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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,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 0C8F9C282DD for ; Sat, 20 Apr 2019 08:24:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DB0D4208C0 for ; Sat, 20 Apr 2019 08:24:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727296AbfDTIX5 (ORCPT ); Sat, 20 Apr 2019 04:23:57 -0400 Received: from szxga05-in.huawei.com ([45.249.212.191]:7207 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725911AbfDTIX5 (ORCPT ); Sat, 20 Apr 2019 04:23:57 -0400 Received: from DGGEMS402-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id 800FDDF35A468244ACFA; Sat, 20 Apr 2019 16:23:52 +0800 (CST) Received: from localhost.localdomain.localdomain (10.175.113.25) by DGGEMS402-HUB.china.huawei.com (10.3.19.202) with Microsoft SMTP Server id 14.3.408.0; Sat, 20 Apr 2019 16:23:44 +0800 From: Xie XiuQi To: , CC: , Subject: [PATCH] sched: fix a potential divide error Date: Sat, 20 Apr 2019 16:34:16 +0800 Message-ID: <20190420083416.170446-1-xiexiuqi@huawei.com> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Content-Type: text/plain; charset=US-ASCII X-Originating-IP: [10.175.113.25] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org We meet a divide error on 3.10.0 kernel, the error message is bellow: [499992.287996] divide error: 0000 [#1] SMP [499992.297796] do nothing after die! [499992.299108] Modules linked in: signo_catch macvlan binfmt_misc ip_set_hash_netport ip_set_hash_ipport vport_vxlan ipt_REJECT xt_statistic xt_physdev xt_nat xt_recent xt_mark xt_comment ... [499992.312751] CPU: 8 PID: 23352 Comm: bash Tainted: G ----V------- 3.10.0+ #1 [499992.314308] Hardware name: OpenStack Foundation OpenStack Nova, BIOS rel-1.9.1-0-gb3ef39f-20170329_185309-build9a64a246a231 04/01/2014 [499992.317411] task: ffff880033fc9700 ti: ffff8807fed60000 task.ti:ffff8807fed60000 [499992.318967] RIP: 0010:[] [] task_numa_fault+0x1c2/0xbb0 [499992.320515] RSP: 0000:ffff8807fed63d38 EFLAGS: 00010246 [499992.322018] RAX: 0000002b7efd0000 RBX: ffff880033fc9700 RCX:0000000000000003 [499992.323563] RDX: 0000000000000000 RSI: 0000000000000400 RDI:ffffffff81a80f60 [499992.325052] RBP: ffff8807fed63db8 R08: ffffffff81a80f68 R09:0000000000000000 [499992.326531] R10: ffff88083ffda000 R11: 0000000000000000 R12:0000000000000424 [499992.327987] R13: 00000000002b7efd R14: 0000000000000000 R15:ffffea001ea42a00 [499992.329420] FS: 00007fa01a3b7740(0000) GS:ffff88103ec00000(0000)knlGS:0000000000000000 [499992.330866] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [499992.332302] CR2: 0000000000ff1fb0 CR3: 00000007ff1d1000 CR4:00000000003407e0 [499992.333763] DR0: 0000000000000000 DR1: 0000000000000000 DR2:0000000000000000 [499992.335187] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7:0000000000000400 [499992.336595] Stack: [499992.337974] 0000000000000000 00000001bc9598a8 ffffea001ea42a00 0000000100000001 [499992.339374] 0000000300000001 0000000000000001 ffffea001ea42a00 ffff8807fed63db8 [499992.340768] 0000000000000000 0000000000000000 00000000bc9598a8 0000000000000001 [499992.342148] Call Trace: [499992.343494] [] do_numa_page+0x162/0x1f0 [499992.344831] [] handle_mm_fault+0x627/0xf50 [499992.346145] [] __do_page_fault+0x166/0x470 [499992.347442] [] trace_do_page_fault+0x43/0x110 [499992.348711] [] do_async_page_fault+0x29/0xe0 [499992.349948] [] async_page_fault+0x28/0x30 [499992.351149] Code: 00 3d 00 04 00 00 44 0f 4e d8 41 81 fb 00 04 00 00 0f 84 67 07 00 00 4c 89 e8 49 83 c6 01 31 d2 48 c1 e0 10 49 83 c4 01 45 31 c9 <49> f7 f6 48 c7 45 a8 00 00 00 00 48 c7 45 b0 00 00 00 00 49 89 [499992.353707] RIP [] task_numa_fault+0x1c2/0xbb0 [499992.354927] RSP [499992.358114] ---[ end trace 4f2465cac18ff65e ]--- [499992.359304] Kernel panic - not syncing: Fatal exception sched_clock_cpu may not be consistent bwtwen cpus. If a task migrate to another cpu, the se.exec_start was set to that cpu's rq_clock_task by update_stats_curr_start(). Which may not be monotonic. update_stats_curr_start <- set_next_entity <- set_curr_task_fair <- sched_move_task So, if now - p->last_task_numa_placement is -1, then (*period + 1) is 0, and divide error was triggerred at the div operation: task_numa_placement: runtime = numa_get_avg_runtime(p, &period); f_weight = div64_u64(runtime << 16, period + 1); // divide error here In this patch, we make sure period is not less than 0 to avoid this divide error. Signed-off-by: Xie XiuQi Cc: stable@vger.kernel.org --- kernel/sched/fair.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 40bd1e27b1b7..f2abb258fc85 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2007,6 +2007,10 @@ static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period) if (p->last_task_numa_placement) { delta = runtime - p->last_sum_exec_runtime; *period = now - p->last_task_numa_placement; + + /* Avoid backward, and prevent potential divide error */ + if ((s64)*period < 0) + *period = 0; } else { delta = p->se.avg.load_sum; *period = LOAD_AVG_MAX; -- 2.20.1