Messages in this thread | | | From | Dmitry Vyukov <> | Date | Fri, 8 Jun 2018 10:20:15 +0200 | Subject | Re: INFO: task hung in netdev_run_todo |
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On Mon, Feb 12, 2018 at 11:03 AM, syzbot <syzbot+8cd13ab48843d67c58f0@syzkaller.appspotmail.com> wrote: > Hello, > > syzbot hit the following crash on upstream commit > 581e400ff935d34d95811258586128bf11baef15 (Wed Feb 7 22:29:34 2018 +0000) > Merge tag 'modules-for-v4.16' of > git://git.kernel.org/pub/scm/linux/kernel/git/jeyu/linux > > Unfortunately, I don't have any reproducer for this crash yet. > Raw console output is attached. > compiler: gcc (GCC) 7.1.1 20170620 > .config is attached. > user-space arch: i386 > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+8cd13ab48843d67c58f0@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. > > INFO: task kworker/u4:1:21 blocked for more than 120 seconds. > Not tainted 4.15.0+ #213 > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > kworker/u4:1 D12208 21 2 0x80000000 > Workqueue: netns cleanup_net > Call Trace: > context_switch kernel/sched/core.c:2857 [inline] > __schedule+0x8e2/0x2040 kernel/sched/core.c:3435 > schedule+0xf5/0x430 kernel/sched/core.c:3494 > schedule_preempt_disabled+0x10/0x20 kernel/sched/core.c:3552 > __mutex_lock_common kernel/locking/mutex.c:833 [inline] > __mutex_lock+0xaad/0x1a80 kernel/locking/mutex.c:893 > mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 > rtnl_lock+0x17/0x20 net/core/rtnetlink.c:74 > netdev_wait_allrefs+0x1cb/0x410 net/core/dev.c:8035 > netdev_run_todo+0x478/0xae0 net/core/dev.c:8129 > rtnl_unlock+0xe/0x10 net/core/rtnetlink.c:108 > default_device_exit_batch+0x4b4/0x5d0 net/core/dev.c:8930 > ops_exit_list.isra.6+0x100/0x150 net/core/net_namespace.c:145 > cleanup_net+0x6a3/0xcc0 net/core/net_namespace.c:517 > process_one_work+0xbbf/0x1af0 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:429 > > Showing all locks held in the system: > 4 locks held by kworker/u4:1/21: > #0: ((wq_completion)"%s""netns"){+.+.}, at: [<000000008671663e>] > process_one_work+0xaaf/0x1af0 kernel/workqueue.c:2084 > #1: (net_cleanup_work){+.+.}, at: [<0000000098e1951b>] > process_one_work+0xb01/0x1af0 kernel/workqueue.c:2088 > #2: (net_mutex){+.+.}, at: [<000000009da3dcc8>] cleanup_net+0x242/0xcc0 > net/core/net_namespace.c:484 > #3: (rtnl_mutex){+.+.}, at: [<000000000b60ddd2>] rtnl_lock+0x17/0x20 > net/core/rtnetlink.c:74 > 2 locks held by khungtaskd/758: > #0: (rcu_read_lock){....}, at: [<0000000032c7899a>] > check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] > #0: (rcu_read_lock){....}, at: [<0000000032c7899a>] watchdog+0x1c5/0xd60 > kernel/hung_task.c:249 > #1: (tasklist_lock){.+.+}, at: [<000000008744ddaf>] > debug_show_all_locks+0xd3/0x3d0 kernel/locking/lockdep.c:4470 > 1 lock held by rsyslogd/3947: > #0: (&f->f_pos_lock){+.+.}, at: [<00000000f50ca942>] > __fdget_pos+0x12b/0x190 fs/file.c:765 > 2 locks held by getty/4070: > #0: (&tty->ldisc_sem){++++}, at: [<000000004fdd9acb>] > ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 > #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000033740686>] > n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 > 2 locks held by getty/4071: > #0: (&tty->ldisc_sem){++++}, at: [<000000004fdd9acb>] > ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 > #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000033740686>] > n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 > 2 locks held by getty/4072: > #0: (&tty->ldisc_sem){++++}, at: [<000000004fdd9acb>] > ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 > #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000033740686>] > n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 > 2 locks held by getty/4073: > #0: (&tty->ldisc_sem){++++}, at: [<000000004fdd9acb>] > ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 > #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000033740686>] > n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 > 2 locks held by getty/4074: > #0: (&tty->ldisc_sem){++++}, at: [<000000004fdd9acb>] > ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 > #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000033740686>] > n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 > 2 locks held by getty/4075: > #0: (&tty->ldisc_sem){++++}, at: [<000000004fdd9acb>] > ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 > #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000033740686>] > n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 > 2 locks held by getty/4076: > #0: (&tty->ldisc_sem){++++}, at: [<000000004fdd9acb>] > ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 > #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000033740686>] > n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 > 1 lock held by syz-executor2/4154: > #0: (rtnl_mutex){+.+.}, at: [<000000000b60ddd2>] rtnl_lock+0x17/0x20 > net/core/rtnetlink.c:74 > 3 locks held by kworker/1:3/7524: > #0: ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at: [<000000008671663e>] > process_one_work+0xaaf/0x1af0 kernel/workqueue.c:2084 > #1: ((addr_chk_work).work){+.+.}, at: [<0000000098e1951b>] > process_one_work+0xb01/0x1af0 kernel/workqueue.c:2088 > #2: (rtnl_mutex){+.+.}, at: [<000000000b60ddd2>] rtnl_lock+0x17/0x20 > net/core/rtnetlink.c:74 > 1 lock held by syz-executor0/10595: > #0: (rtnl_mutex){+.+.}, at: [<000000000b60ddd2>] rtnl_lock+0x17/0x20 > net/core/rtnetlink.c:74 > 1 lock held by syz-executor3/13841: > #0: (sk_lock-AF_INET6){+.+.}, at: [<0000000063f9b07b>] lock_sock > include/net/sock.h:1463 [inline] > #0: (sk_lock-AF_INET6){+.+.}, at: [<0000000063f9b07b>] > compat_ipv6_getsockopt+0x1f1/0x390 net/ipv6/ipv6_sockglue.c:1412 > 1 lock held by syz-executor3/13845: > #0: (rtnl_mutex){+.+.}, at: [<000000000b60ddd2>] rtnl_lock+0x17/0x20 > net/core/rtnetlink.c:74 > 1 lock held by syz-executor3/13851: > #0: (rtnl_mutex){+.+.}, at: [<000000000b60ddd2>] rtnl_lock+0x17/0x20 > net/core/rtnetlink.c:74 > 1 lock held by syz-executor3/13862: > #0: (rtnl_mutex){+.+.}, at: [<000000000b60ddd2>] rtnl_lock+0x17/0x20 > net/core/rtnetlink.c:74 > 1 lock held by syz-executor0/13866: > #0: (rtnl_mutex){+.+.}, at: [<000000000b60ddd2>] rtnl_lock+0x17/0x20 > net/core/rtnetlink.c:74 > 1 lock held by syz-executor2/13868: > #0: (rtnl_mutex){+.+.}, at: [<000000000b60ddd2>] rtnl_lock+0x17/0x20 > net/core/rtnetlink.c:74 > > ============================================= > > NMI backtrace for cpu 1 > CPU: 1 PID: 758 Comm: khungtaskd Not tainted 4.15.0+ #213 > 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+0x194/0x257 lib/dump_stack.c:53 > nmi_cpu_backtrace+0x1d2/0x210 lib/nmi_backtrace.c:103 > nmi_trigger_cpumask_backtrace+0x122/0x180 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:429 > Sending NMI from CPU 1 to CPUs 0: > NMI backtrace for cpu 0 > CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.15.0+ #213 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > Google 01/01/2011 > RIP: 0010:rcu_lockdep_current_cpu_online+0x52/0x190 kernel/rcu/tree.c:1123 > RSP: 0018:ffff8801db407780 EFLAGS: 00000282 > RAX: ffffed003b680ef0 RBX: 1ffff1003b680ef0 RCX: 1ffff1003b680ef6 > RDX: dffffc0000000000 RSI: ffffffff86b290c0 RDI: ffff8801db423750 > RBP: ffff8801db407808 R08: 1ffff1003b680e47 R09: 0000000000000002 > R10: ffff8801db4076f8 R11: 0000000000000020 R12: 1ffff1003b680f20 > R13: ffff8801d9e66a00 R14: ffff8801db4079c0 R15: 1ffff1003b680f14 > FS: 0000000000000000(0000) GS:ffff8801db400000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 000000000240f000 CR3: 0000000006a22003 CR4: 00000000001606f0 > DR0: 0000000020000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600 > Call Trace: > <IRQ> > rcu_read_lock_held+0x94/0xc0 kernel/rcu/update.c:331 > rebalance_domains+0x945/0xcc0 kernel/sched/fair.c:9147 > run_rebalance_domains+0x378/0x770 kernel/sched/fair.c:9405 > __do_softirq+0x2d7/0xb85 kernel/softirq.c:285 > invoke_softirq kernel/softirq.c:365 [inline] > irq_exit+0x1cc/0x200 kernel/softirq.c:405 > scheduler_ipi+0x318/0x820 kernel/sched/core.c:1804 > smp_reschedule_interrupt+0xe6/0x650 arch/x86/kernel/smp.c:277 > reschedule_interrupt+0xa9/0xb0 arch/x86/entry/entry_64.S:853 > </IRQ> > RIP: 0010:native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54 > RSP: 0018:ffffffff86a07c38 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff02 > RAX: dffffc0000000000 RBX: 1ffffffff0d40f8a RCX: 0000000000000000 > RDX: 1ffffffff0d59278 RSI: 0000000000000001 RDI: ffffffff86ac93c0 > RBP: ffffffff86a07c38 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 > R13: ffffffff86a07cf0 R14: ffffffff87269560 R15: 0000000000000000 > arch_safe_halt arch/x86/include/asm/paravirt.h:93 [inline] > default_idle+0xbf/0x430 arch/x86/kernel/process.c:354 > arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:345 > default_idle_call+0x36/0x90 kernel/sched/idle.c:98 > cpuidle_idle_call kernel/sched/idle.c:156 [inline] > do_idle+0x24a/0x3b0 kernel/sched/idle.c:246 > cpu_startup_entry+0x104/0x120 kernel/sched/idle.c:351 > rest_init+0xed/0xf0 init/main.c:436 > start_kernel+0x7f1/0x819 init/main.c:716 > x86_64_start_reservations+0x2a/0x2c arch/x86/kernel/head64.c:378 > x86_64_start_kernel+0x77/0x7a arch/x86/kernel/head64.c:359 > secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:237 > Code: c7 85 78 ff ff ff b3 8a b5 41 48 8d 04 13 48 c7 45 80 b5 14 7d 86 48 > c7 45 88 50 e2 5d 81 c7 00 f1 f1 f1 f1 c7 40 04 00 f2 f2 f2 <c7> 40 08 f3 f3 > f3 f3 b8 01 00 00 00 65 8b 0d 9b 0a a4 7e 81 e1
Presumably this is just a flake due to too slow execution. A thread can't actually take the mutex for 2 minutes, but nothing has hanged entirely. See detailed discussion here: https://groups.google.com/d/msg/syzkaller-bugs/JwoXRjOYNnY/pIZWcXAoBQAJ
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