry, + &vmbus_connection.chn_list); + else { + /* + * Check to see if this is a valid sub-channel. + */ + if (newchannel->offermsg.offer.sub_channel_index == 0) { + mutex_unlock(&vmbus_connection.channel_mutex); + /* + * Don't call free_channel(), because newchannel->kobj + * is not initialized yet. + */ + kfree(newchannel); + WARN_ON_ONCE(1); + return; + } + /* + * Process the sub-channel. + */ + newchannel->primary_channel = channel; + spin_lock_irqsave(&channel->lock, flags); + list_add_tail(&newchannel->sc_list, &channel->sc_list); + spin_unlock_irqrestore(&channel->lock, flags); + } + + mutex_unlock(&vmbus_connection.channel_mutex); + + /* + * 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. + */ + INIT_WORK(&newchannel->add_channel_work, vmbus_add_channel_work); + wq = fnew ? vmbus_connection.handle_primary_chan_wq : + vmbus_connection.handle_sub_chan_wq; + queue_work(wq, &newchannel->add_channel_work); +} + +/* * We use this state to statically distribute the channel interrupt load. */ static int next_numa_node_id; +/* + * init_vp_index() accesses global variables like next_numa_node_id, and + * it can run concurrently for primary channels and sub-channels: see + * vmbus_process_offer(), so we need the lock to protect the global + * variables. + */ +static DEFINE_SPINLOCK(bind_channel_to_cpu_lock); /* * Starting with Win8, we can statically distribute the incoming @@ -618,6 +679,8 @@ static void init_vp_index(struct vmbus_c return; } + spin_lock(&bind_channel_to_cpu_lock); + /* * Based on the channel affinity policy, we will assign the NUMA * nodes. @@ -700,6 +763,8 @@ static void init_vp_index(struct vmbus_c channel->target_cpu = cur_cpu; channel->target_vp = hv_cpu_number_to_vp_number(cur_cpu); + spin_unlock(&bind_channel_to_cpu_lock); + free_cpumask_var(available_mask); } --- a/drivers/hv/connection.c +++ b/drivers/hv/connection.c @@ -161,6 +161,20 @@ int vmbus_connect(void) goto cleanup; } + vmbus_connection.handle_primary_chan_wq = + create_workqueue("hv_pri_chan"); + if (!vmbus_connection.handle_primary_chan_wq) { + ret = -ENOMEM; + goto cleanup; + } + + vmbus_connection.handle_sub_chan_wq = + create_workqueue("hv_sub_chan"); + if (!vmbus_connection.handle_sub_chan_wq) { + ret = -ENOMEM; + goto cleanup; + } + INIT_LIST_HEAD(&vmbus_connection.chn_msg_list); spin_lock_init(&vmbus_connection.channelmsg_lock); @@ -251,10 +265,14 @@ void vmbus_disconnect(void) */ vmbus_initiate_unload(false); - if (vmbus_connection.work_queue) { - drain_workqueue(vmbus_connection.work_queue); + if (vmbus_connection.handle_sub_chan_wq) + destroy_workqueue(vmbus_connection.handle_sub_chan_wq); + + if (vmbus_connection.handle_primary_chan_wq) + destroy_workqueue(vmbus_connection.handle_primary_chan_wq); + + if (vmbus_connection.work_queue) destroy_workqueue(vmbus_connection.work_queue); - } if (vmbus_connection.int_page) { free_pages((unsigned long)vmbus_connection.int_page, 0); --- a/drivers/hv/hyperv_vmbus.h +++ b/drivers/hv/hyperv_vmbus.h @@ -327,7 +327,14 @@ struct vmbus_connection { struct list_head chn_list; struct mutex channel_mutex; + /* + * An offer message is handled first on the work_queue, and then + * is further handled on handle_primary_chan_wq or + * handle_sub_chan_wq. + */ struct workqueue_struct *work_queue; + struct workqueue_struct *handle_primary_chan_wq; + struct workqueue_struct *handle_sub_chan_wq; }; --- a/include/linux/hyperv.h +++ b/include/linux/hyperv.h @@ -869,6 +869,13 @@ struct vmbus_channel { bool probe_done; + /* + * We must offload the handling of the primary/sub channels + * from the single-threaded vmbus_connection.work_queue to + * two different workqueue, otherwise we can block + * vmbus_connection.work_queue and hang: see vmbus_process_offer(). + */ + struct work_struct add_channel_work; }; static inline bool is_hvsock_channel(const struct vmbus_channel *c)