From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933002AbcHIXZC (ORCPT ); Tue, 9 Aug 2016 19:25:02 -0400 Received: from mail-cys01nam02on0070.outbound.protection.outlook.com ([104.47.37.70]:37632 "EHLO NAM02-CY1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932990AbcHIXYy (ORCPT ); Tue, 9 Aug 2016 19:24:54 -0400 Authentication-Results: spf=pass (sender IP is 63.163.107.225) smtp.mailfrom=sandisk.com; gmail.com; dkim=none (message not signed) header.d=none;gmail.com; dmarc=bestguesspass action=none header.from=sandisk.com; X-AuditID: ac160c71-20b1198000000e72-d2-57aa613b7e67 Subject: Re: [PATCH] sched: Avoid that __wait_on_bit_lock() hangs To: Oleg Nesterov References: <20160803181128.GH6879@twins.programming.kicks-ass.net> <11007730-3fa5-139a-8091-655743894ae8@sandisk.com> <20160803213006.GA11712@redhat.com> <17b65ff9-215f-ab74-9f5f-15dbd308d054@sandisk.com> <20160804140938.GB24652@twins.programming.kicks-ass.net> <16207b90-2e6c-fe23-1b4b-3763e5cf0384@sandisk.com> <20160808102213.GA6879@twins.programming.kicks-ass.net> <4091e252-18d9-1795-de63-9fbc678aa6b1@acm.org> <20160808162038.GA25927@redhat.com> <78fafdc1-d4ae-a9a2-169c-1d456b6e6e41@sandisk.com> <20160809171459.GA13840@redhat.com> <3cec7657-caa9-92ca-9f0e-34f073a6ed8c@sandisk.com> CC: Peter Zijlstra , "mingo@kernel.org" , Andrew Morton , "Johannes Weiner" , Neil Brown , Michael Shaver , "linux-kernel@vger.kernel.org" From: Bart Van Assche Message-ID: <09659231-5e0e-2767-d180-4285fb6e12b3@sandisk.com> Date: Tue, 9 Aug 2016 16:10:02 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.2 MIME-Version: 1.0 In-Reply-To: <3cec7657-caa9-92ca-9f0e-34f073a6ed8c@sandisk.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFprMIsWRmVeSWpSXmKPExsWyRoxnka5N4qpwg72HmSzmrF/DZrF6k6/F 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1;BN1PR0201MB0545;20:L6TPtjpuwLPwHPGeljUW0G3AFPKkOy5Y6pmG9yfyMODxansqV51crxLM3vJ5X9BnWYL+W4DyuJTzNg+HhyWIod+B5Wwg+YWLkcOYRJGkIgZD2TnMwmgcEtuqLuIPYzoZMMYKBxwqg8jfh/PSDAnBlf2L+HcGH2MiiBnYczrs4EZ3B8cdwzCKOVloGW+l2XfTh3LJiVNrJMUTUh0Aj/ZyURJM3uKqttbpCyGoCHGnhxep5lLFNnHvZxZkPGxrifYx X-OriginatorOrg: sandisk.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 09 Aug 2016 23:10:06.1650 (UTC) X-MS-Exchange-CrossTenant-Id: fcd9ea9c-ae8c-460c-ab3c-3db42d7ac64d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=fcd9ea9c-ae8c-460c-ab3c-3db42d7ac64d;Ip=[63.163.107.225];Helo=[milsmgep14.sandisk.com] X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: BN1PR0201MB0545 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/09/2016 11:48 AM, Bart Van Assche wrote: > [ 1548.018115] sysrq: SysRq : Show Blocked State > [ 1548.018210] task PC stack pid father > [ 1548.018677] systemd-udevd D ffff8803a9f13be8 0 29908 483 0x00000000 > [ 1548.018792] ffff8803a9f13be8 ffffffff82584bd0 00ffffff8252b1b0 ffff88046f0569c0 > [ 1548.018961] ffff88016c98b140 ffff8800757bc9c0 ffff8803a9f14000 ffff88046f0569c0 > [ 1548.019131] 7fffffffffffffff ffffffff8161fcf0 ffff8803a9f13d50 ffff8803a9f13c00 > [ 1548.019316] Call Trace: > [ 1548.019415] [] schedule+0x37/0x90 > [ 1548.019464] [] schedule_timeout+0x27f/0x470 > [ 1548.019758] [] io_schedule_timeout+0x9f/0x110 > [ 1548.019808] [] bit_wait_io+0x16/0x60 > [ 1548.019856] [] __wait_on_bit+0x56/0x80 > [ 1548.019906] [] wait_on_page_bit_killable+0xbd/0xc0 > [ 1548.020006] [] generic_file_read_iter+0x130/0x770 > [ 1548.020158] [] blkdev_read_iter+0x30/0x40 > [ 1548.020209] [] __vfs_read+0xbb/0x130 > [ 1548.020258] [] vfs_read+0x91/0x130 > [ 1548.020305] [] SyS_read+0x44/0xa0 > [ 1548.020354] [] entry_SYSCALL_64_fastpath+0x18/0xa8 (replying to my own e-mail) The above call stack is probably caused by a missing I/O completion somewhere in the I/O stack (not in ib_srp) and hence can be ignored in the context of the discussion about __wait_on_bit_lock(). BTW, I have made the following local change in abort_exclusive_wait() in the hope that if I can trigger this statement that it will provide more information about why the __wait_on_bit_lock() hang happens: diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c index f0fdd8e..fad852d 100644 --- a/kernel/sched/wait.c +++ b/kernel/sched/wait.c @@ -280,6 +280,8 @@ void abort_exclusive_wait(wait_queue_head_t *q, wait_queue_t *wait, __set_current_state(TASK_RUNNING); spin_lock_irqsave(&q->lock, flags); + WARN_ONCE(!list_empty(&wait->task_list) && waitqueue_active(q), + "mode = %#x\n", mode); if (!list_empty(&wait->task_list)) list_del_init(&wait->task_list); else if (waitqueue_active(q)) Bart.