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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 80021C433EF for ; Tue, 5 Jul 2022 11:22:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231702AbiGELWs (ORCPT ); Tue, 5 Jul 2022 07:22:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37140 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231390AbiGELWm (ORCPT ); Tue, 5 Jul 2022 07:22:42 -0400 Received: from out30-57.freemail.mail.aliyun.com (out30-57.freemail.mail.aliyun.com [115.124.30.57]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0D38415FC8; Tue, 5 Jul 2022 04:22:40 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R131e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046051;MF=mqaio@linux.alibaba.com;NM=1;PH=DS;RN=9;SR=0;TI=SMTPD_---0VIS5kQb_1657020156; Received: from localhost(mailfrom:mqaio@linux.alibaba.com fp:SMTPD_---0VIS5kQb_1657020156) by smtp.aliyun-inc.com; Tue, 05 Jul 2022 19:22:37 +0800 From: Qiao Ma To: davem@davemloft.net, edumazet@google.com, pabeni@redhat.com, kuba@kernel.org, gustavoars@kernel.org, cai.huoqing@linux.dev Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH net-next v4 2/2] net: hinic: avoid kernel hung in hinic_get_stats64() Date: Tue, 5 Jul 2022 19:22:23 +0800 Message-Id: <6dbe7f2271a2427a8ac4deb57205ea98d1b48c07.1657019476.git.mqaio@linux.alibaba.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <223457a56893fb39648ab51b9c4ed4369b415f72.1657019476.git.mqaio@linux.alibaba.com> References: <223457a56893fb39648ab51b9c4ed4369b415f72.1657019476.git.mqaio@linux.alibaba.com> In-Reply-To: References: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When using hinic device as a bond slave device, and reading device stats of master bond device, the kernel may hung. The kernel panic calltrace as follows: Kernel panic - not syncing: softlockup: hung tasks Call trace: native_queued_spin_lock_slowpath+0x1ec/0x31c dev_get_stats+0x60/0xcc dev_seq_printf_stats+0x40/0x120 dev_seq_show+0x1c/0x40 seq_read_iter+0x3c8/0x4dc seq_read+0xe0/0x130 proc_reg_read+0xa8/0xe0 vfs_read+0xb0/0x1d4 ksys_read+0x70/0xfc __arm64_sys_read+0x20/0x30 el0_svc_common+0x88/0x234 do_el0_svc+0x2c/0x90 el0_svc+0x1c/0x30 el0_sync_handler+0xa8/0xb0 el0_sync+0x148/0x180 And the calltrace of task that actually caused kernel hungs as follows: __switch_to+124 __schedule+548 schedule+72 schedule_timeout+348 __down_common+188 __down+24 down+104 hinic_get_stats64+44 [hinic] dev_get_stats+92 bond_get_stats+172 [bonding] dev_get_stats+92 dev_seq_printf_stats+60 dev_seq_show+24 seq_read_iter+964 seq_read+220 proc_reg_read+164 vfs_read+172 ksys_read+108 __arm64_sys_read+28 el0_svc_common+132 do_el0_svc+40 el0_svc+24 el0_sync_handler+164 el0_sync+324 When getting device stats from bond, kernel will call bond_get_stats(). It first holds the spinlock bond->stats_lock, and then call hinic_get_stats64() to collect hinic device's stats. However, hinic_get_stats64() calls `down(&nic_dev->mgmt_lock)` to protect its critical section, which may schedule current task out. And if system is under high pressure, the task cannot be woken up immediately, which eventually triggers kernel hung panic. Since previous patch has replaced hinic_dev.tx_stats/rx_stats with local variable in hinic_get_stats64(), there is nothing need to be protected by lock, so just removing down()/up() is ok. Fixes: edd384f682cc ("net-next/hinic: Add ethtool and stats") Signed-off-by: Qiao Ma --- drivers/net/ethernet/huawei/hinic/hinic_main.c | 4 ---- 1 file changed, 4 deletions(-) diff --git a/drivers/net/ethernet/huawei/hinic/hinic_main.c b/drivers/net/ethernet/huawei/hinic/hinic_main.c index 89dc52510fdc..c23ee2ddbce3 100644 --- a/drivers/net/ethernet/huawei/hinic/hinic_main.c +++ b/drivers/net/ethernet/huawei/hinic/hinic_main.c @@ -842,13 +842,9 @@ static void hinic_get_stats64(struct net_device *netdev, struct hinic_rxq_stats nic_rx_stats = {}; struct hinic_txq_stats nic_tx_stats = {}; - down(&nic_dev->mgmt_lock); - if (nic_dev->flags & HINIC_INTF_UP) gather_nic_stats(nic_dev, &nic_rx_stats, &nic_tx_stats); - up(&nic_dev->mgmt_lock); - stats->rx_bytes = nic_rx_stats.bytes; stats->rx_packets = nic_rx_stats.pkts; stats->rx_errors = nic_rx_stats.errors; -- 1.8.3.1