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=-0.4 required=3.0 tests=FROM_LOCAL_HEX, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 4D1F1C0044C for ; Mon, 29 Oct 2018 16:22:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C59CC20664 for ; Mon, 29 Oct 2018 16:22:06 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C59CC20664 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com 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 S1727825AbeJ3BLV (ORCPT ); Mon, 29 Oct 2018 21:11:21 -0400 Received: from mail-it1-f199.google.com ([209.85.166.199]:44831 "EHLO mail-it1-f199.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727665AbeJ3BLV (ORCPT ); Mon, 29 Oct 2018 21:11:21 -0400 Received: by mail-it1-f199.google.com with SMTP id r188-v6so10005417itb.9 for ; Mon, 29 Oct 2018 09:22:03 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:date:in-reply-to:message-id:subject :from:to; bh=cuaGuamn9kC0W//tg3NHLuDXImAoPx4VT4mzaFfFTV0=; b=kzxCBVEa4lRcBErEcS9kbE/jYq6H+6FHJAjX9ya9Bet2/21j6YpCk47LMYggLxWTzg B7QyFVT1y8q22GGcpOd4WW9lLqHf8oEOH67sPOXvLKd4z2wIXHU79qRG12sHqERNC/4T LId89mrA/XSwNbCECbUdIX1SJFsmv2kcRbYR0KbNa394Y+qsjkmj6Ziha1WiM/reMi7J O7uHF/SRZBDJ34WGuPtzQOb/lCG8Xeq+GDQmP7OfSO4CEGAX6z5gj5Nyyzjea2xizElI prD77hoD7Vnm659N8n5LZZEs2gYA0SFyro+Bvxa0t8xhK5fA1O6TAKEQ333euMISZ7pQ NWgg== X-Gm-Message-State: AGRZ1gLBKnfBMbKsiF51P9KgwVz8VRqYV8miK2R4gmZsYmhS95+IolLQ +P9ugkCF9V9TVOD0N/HdqMt0lWWYMk/e6sDfob4hsOeEpjIn X-Google-Smtp-Source: AJdET5dMARJtnOqnUtOHVvfgpqIJnuR1w+BABfViopsmoo0AEOa3AwDkKjr3hqvjp5ctHfrlY7u5sXbw0U6EMZ2ApXSY2h0iIKx+ MIME-Version: 1.0 X-Received: by 2002:a02:1810:: with SMTP id k16-v6mr3995545jad.21.1540830123143; Mon, 29 Oct 2018 09:22:03 -0700 (PDT) Date: Mon, 29 Oct 2018 09:22:03 -0700 In-Reply-To: <00000000000080601805795ada2e@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <000000000000264267057960782a@google.com> Subject: Re: INFO: task hung in vivid_stop_generating_vid_cap From: syzbot To: hverkuil@xs4all.nl, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, mchehab@kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8"; format=flowed; delsp=yes Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org syzbot has found a reproducer for the following crash on: HEAD commit: 9f51ae62c84a Merge git://git.kernel.org/pub/scm/linux/kern.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=14bfad7b400000 kernel config: https://syzkaller.appspot.com/x/.config?x=62118286bb772a24 dashboard link: https://syzkaller.appspot.com/bug?extid=06283a66a648cd073885 compiler: gcc (GCC) 8.0.1 20180413 (experimental) syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15701a33400000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=154c8e4d400000 IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+06283a66a648cd073885@syzkaller.appspotmail.com INFO: task syz-executor686:5724 blocked for more than 140 seconds. Not tainted 4.19.0+ #309 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor686 D24208 5724 5716 0x00000004 Call Trace: context_switch kernel/sched/core.c:2831 [inline] __schedule+0x8cf/0x21d0 kernel/sched/core.c:3480 schedule+0xfe/0x460 kernel/sched/core.c:3524 schedule_timeout+0x1cc/0x260 kernel/time/timer.c:1780 do_wait_for_common kernel/sched/completion.c:83 [inline] __wait_for_common kernel/sched/completion.c:104 [inline] wait_for_common kernel/sched/completion.c:115 [inline] wait_for_completion+0x427/0x8a0 kernel/sched/completion.c:136 kthread_stop+0x1a9/0x900 kernel/kthread.c:550 vivid_stop_generating_vid_cap+0x2bc/0x93b drivers/media/platform/vivid/vivid-kthread-cap.c:919 vid_cap_stop_streaming+0x8d/0xe0 drivers/media/platform/vivid/vivid-vid-cap.c:256 __vb2_queue_cancel+0x171/0xca0 drivers/media/common/videobuf2/videobuf2-core.c:1659 vb2_core_streamoff+0x60/0x140 drivers/media/common/videobuf2/videobuf2-core.c:1795 __vb2_cleanup_fileio+0x73/0x160 drivers/media/common/videobuf2/videobuf2-core.c:2316 vb2_core_queue_release+0x1e/0x80 drivers/media/common/videobuf2/videobuf2-core.c:2043 vb2_queue_release drivers/media/common/videobuf2/videobuf2-v4l2.c:672 [inline] _vb2_fop_release+0x1d2/0x2b0 drivers/media/common/videobuf2/videobuf2-v4l2.c:843 vb2_fop_release+0x77/0xc0 drivers/media/common/videobuf2/videobuf2-v4l2.c:857 vivid_fop_release+0x18e/0x440 drivers/media/platform/vivid/vivid-core.c:474 v4l2_release+0xfb/0x1a0 drivers/media/v4l2-core/v4l2-dev.c:448 __fput+0x385/0xa30 fs/file_table.c:278 ____fput+0x15/0x20 fs/file_table.c:309 task_work_run+0x1e8/0x2a0 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:188 [inline] exit_to_usermode_loop+0x318/0x380 arch/x86/entry/common.c:166 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline] syscall_return_slowpath arch/x86/entry/common.c:268 [inline] do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x400f00 Code: 00 00 00 00 00 00 00 00 00 00 d6 01 00 00 12 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 03 00 00 12 00 00 00 <00> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 b8 02 00 00 12 00 RSP: 002b:00007ffc53169f28 EFLAGS: 00000246 ORIG_RAX: 0000000000000003 RAX: 0000000000000000 RBX: 0000000000000003 RCX: 0000000000400f00 RDX: 00000000000000d6 RSI: 0000000020000140 RDI: 0000000000000003 RBP: 0000000000000000 R08: 00000000024b1880 R09: 00000000004002e0 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401e10 R13: 0000000000401ea0 R14: 0000000000000000 R15: 0000000000000000 INFO: task syz-executor686:5730 blocked for more than 140 seconds. Not tainted 4.19.0+ #309 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor686 D24208 5730 5721 0x00000004 Call Trace: context_switch kernel/sched/core.c:2831 [inline] __schedule+0x8cf/0x21d0 kernel/sched/core.c:3480 schedule+0xfe/0x460 kernel/sched/core.c:3524 schedule_timeout+0x1cc/0x260 kernel/time/timer.c:1780 do_wait_for_common kernel/sched/completion.c:83 [inline] __wait_for_common kernel/sched/completion.c:104 [inline] wait_for_common kernel/sched/completion.c:115 [inline] wait_for_completion+0x427/0x8a0 kernel/sched/completion.c:136 kthread_stop+0x1a9/0x900 kernel/kthread.c:550 vivid_stop_generating_vid_cap+0x2bc/0x93b drivers/media/platform/vivid/vivid-kthread-cap.c:919 vid_cap_stop_streaming+0x8d/0xe0 drivers/media/platform/vivid/vivid-vid-cap.c:256 __vb2_queue_cancel+0x171/0xca0 drivers/media/common/videobuf2/videobuf2-core.c:1659 vb2_core_streamoff+0x60/0x140 drivers/media/common/videobuf2/videobuf2-core.c:1795 __vb2_cleanup_fileio+0x73/0x160 drivers/media/common/videobuf2/videobuf2-core.c:2316 vb2_core_queue_release+0x1e/0x80 drivers/media/common/videobuf2/videobuf2-core.c:2043 vb2_queue_release drivers/media/common/videobuf2/videobuf2-v4l2.c:672 [inline] _vb2_fop_release+0x1d2/0x2b0 drivers/media/common/videobuf2/videobuf2-v4l2.c:843 vb2_fop_release+0x77/0xc0 drivers/media/common/videobuf2/videobuf2-v4l2.c:857 vivid_fop_release+0x18e/0x440 drivers/media/platform/vivid/vivid-core.c:474 v4l2_release+0xfb/0x1a0 drivers/media/v4l2-core/v4l2-dev.c:448 __fput+0x385/0xa30 fs/file_table.c:278 ____fput+0x15/0x20 fs/file_table.c:309 task_work_run+0x1e8/0x2a0 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:188 [inline] exit_to_usermode_loop+0x318/0x380 arch/x86/entry/common.c:166 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline] syscall_return_slowpath arch/x86/entry/common.c:268 [inline] do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x400f00 Code: 00 00 00 00 00 00 00 00 00 00 d6 01 00 00 12 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 03 00 00 12 00 00 00 <00> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 b8 02 00 00 12 00 RSP: 002b:00007ffc53169f28 EFLAGS: 00000246 ORIG_RAX: 0000000000000003 RAX: 0000000000000000 RBX: 0000000000000003 RCX: 0000000000400f00 RDX: 00000000000000d6 RSI: 0000000020000140 RDI: 0000000000000003 RBP: 0000000000000000 R08: 00000000024b1880 R09: 00000000004002e0 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000003fbb5 R13: 0000000000401ea0 R14: 0000000000000000 R15: 0000000000000000 INFO: task syz-executor686:5734 blocked for more than 140 seconds. Not tainted 4.19.0+ #309 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor686 D21848 5734 5720 0x00000004 Call Trace: context_switch kernel/sched/core.c:2831 [inline] __schedule+0x8cf/0x21d0 kernel/sched/core.c:3480 schedule+0xfe/0x460 kernel/sched/core.c:3524 schedule_timeout+0x1cc/0x260 kernel/time/timer.c:1780 do_wait_for_common kernel/sched/completion.c:83 [inline] __wait_for_common kernel/sched/completion.c:104 [inline] wait_for_common kernel/sched/completion.c:115 [inline] wait_for_completion+0x427/0x8a0 kernel/sched/completion.c:136 kthread_stop+0x1a9/0x900 kernel/kthread.c:550 vivid_stop_generating_vid_cap+0x2bc/0x93b drivers/media/platform/vivid/vivid-kthread-cap.c:919 vid_cap_stop_streaming+0x8d/0xe0 drivers/media/platform/vivid/vivid-vid-cap.c:256 __vb2_queue_cancel+0x171/0xca0 drivers/media/common/videobuf2/videobuf2-core.c:1659 vb2_core_streamoff+0x60/0x140 drivers/media/common/videobuf2/videobuf2-core.c:1795 __vb2_cleanup_fileio+0x73/0x160 drivers/media/common/videobuf2/videobuf2-core.c:2316 vb2_core_queue_release+0x1e/0x80 drivers/media/common/videobuf2/videobuf2-core.c:2043 vb2_queue_release drivers/media/common/videobuf2/videobuf2-v4l2.c:672 [inline] _vb2_fop_release+0x1d2/0x2b0 drivers/media/common/videobuf2/videobuf2-v4l2.c:843 vb2_fop_release+0x77/0xc0 drivers/media/common/videobuf2/videobuf2-v4l2.c:857 vivid_fop_release+0x18e/0x440 drivers/media/platform/vivid/vivid-core.c:474 v4l2_release+0xfb/0x1a0 drivers/media/v4l2-core/v4l2-dev.c:448 __fput+0x385/0xa30 fs/file_table.c:278 ____fput+0x15/0x20 fs/file_table.c:309 task_work_run+0x1e8/0x2a0 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:188 [inline] exit_to_usermode_loop+0x318/0x380 arch/x86/entry/common.c:166 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline] syscall_return_slowpath arch/x86/entry/common.c:268 [inline] do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x400f00 Code: 00 00 00 00 00 00 a8 01 00 00 00 00 00 00 36 01 00 00 b5 00 00 00 01 02 00 00 00 00 00 00 00 00 00 00 6a 01 00 00 00 00 00 00 <00> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 RSP: 002b:00007ffc53169f28 EFLAGS: 00000246 ORIG_RAX: 0000000000000003 RAX: 0000000000000000 RBX: 0000000000000003 RCX: 0000000000400f00 RDX: 00000000000000d6 RSI: 0000000020000140 RDI: 0000000000000003 RBP: 0000000000000000 R08: 00000000024b1880 R09: 00000000004002e0 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000003fbc6 R13: 0000000000401ea0 R14: 0000000000000000 R15: 0000000000000000 INFO: task syz-executor686:5881 blocked for more than 140 seconds. Not tainted 4.19.0+ #309 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor686 D24208 5881 5715 0x00000004 Call Trace: context_switch kernel/sched/core.c:2831 [inline] __schedule+0x8cf/0x21d0 kernel/sched/core.c:3480 schedule+0xfe/0x460 kernel/sched/core.c:3524 schedule_timeout+0x1cc/0x260 kernel/time/timer.c:1780 do_wait_for_common kernel/sched/completion.c:83 [inline] __wait_for_common kernel/sched/completion.c:104 [inline] wait_for_common kernel/sched/completion.c:115 [inline] wait_for_completion+0x427/0x8a0 kernel/sched/completion.c:136 kthread_stop+0x1a9/0x900 kernel/kthread.c:550 vivid_stop_generating_vid_cap+0x2bc/0x93b drivers/media/platform/vivid/vivid-kthread-cap.c:919 vid_cap_stop_streaming+0x8d/0xe0 drivers/media/platform/vivid/vivid-vid-cap.c:256 __vb2_queue_cancel+0x171/0xca0 drivers/media/common/videobuf2/videobuf2-core.c:1659 vb2_core_streamoff+0x60/0x140 drivers/media/common/videobuf2/videobuf2-core.c:1795 __vb2_cleanup_fileio+0x73/0x160 drivers/media/common/videobuf2/videobuf2-core.c:2316 vb2_core_queue_release+0x1e/0x80 drivers/media/common/videobuf2/videobuf2-core.c:2043 vb2_queue_release drivers/media/common/videobuf2/videobuf2-v4l2.c:672 [inline] _vb2_fop_release+0x1d2/0x2b0 drivers/media/common/videobuf2/videobuf2-v4l2.c:843 vb2_fop_release+0x77/0xc0 drivers/media/common/videobuf2/videobuf2-v4l2.c:857 vivid_fop_release+0x18e/0x440 drivers/media/platform/vivid/vivid-core.c:474 v4l2_release+0xfb/0x1a0 drivers/media/v4l2-core/v4l2-dev.c:448 __fput+0x385/0xa30 fs/file_table.c:278 ____fput+0x15/0x20 fs/file_table.c:309 task_work_run+0x1e8/0x2a0 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:188 [inline] exit_to_usermode_loop+0x318/0x380 arch/x86/entry/common.c:166 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline] syscall_return_slowpath arch/x86/entry/common.c:268 [inline] do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x400f00 Code: 00 00 00 00 00 00 a8 01 00 00 00 00 00 00 36 01 00 00 b5 00 00 00 01 02 00 00 00 00 00 00 00 00 00 00 6a 01 00 00 00 00 00 00 <00> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 RSP: 002b:00007ffc53169f28 EFLAGS: 00000246 ORIG_RAX: 0000000000000003 RAX: 0000000000000000 RBX: 0000000000000003 RCX: 0000000000400f00 RDX: 00000000000000d6 RSI: 0000000020000140 RDI: 0000000000000003 RBP: 0000000000000000 R08: 00000000024b1880 R09: 00000000004002e0 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000003fc9c R13: 0000000000401ea0 R14: 0000000000000000 R15: 0000000000000000 INFO: task syz-executor686:5883 blocked for more than 140 seconds. Not tainted 4.19.0+ #309 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor686 D24208 5883 5718 0x00000004 Call Trace: context_switch kernel/sched/core.c:2831 [inline] __schedule+0x8cf/0x21d0 kernel/sched/core.c:3480 schedule+0xfe/0x460 kernel/sched/core.c:3524 schedule_timeout+0x1cc/0x260 kernel/time/timer.c:1780 do_wait_for_common kernel/sched/completion.c:83 [inline] __wait_for_common kernel/sched/completion.c:104 [inline] wait_for_common kernel/sched/completion.c:115 [inline] wait_for_completion+0x427/0x8a0 kernel/sched/completion.c:136 kthread_stop+0x1a9/0x900 kernel/kthread.c:550 vivid_stop_generating_vid_cap+0x2bc/0x93b drivers/media/platform/vivid/vivid-kthread-cap.c:919 vid_cap_stop_streaming+0x8d/0xe0 drivers/media/platform/vivid/vivid-vid-cap.c:256 __vb2_queue_cancel+0x171/0xca0 drivers/media/common/videobuf2/videobuf2-core.c:1659 vb2_core_streamoff+0x60/0x140 drivers/media/common/videobuf2/videobuf2-core.c:1795 __vb2_cleanup_fileio+0x73/0x160 drivers/media/common/videobuf2/videobuf2-core.c:2316 vb2_core_queue_release+0x1e/0x80 drivers/media/common/videobuf2/videobuf2-core.c:2043 vb2_queue_release drivers/media/common/videobuf2/videobuf2-v4l2.c:672 [inline] _vb2_fop_release+0x1d2/0x2b0 drivers/media/common/videobuf2/videobuf2-v4l2.c:843 vb2_fop_release+0x77/0xc0 drivers/media/common/videobuf2/videobuf2-v4l2.c:857 vivid_fop_release+0x18e/0x440 drivers/media/platform/vivid/vivid-core.c:474 v4l2_release+0xfb/0x1a0 drivers/media/v4l2-core/v4l2-dev.c:448 __fput+0x385/0xa30 fs/file_table.c:278 ____fput+0x15/0x20 fs/file_table.c:309 task_work_run+0x1e8/0x2a0 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:188 [inline] exit_to_usermode_loop+0x318/0x380 arch/x86/entry/common.c:166 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline] syscall_return_slowpath arch/x86/entry/common.c:268 [inline] do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x400f00 Code: 00 00 00 00 00 00 a8 01 00 00 00 00 00 00 36 01 00 00 b5 00 00 00 01 02 00 00 00 00 00 00 00 00 00 00 6a 01 00 00 00 00 00 00 <00> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 RSP: 002b:00007ffc53169f28 EFLAGS: 00000246 ORIG_RAX: 0000000000000003 RAX: 0000000000000000 RBX: 0000000000000003 RCX: 0000000000400f00 RDX: 00000000000000d6 RSI: 0000000020000140 RDI: 0000000000000003 RBP: 0000000000000000 R08: 00000000024b1880 R09: 00000000004002e0 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000003fca0 R13: 0000000000401ea0 R14: 0000000000000000 R15: 0000000000000000 Showing all locks held in the system: 1 lock held by khungtaskd/1008: #0: 00000000313d48c2 (rcu_read_lock){....}, at: debug_show_all_locks+0xd0/0x424 kernel/locking/lockdep.c:4379 2 locks held by rsyslogd/5598: #0: 00000000b3518de3 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0x1bb/0x200 fs/file.c:766 #1: 0000000038ba078b (logbuf_lock){-.-.}, at: is_bpf_text_address+0x0/0x170 kernel/bpf/core.c:533 2 locks held by getty/5688: #0: 0000000076b566f1 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353 #1: 00000000d605404c (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x335/0x1ce0 drivers/tty/n_tty.c:2140 2 locks held by getty/5689: #0: 0000000001bbb883 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353 #1: 00000000bd2d67d2 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x335/0x1ce0 drivers/tty/n_tty.c:2140 2 locks held by getty/5690: #0: 000000006d0f3ae6 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353 #1: 0000000043ffd330 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x335/0x1ce0 drivers/tty/n_tty.c:2140 2 locks held by getty/5691: #0: 000000007bbc59b2 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353 #1: 000000002498a126 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x335/0x1ce0 drivers/tty/n_tty.c:2140 2 locks held by getty/5692: #0: 000000007b579bf2 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353 #1: 000000002e537c6f (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x335/0x1ce0 drivers/tty/n_tty.c:2140 2 locks held by getty/5693: #0: 0000000034f4df10 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353 #1: 00000000d5e3a383 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x335/0x1ce0 drivers/tty/n_tty.c:2140 2 locks held by getty/5694: #0: 00000000b9babf44 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:353 #1: 0000000080bdfa70 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x335/0x1ce0 drivers/tty/n_tty.c:2140 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 1008 Comm: khungtaskd Not tainted 4.19.0+ #309 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x244/0x39d lib/dump_stack.c:113 nmi_cpu_backtrace.cold.1+0x5c/0xa1 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0x1b3/0x1ed lib/nmi_backtrace.c:62 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38 trigger_all_cpu_backtrace include/linux/nmi.h:144 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:204 [inline] watchdog+0xb3e/0x1050 kernel/hung_task.c:265 kthread+0x35a/0x440 kernel/kthread.c:246 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:350 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 skipped: idling at native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:57