From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753757AbeDARKD (ORCPT ); Sun, 1 Apr 2018 13:10:03 -0400 Received: from mail-io0-f198.google.com ([209.85.223.198]:44103 "EHLO mail-io0-f198.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753687AbeDARKC (ORCPT ); Sun, 1 Apr 2018 13:10:02 -0400 X-Google-Smtp-Source: AIpwx48icwTMWXfnLzBi04UqDpZGyPyBfIoyF3xc9lp2FAMCVV3eCEVEgQfJcRNzw1MggUjt/iwqGqc/4BiJxqgC1fU3jCIZiJ/S MIME-Version: 1.0 Date: Sun, 01 Apr 2018 10:10:01 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <94eb2c05b2d83650030568cc8bd9@google.com> Subject: INFO: task hung in wb_shutdown (2) From: syzbot To: axboe@kernel.dk, christophe.jaillet@wanadoo.fr, jack@suse.cz, linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com, zhangweiping@didichuxing.com Content-Type: text/plain; charset="UTF-8"; format=flowed; delsp=yes Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, syzbot hit the following crash on upstream commit 3eb2ce825ea1ad89d20f7a3b5780df850e4be274 (Sun Mar 25 22:44:30 2018 +0000) Linux 4.16-rc7 syzbot dashboard link: https://syzkaller.appspot.com/bug?extid=c0cf869505e03bdf1a24 So far this crash happened 179 times on upstream. Unfortunately, I don't have any reproducer for this crash yet. Raw console output: https://syzkaller.appspot.com/x/log.txt?id=4738516814659584 Kernel config: https://syzkaller.appspot.com/x/.config?id=-8440362230543204781 compiler: gcc (GCC) 7.1.1 20170620 IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+c0cf869505e03bdf1a24@syzkaller.appspotmail.com It will help syzbot understand when the bug is fixed. See footer for details. If you forward the report, please keep this part and the footer. unregister_netdevice: waiting for lo to become free. Usage count = 1 unregister_netdevice: waiting for lo to become free. Usage count = 1 unregister_netdevice: waiting for lo to become free. Usage count = 1 unregister_netdevice: waiting for lo to become free. Usage count = 1 unregister_netdevice: waiting for lo to become free. Usage count = 1 INFO: task kworker/0:5:16458 blocked for more than 120 seconds. Not tainted 4.16.0-rc7+ #368 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/0:5 D20928 16458 2 0x80000000 Workqueue: events cgwb_release_workfn Call Trace: context_switch kernel/sched/core.c:2862 [inline] __schedule+0x8fb/0x1ec0 kernel/sched/core.c:3440 schedule+0xf5/0x430 kernel/sched/core.c:3499 bit_wait+0x18/0x90 kernel/sched/wait_bit.c:250 __wait_on_bit+0x88/0x130 kernel/sched/wait_bit.c:51 out_of_line_wait_on_bit+0x204/0x3a0 kernel/sched/wait_bit.c:64 wait_on_bit include/linux/wait_bit.h:84 [inline] wb_shutdown+0x335/0x430 mm/backing-dev.c:377 cgwb_release_workfn+0x8b/0x61d mm/backing-dev.c:520 process_one_work+0xc47/0x1bb0 kernel/workqueue.c:2113 worker_thread+0x223/0x1990 kernel/workqueue.c:2247 kthread+0x33c/0x400 kernel/kthread.c:238 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:406 Showing all locks held in the system: 3 locks held by kworker/u4:1/21: #0: ((wq_completion)"%s""netns"){+.+.}, at: [<00000000c0d07d52>] work_static include/linux/workqueue.h:198 [inline] #0: ((wq_completion)"%s""netns"){+.+.}, at: [<00000000c0d07d52>] set_work_data kernel/workqueue.c:619 [inline] #0: ((wq_completion)"%s""netns"){+.+.}, at: [<00000000c0d07d52>] set_work_pool_and_clear_pending kernel/workqueue.c:646 [inline] #0: ((wq_completion)"%s""netns"){+.+.}, at: [<00000000c0d07d52>] process_one_work+0xb12/0x1bb0 kernel/workqueue.c:2084 #1: (net_cleanup_work){+.+.}, at: [<000000006c4c2cfd>] process_one_work+0xb89/0x1bb0 kernel/workqueue.c:2088 #2: (net_mutex){+.+.}, at: [<0000000058427774>] cleanup_net+0x242/0xcb0 net/core/net_namespace.c:484 2 locks held by khungtaskd/869: #0: (rcu_read_lock){....}, at: [<000000009066e5de>] check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: (rcu_read_lock){....}, at: [<000000009066e5de>] watchdog+0x1c5/0xd60 kernel/hung_task.c:249 #1: (tasklist_lock){.+.+}, at: [<000000002117cbd8>] debug_show_all_locks+0xd3/0x3d0 kernel/locking/lockdep.c:4470 2 locks held by getty/4407: #0: (&tty->ldisc_sem){++++}, at: [<0000000015dafb41>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000841085d3>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 2 locks held by getty/4408: #0: (&tty->ldisc_sem){++++}, at: [<0000000015dafb41>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000841085d3>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 2 locks held by getty/4409: #0: (&tty->ldisc_sem){++++}, at: [<0000000015dafb41>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000841085d3>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 2 locks held by getty/4410: #0: (&tty->ldisc_sem){++++}, at: [<0000000015dafb41>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000841085d3>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 2 locks held by getty/4411: #0: (&tty->ldisc_sem){++++}, at: [<0000000015dafb41>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000841085d3>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 2 locks held by getty/4412: #0: (&tty->ldisc_sem){++++}, at: [<0000000015dafb41>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000841085d3>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 2 locks held by getty/4413: #0: (&tty->ldisc_sem){++++}, at: [<0000000015dafb41>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000841085d3>] n_tty_read+0x2ef/0x1a40 drivers/tty/n_tty.c:2131 2 locks held by kworker/0:5/16458: #0: ((wq_completion)"events"){+.+.}, at: [<00000000c0d07d52>] work_static include/linux/workqueue.h:198 [inline] #0: ((wq_completion)"events"){+.+.}, at: [<00000000c0d07d52>] set_work_data kernel/workqueue.c:619 [inline] #0: ((wq_completion)"events"){+.+.}, at: [<00000000c0d07d52>] set_work_pool_and_clear_pending kernel/workqueue.c:646 [inline] #0: ((wq_completion)"events"){+.+.}, at: [<00000000c0d07d52>] process_one_work+0xb12/0x1bb0 kernel/workqueue.c:2084 #1: ((work_completion)(&wb->release_work)){+.+.}, at: [<000000006c4c2cfd>] process_one_work+0xb89/0x1bb0 kernel/workqueue.c:2088 1 lock held by syz-executor6/23709: #0: (net_mutex){+.+.}, at: [<00000000843d65a3>] copy_net_ns+0x1f5/0x580 net/core/net_namespace.c:417 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 869 Comm: khungtaskd Not tainted 4.16.0-rc7+ #368 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x194/0x24d lib/dump_stack.c:53 nmi_cpu_backtrace+0x1d2/0x210 lib/nmi_backtrace.c:103 nmi_trigger_cpumask_backtrace+0x123/0x180 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:138 [inline] check_hung_task kernel/hung_task.c:132 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:190 [inline] watchdog+0x90c/0xd60 kernel/hung_task.c:249 kthread+0x33c/0x400 kernel/kthread.c:238 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:406 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 skipped: idling at native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54 --- This bug is generated by a dumb bot. It may contain errors. See https://goo.gl/tpsmEJ for details. Direct all questions to syzkaller@googlegroups.com. syzbot will keep track of this bug report. If you forgot to add the Reported-by tag, once the fix for this bug is merged into any tree, please reply to this email with: #syz fix: exact-commit-title To mark this as a duplicate of another syzbot report, please reply with: #syz dup: exact-subject-of-another-report If it's a one-off invalid bug report, please reply with: #syz invalid Note: if the crash happens again, it will cause creation of a new bug report. Note: all commands must start from beginning of the line in the email body.