Not tainted 4.13.0-rc6-next-20170825+ #9 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syzkaller137134 D24216 3046 3040 0x00000004 Call Trace: context_switch kernel/sched/core.c:2792 [inline] __schedule+0x8e8/0x2070 kernel/sched/core.c:3371 schedule+0x108/0x440 kernel/sched/core.c:3430 __lock_sock+0x1dc/0x2f0 net/core/sock.c:2245 lock_sock_nested+0xf3/0x110 net/core/sock.c:2766 lock_sock include/net/sock.h:1459 [inline] tcp_sendmsg+0x21/0x50 net/ipv4/tcp.c:1447 inet_sendmsg+0x11f/0x5e0 net/ipv4/af_inet.c:762 sock_sendmsg_nosec net/socket.c:633 [inline] sock_sendmsg+0xca/0x110 net/socket.c:643 kernel_sendmsg+0x47/0x60 net/socket.c:651 sock_no_sendpage+0x1cc/0x280 net/core/sock.c:2574 tcp_sendpage_locked+0x10b/0x160 net/ipv4/tcp.c:1055 tcp_sendpage+0x43/0x60 net/ipv4/tcp.c:1070 inet_sendpage+0x1aa/0x660 net/ipv4/af_inet.c:779 kernel_sendpage+0x8d/0xe0 net/socket.c:3387 sock_sendpage+0x92/0xc0 net/socket.c:858 pipe_to_sendpage+0x290/0x3b0 fs/splice.c:467 splice_from_pipe_feed fs/splice.c:518 [inline] __splice_from_pipe+0x343/0x750 fs/splice.c:642 splice_from_pipe+0x1e9/0x330 fs/splice.c:677 generic_splice_sendpage+0x40/0x50 fs/splice.c:848 do_splice_from fs/splice.c:867 [inline] do_splice fs/splice.c:1163 [inline] SYSC_splice fs/splice.c:1418 [inline] SyS_splice+0x7d5/0x1630 fs/splice.c:1398 entry_SYSCALL_64_fastpath+0x1f/0xbe RIP: 0033:0x445469 RSP: 002b:00007f4df70cbdb8 EFLAGS: 00000212 ORIG_RAX: 0000000000000113 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000445469 RDX: 0000000000000005 RSI: 0000000000000000 RDI: 0000000000000003 RBP: 0000000000000086 R08: 000000000000001f R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000212 R12: 0000000000000000 R13: 00007ffff3c68f1f R14: 00007f4df70cc9c0 R15: 0000000000000000 Showing all locks held in the system: 2 locks held by khungtaskd/644: #0: (rcu_read_lock){....}, at: [] check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: (rcu_read_lock){....}, at: [] watchdog+0x1c5/0xd60 kernel/hung_task.c:249 #1: (tasklist_lock){.+.+}, at: [] debug_show_all_locks+0xd2/0x410 kernel/locking/lockdep.c:4552 2 locks held by getty/3013: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x2f2/0x1a40 drivers/tty/n_tty.c:2133 2 locks held by getty/3014: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x2f2/0x1a40 drivers/tty/n_tty.c:2133 2 locks held by getty/3015: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x2f2/0x1a40 drivers/tty/n_tty.c:2133 2 locks held by getty/3016: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x2f2/0x1a40 drivers/tty/n_tty.c:2133 2 locks held by getty/3017: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x2f2/0x1a40 drivers/tty/n_tty.c:2133 2 locks held by getty/3018: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x2f2/0x1a40 drivers/tty/n_tty.c:2133 2 locks held by getty/3019: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x2f2/0x1a40 drivers/tty/n_tty.c:2133 2 locks held by syzkaller137134/3046: #0: (&pipe->mutex/1){+.+.}, at: [] pipe_lock_nested fs/pipe.c:66 [inline] #0: (&pipe->mutex/1){+.+.}, at: [] pipe_lock fs/pipe.c:74 [inline] #0: (&pipe->mutex/1){+.+.}, at: [] pipe_wait+0x1e6/0x280 fs/pipe.c:122 #1: (sk_lock-AF_INET){+.+.}, at: [] lock_sock include/net/sock.h:1459 [inline] #1: (sk_lock-AF_INET){+.+.}, at: [] tcp_sendpage+0x2e/0x60 net/ipv4/tcp.c:1069 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 644 Comm: khungtaskd Not tainted 4.13.0-rc6-next-20170825+ #9 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:16 [inline] dump_stack+0x194/0x257 lib/dump_stack.c:52 nmi_cpu_backtrace+0x20e/0x240 lib/nmi_backtrace.c:102 nmi_trigger_cpumask_backtrace+0x122/0x180 lib/nmi_backtrace.c:61 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 trigger_all_cpu_backtrace include/linux/nmi.h:105 [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+0x39c/0x470 kernel/kthread.c:231 ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.13.0-rc6-next-20170825+ #9 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 task: ffff8801d9f8a300 task.stack: ffff8801d9f90000 RIP: 0010:trace_lock_release include/trace/events/lock.h:57 [inline] RIP: 0010:lock_release+0x1bf/0xd70 kernel/locking/lockdep.c:4020 RSP: 0018:ffff8801db307ca8 EFLAGS: 00000082 RAX: 0000000000000000 RBX: 1ffff1003b660f9a RCX: 0000000000000000 RDX: 0000000000000001 RSI: 0000000000000001 RDI: ffff8801d9f8ab94 RBP: ffff8801db307e58 R08: 0000000000000000 R09: 0000000000000001 R10: 0000000000000000 R11: ffffffff8707ac60 R12: ffff8801d9f8a300 R13: ffff8801db307e30 R14: ffffffff8707cc88 R15: ffff8801d9f8a300 FS: 0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000020844fe0 CR3: 00000001d3e48000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: seqcount_lockdep_reader_access include/linux/seqlock.h:81 [inline] read_seqcount_begin include/linux/seqlock.h:163 [inline] ktime_get+0x144/0x3a0 kernel/time/timekeeping.c:760 tick_nohz_irq_enter kernel/time/tick-sched.c:1144 [inline] tick_irq_enter+0x9e/0x390 kernel/time/tick-sched.c:1165 irq_enter+0xbd/0xe0 kernel/softirq.c:345 scheduler_ipi+0x8c/0x460 kernel/sched/core.c:1780 __smp_reschedule_interrupt arch/x86/kernel/smp.c:262 [inline] smp_reschedule_interrupt+0x61/0x80 arch/x86/kernel/smp.c:268 reschedule_interrupt+0x9d/0xb0 arch/x86/entry/entry_64.S:807 RIP: 0010:native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:53 RSP: 0018:ffff8801d9f97db0 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff02 RAX: dffffc0000000000 RBX: 1ffff1003b3f2fb9 RCX: 0000000000000000 RDX: 1ffffffff0b59188 RSI: 0000000000000001 RDI: ffffffff85ac8c40 RBP: ffff8801d9f97db0 R08: ffffffff85804a88 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff85ac8c30 R13: ffff8801d9f97e68 R14: 0000000000000000 R15: ffff8801d9f8a300 arch_safe_halt arch/x86/include/asm/paravirt.h:98 [inline] default_idle+0xbf/0x460 arch/x86/kernel/process.c:341 arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:332 default_idle_call+0x36/0x90 kernel/sched/idle.c:98 cpuidle_idle_call kernel/sched/idle.c:156 [inline] do_idle+0x256/0x3b0 kernel/sched/idle.c:246 cpu_startup_entry+0x18/0x20 kernel/sched/idle.c:351 start_secondary+0x277/0x310 arch/x86/kernel/smpboot.c:275 secondary_startup_64+0xa5/0xa5 arch/x86/kernel/head_64.S:235 Code: 93 08 00 00 41 c7 87 94 08 00 00 01 00 00 00 0f 1f 44 00 00 65 8b 05 a9 05 ac 7e 89 c0 48 0f a3 05 17 26 c9 04 0f 82 dc 07 00 00 <4d> 8d a5 00 ff ff ff 48 b8 00 00 00 00 00 fc ff df 49 c7 c7 00