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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,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 217C8C35242 for ; Sat, 25 Jan 2020 00:52:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F10B12071E for ; Sat, 25 Jan 2020 00:52:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387600AbgAYAwU (ORCPT ); Fri, 24 Jan 2020 19:52:20 -0500 Received: from mga07.intel.com ([134.134.136.100]:29977 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387564AbgAYAwU (ORCPT ); Fri, 24 Jan 2020 19:52:20 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 24 Jan 2020 16:52:18 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,359,1574150400"; d="scan'208";a="294841496" Received: from vcostago-desk1.jf.intel.com ([10.54.70.26]) by fmsmga001.fm.intel.com with ESMTP; 24 Jan 2020 16:52:18 -0800 From: Vinicius Costa Gomes To: netdev@vger.kernel.org Cc: Vinicius Costa Gomes , jhs@mojatatu.com, xiyou.wangcong@gmail.com, jiri@resnulli.us, davem@davemloft.net, vladimir.oltean@nxp.com, po.liu@nxp.com Subject: [PATCH net v1 2/3] taprio: Fix still allowing changing the flags during runtime Date: Fri, 24 Jan 2020 16:53:19 -0800 Message-Id: <20200125005320.3353761-3-vinicius.gomes@intel.com> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200125005320.3353761-1-vinicius.gomes@intel.com> References: <20200125005320.3353761-1-vinicius.gomes@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org The check for 'q->flags' being zero allows that, if the taprio instance was created with no 'flags' specified, for 'flags' to be changed. By design this should not be permitted, as it might require changing the enqueue()/dequeue() functions of taprio, which might already be running, and if the hrtimer is enabled or not. The solution is to not support changing flags in any way during "runtime". As a result of this problem the following RCU stall can be observed: [ 1730.558249] rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: [ 1730.558258] rcu: 6-...0: (190 ticks this GP) idle=922/0/0x1 softirq=25580/25582 fqs=16250 [ 1730.558264] (detected by 2, t=65002 jiffies, g=33017, q=81) [ 1730.558269] Sending NMI from CPU 2 to CPUs 6: [ 1730.559277] NMI backtrace for cpu 6 [ 1730.559277] CPU: 6 PID: 0 Comm: swapper/6 Tainted: G E 5.5.0-rc6+ #35 [ 1730.559278] Hardware name: Gigabyte Technology Co., Ltd. Z390 AORUS ULTRA/Z390 AORUS ULTRA-CF, BIOS F7 03/14/2019 [ 1730.559278] RIP: 0010:__hrtimer_run_queues+0xe2/0x440 [ 1730.559278] Code: 48 8b 43 28 4c 89 ff 48 8b 75 c0 48 89 45 c8 e8 f4 bb 7c 00 0f 1f 44 00 00 65 8b 05 40 31 f0 68 89 c0 48 0f a3 05 3e 5c 25 01 <0f> 82 fc 01 00 00 48 8b 45 c8 48 89 df ff d0 89 45 c8 0f 1f 44 00 [ 1730.559279] RSP: 0018:ffff9970802d8f10 EFLAGS: 00000083 [ 1730.559279] RAX: 0000000000000006 RBX: ffff8b31645bff38 RCX: 0000000000000000 [ 1730.559280] RDX: 0000000000000000 RSI: ffffffff9710f2ec RDI: ffffffff978daf0e [ 1730.559280] RBP: ffff9970802d8f68 R08: 0000000000000000 R09: 0000000000000000 [ 1730.559280] R10: 0000018336d7944e R11: 0000000000000001 R12: ffff8b316e39f9c0 [ 1730.559281] R13: ffff8b316e39f940 R14: ffff8b316e39f998 R15: ffff8b316e39f7c0 [ 1730.559281] FS: 0000000000000000(0000) GS:ffff8b316e380000(0000) knlGS:0000000000000000 [ 1730.559281] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 1730.559281] CR2: 00007f1105303760 CR3: 0000000227210005 CR4: 00000000003606e0 [ 1730.559282] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 1730.559282] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 1730.559282] Call Trace: [ 1730.559282] [ 1730.559283] ? taprio_dequeue_soft+0x2d0/0x2d0 [sch_taprio] [ 1730.559283] hrtimer_interrupt+0x104/0x220 [ 1730.559283] ? irqtime_account_irq+0x34/0xa0 [ 1730.559283] smp_apic_timer_interrupt+0x6d/0x230 [ 1730.559284] apic_timer_interrupt+0xf/0x20 [ 1730.559284] [ 1730.559284] RIP: 0010:cpu_idle_poll+0x35/0x1a0 [ 1730.559285] Code: 88 82 ff 65 44 8b 25 12 7d 73 68 0f 1f 44 00 00 e8 90 c3 89 ff fb 65 48 8b 1c 25 c0 7e 01 00 48 8b 03 a8 08 74 0b eb 1c f3 90 <48> 8b 03 a8 08 75 13 8b 05 be a8 a8 00 85 c0 75 ed e8 75 48 84 ff [ 1730.559285] RSP: 0018:ffff997080137ea8 EFLAGS: 00000202 ORIG_RAX: ffffffffffffff13 [ 1730.559285] RAX: 0000000000000001 RBX: ffff8b316bc3c580 RCX: 0000000000000000 [ 1730.559286] RDX: 0000000000000001 RSI: 000000002819aad9 RDI: ffffffff978da730 [ 1730.559286] RBP: ffff997080137ec0 R08: 0000018324a6d387 R09: 0000000000000000 [ 1730.559286] R10: 0000000000000400 R11: 0000000000000001 R12: 0000000000000006 [ 1730.559286] R13: ffff8b316bc3c580 R14: 0000000000000000 R15: 0000000000000000 [ 1730.559287] ? cpu_idle_poll+0x20/0x1a0 [ 1730.559287] ? cpu_idle_poll+0x20/0x1a0 [ 1730.559287] do_idle+0x4d/0x1f0 [ 1730.559287] ? complete+0x44/0x50 [ 1730.559288] cpu_startup_entry+0x1b/0x20 [ 1730.559288] start_secondary+0x142/0x180 [ 1730.559288] secondary_startup_64+0xb6/0xc0 [ 1776.686313] nvme nvme0: I/O 96 QID 1 timeout, completion polled Fixes: 4cfd5779bd6e ("taprio: Add support for txtime-assist mode") Signed-off-by: Vinicius Costa Gomes --- net/sched/sch_taprio.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c index ad0dadcfcdba..dfbecb9ee2f4 100644 --- a/net/sched/sch_taprio.c +++ b/net/sched/sch_taprio.c @@ -1391,7 +1391,7 @@ static int taprio_change(struct Qdisc *sch, struct nlattr *opt, if (tb[TCA_TAPRIO_ATTR_FLAGS]) { taprio_flags = nla_get_u32(tb[TCA_TAPRIO_ATTR_FLAGS]); - if (q->flags != 0 && q->flags != taprio_flags) { + if (q->flags != taprio_flags) { NL_SET_ERR_MSG_MOD(extack, "Changing 'flags' of a running schedule is not supported"); return -EOPNOTSUPP; } else if (!taprio_flags_valid(taprio_flags)) { -- 2.25.0