syzbot
INFO: task hung in lo_open
Status:
public: reported C repro on 2019/04/11 00:00
Reported-by: syzbot+40a29aedacb650561903@syzkaller.appspotmail.com
First crash: 2898d, last: 2438d
Sample crash report:
INFO: task syz-executor193:1935 blocked for more than 140 seconds.
Not tainted 4.14.146+ #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor193 D28352 1935 1930 0x00000000
Call Trace:
schedule+0x92/0x1c0 kernel/sched/core.c:3498
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3556
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x595/0x13e0 kernel/locking/mutex.c:893
lo_open+0x19/0xb0 drivers/block/loop.c:1623
__blkdev_get+0x267/0xf90 fs/block_dev.c:1472
blkdev_get+0x97/0x8b0 fs/block_dev.c:1612
blkdev_open+0x1cc/0x250 fs/block_dev.c:1770
do_dentry_open+0x44e/0xe20 fs/open.c:789
vfs_open+0x105/0x230 fs/open.c:903
do_last fs/namei.c:3539 [inline]
path_openat+0xb6c/0x2be0 fs/namei.c:3681
do_filp_open+0x1a1/0x280 fs/namei.c:3715
do_sys_open+0x2ca/0x590 fs/open.c:1096
do_syscall_64+0x19b/0x520 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x4012a0
RSP: 002b:00007ffeaca73ee8 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 00000000000007d0 RCX: 00000000004012a0
RDX: 00007ffeaca73f0a RSI: 0000000000000002 RDI: 00007ffeaca73f00
RBP: 00000000000d759c R08: 0000000000000000 R09: 000000000000000a
R10: 0000000000000075 R11: 0000000000000246 R12: 00000000004022c0
R13: 0000000000402350 R14: 0000000000000000 R15: 0000000000000000
INFO: task syz-executor193:2006 blocked for more than 140 seconds.
Not tainted 4.14.146+ #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor193 D28352 2006 1934 0x00000004
Call Trace:
schedule+0x92/0x1c0 kernel/sched/core.c:3498
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3556
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x595/0x13e0 kernel/locking/mutex.c:893
lo_release+0x1b/0x1a0 drivers/block/loop.c:1666
__blkdev_put+0x518/0x6d0 fs/block_dev.c:1791
blkdev_close+0x86/0xb0 fs/block_dev.c:1863
__fput+0x25e/0x710 fs/file_table.c:210
task_work_run+0x125/0x1a0 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:191 [inline]
exit_to_usermode_loop+0x13b/0x160 arch/x86/entry/common.c:164
prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline]
syscall_return_slowpath arch/x86/entry/common.c:270 [inline]
do_syscall_64+0x3a3/0x520 arch/x86/entry/common.c:297
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x401240
RSP: 002b:00007ffeaca73ca8 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000401240
RDX: 0000000000000000 RSI: 0000000000004c01 RDI: 0000000000000005
RBP: 0000000000000004 R08: 0000000000000000 R09: 000000000000000c
R10: 0000000000000064 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000005 R14: 0000000000000000 R15: 0000000000000000
INFO: task syz-executor193:2011 blocked for more than 140 seconds.
Not tainted 4.14.146+ #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor193 D28336 2011 1936 0x00000004
Call Trace:
schedule+0x92/0x1c0 kernel/sched/core.c:3498
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3556
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x595/0x13e0 kernel/locking/mutex.c:893
blkdev_reread_part+0x1b/0x40 block/ioctl.c:192
loop_reread_partitions+0x7f/0x90 drivers/block/loop.c:614
loop_set_status+0xbff/0x11f0 drivers/block/loop.c:1183
loop_set_status64+0xa5/0x100 drivers/block/loop.c:1301
lo_ioctl+0xd1/0x1a30 drivers/block/loop.c:1431
__blkdev_driver_ioctl block/ioctl.c:297 [inline]
blkdev_ioctl+0x8d0/0x1870 block/ioctl.c:594
block_ioctl+0xd9/0x120 fs/block_dev.c:1881
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:500 [inline]
do_vfs_ioctl+0xabe/0x1040 fs/ioctl.c:684
SYSC_ioctl fs/ioctl.c:701 [inline]
SyS_ioctl+0x7f/0xb0 fs/ioctl.c:692
do_syscall_64+0x19b/0x520 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x4414b7
RSP: 002b:00007ffeaca73ca8 EFLAGS: 00000202 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00000000004414b7
RDX: 00007ffeaca73d40 RSI: 0000000000004c04 RDI: 0000000000000005
RBP: 0000000000000004 R08: 0000000000000000 R09: 000000000000000a
R10: 0000000000000075 R11: 0000000000000202 R12: 00000000004022c0
R13: 0000000000000005 R14: 0000000000000000 R15: 0000000000000000
INFO: task syz-executor193:2018 blocked for more than 140 seconds.
Not tainted 4.14.146+ #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor193 D28176 2018 1931 0x00000004
Call Trace:
schedule+0x92/0x1c0 kernel/sched/core.c:3498
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3556
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x595/0x13e0 kernel/locking/mutex.c:893
blkdev_reread_part+0x1b/0x40 block/ioctl.c:192
loop_reread_partitions+0x7f/0x90 drivers/block/loop.c:614
loop_set_status+0xbff/0x11f0 drivers/block/loop.c:1183
loop_set_status64+0xa5/0x100 drivers/block/loop.c:1301
lo_ioctl+0xd1/0x1a30 drivers/block/loop.c:1431
__blkdev_driver_ioctl block/ioctl.c:297 [inline]
blkdev_ioctl+0x8d0/0x1870 block/ioctl.c:594
block_ioctl+0xd9/0x120 fs/block_dev.c:1881
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:500 [inline]
do_vfs_ioctl+0xabe/0x1040 fs/ioctl.c:684
SYSC_ioctl fs/ioctl.c:701 [inline]
SyS_ioctl+0x7f/0xb0 fs/ioctl.c:692
do_syscall_64+0x19b/0x520 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x4414b7
RSP: 002b:00007ffeaca73ca8 EFLAGS: 00000202 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00000000004414b7
RDX: 00007ffeaca73d40 RSI: 0000000000004c04 RDI: 0000000000000005
RBP: 0000000000000004 R08: 0000000000000000 R09: 000000000000000a
R10: 0000000000000075 R11: 0000000000000202 R12: 00000000004022c0
R13: 0000000000000005 R14: 0000000000000000 R15: 0000000000000000
INFO: task blkid:2019 blocked for more than 140 seconds.
Not tainted 4.14.146+ #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
blkid D28448 2019 305 0x00000004
Call Trace:
schedule+0x92/0x1c0 kernel/sched/core.c:3498
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3556
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x595/0x13e0 kernel/locking/mutex.c:893
blkdev_put+0x27/0x4c0 fs/block_dev.c:1814
blkdev_close+0x86/0xb0 fs/block_dev.c:1863
__fput+0x25e/0x710 fs/file_table.c:210
task_work_run+0x125/0x1a0 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:191 [inline]
exit_to_usermode_loop+0x13b/0x160 arch/x86/entry/common.c:164
prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline]
syscall_return_slowpath arch/x86/entry/common.c:270 [inline]
do_syscall_64+0x3a3/0x520 arch/x86/entry/common.c:297
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x7f2d7e0982b0
RSP: 002b:00007ffd178e47d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00007f2d7e0982b0
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000015da030
R13: 0000000000000000 R14: 0000000000000003 R15: 0000000000000005
INFO: task blkid:2021 blocked for more than 140 seconds.
Not tainted 4.14.146+ #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
blkid D28336 2021 1940 0x00000004
Call Trace:
schedule+0x92/0x1c0 kernel/sched/core.c:3498
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3556
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x595/0x13e0 kernel/locking/mutex.c:893
lo_open+0x19/0xb0 drivers/block/loop.c:1623
__blkdev_get+0x267/0xf90 fs/block_dev.c:1472
blkdev_get+0x97/0x8b0 fs/block_dev.c:1612
blkdev_open+0x1cc/0x250 fs/block_dev.c:1770
do_dentry_open+0x44e/0xe20 fs/open.c:789
vfs_open+0x105/0x230 fs/open.c:903
do_last fs/namei.c:3539 [inline]
path_openat+0xb6c/0x2be0 fs/namei.c:3681
do_filp_open+0x1a1/0x280 fs/namei.c:3715
do_sys_open+0x2ca/0x590 fs/open.c:1096
do_syscall_64+0x19b/0x520 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x7fccae997120
RSP: 002b:00007ffed6e47de8 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fccae997120
RDX: 00007ffed6e49f41 RSI: 0000000000000000 RDI: 00007ffed6e49f41
RBP: 0000000000000000 R08: 0000000000000078 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000001784030
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000005
INFO: task syz-executor193:2024 blocked for more than 140 seconds.
Not tainted 4.14.146+ #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor193 D28240 2024 1933 0x00000004
Call Trace:
schedule+0x92/0x1c0 kernel/sched/core.c:3498
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3556
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x595/0x13e0 kernel/locking/mutex.c:893
loop_control_ioctl+0x183/0x310 drivers/block/loop.c:1996
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:500 [inline]
do_vfs_ioctl+0xabe/0x1040 fs/ioctl.c:684
SYSC_ioctl fs/ioctl.c:701 [inline]
SyS_ioctl+0x7f/0xb0 fs/ioctl.c:692
do_syscall_64+0x19b/0x520 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x4415a9
RSP: 002b:00007ffeaca73ee8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00000000004415a9
RDX: 0000000000000000 RSI: 0000000000004c81 RDI: 0000000000000003
RBP: 00000000000d74f9 R08: 0000000000000001 R09: 0000000000000001
R10: 0000000000000004 R11: 0000000000000246 R12: 00000000004022c0
R13: 0000000000402350 R14: 0000000000000000 R15: 0000000000000000
INFO: task blkid:2026 blocked for more than 140 seconds.
Not tainted 4.14.146+ #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
blkid D28448 2026 1945 0x00000004
Call Trace:
schedule+0x92/0x1c0 kernel/sched/core.c:3498
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3556
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x595/0x13e0 kernel/locking/mutex.c:893
lo_open+0x19/0xb0 drivers/block/loop.c:1623
__blkdev_get+0x963/0xf90 fs/block_dev.c:1537
blkdev_get+0x97/0x8b0 fs/block_dev.c:1612
blkdev_open+0x1cc/0x250 fs/block_dev.c:1770
do_dentry_open+0x44e/0xe20 fs/open.c:789
vfs_open+0x105/0x230 fs/open.c:903
do_last fs/namei.c:3539 [inline]
path_openat+0xb6c/0x2be0 fs/namei.c:3681
do_filp_open+0x1a1/0x280 fs/namei.c:3715
do_sys_open+0x2ca/0x590 fs/open.c:1096
do_syscall_64+0x19b/0x520 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x7f96bcbdd120
RSP: 002b:00007ffdfe2b1df8 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f96bcbdd120
RDX: 00007ffdfe2b3f41 RSI: 0000000000000000 RDI: 00007ffdfe2b3f41
RBP: 0000000000000000 R08: 0000000000000078 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000001e6e030
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000005
INFO: task blkid:2027 blocked for more than 140 seconds.
Not tainted 4.14.146+ #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
blkid D27808 2027 304 0x00000004
Call Trace:
schedule+0x92/0x1c0 kernel/sched/core.c:3498
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3556
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x595/0x13e0 kernel/locking/mutex.c:893
lo_open+0x19/0xb0 drivers/block/loop.c:1623
__blkdev_get+0x963/0xf90 fs/block_dev.c:1537
blkdev_get+0x97/0x8b0 fs/block_dev.c:1612
blkdev_open+0x1cc/0x250 fs/block_dev.c:1770
do_dentry_open+0x44e/0xe20 fs/open.c:789
vfs_open+0x105/0x230 fs/open.c:903
do_last fs/namei.c:3539 [inline]
path_openat+0xb6c/0x2be0 fs/namei.c:3681
do_filp_open+0x1a1/0x280 fs/namei.c:3715
do_sys_open+0x2ca/0x590 fs/open.c:1096
do_syscall_64+0x19b/0x520 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x7f964549c120
RSP: 002b:00007fffec5697b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f964549c120
RDX: 00007fffec56bf44 RSI: 0000000000000000 RDI: 00007fffec56bf44
RBP: 0000000000000000 R08: 0000000000000078 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000001787030
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000005
INFO: task blkid:2028 blocked for more than 140 seconds.
Not tainted 4.14.146+ #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
blkid D28464 2028 1944 0x00000004
Call Trace:
schedule+0x92/0x1c0 kernel/sched/core.c:3498
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3556
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0x595/0x13e0 kernel/locking/mutex.c:893
__blkdev_get+0xf3/0xf90 fs/block_dev.c:1457
blkdev_get+0x97/0x8b0 fs/block_dev.c:1612
blkdev_open+0x1cc/0x250 fs/block_dev.c:1770
do_dentry_open+0x44e/0xe20 fs/open.c:789
vfs_open+0x105/0x230 fs/open.c:903
do_last fs/namei.c:3539 [inline]
path_openat+0xb6c/0x2be0 fs/namei.c:3681
do_filp_open+0x1a1/0x280 fs/namei.c:3715
do_sys_open+0x2ca/0x590 fs/open.c:1096
do_syscall_64+0x19b/0x520 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x7f5c79113120
RSP: 002b:00007ffd249acb28 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f5c79113120
RDX: 00007ffd249adf41 RSI: 0000000000000000 RDI: 00007ffd249adf41
RBP: 0000000000000000 R08: 0000000000000078 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000139d030
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000005
Showing all locks held in the system:
1 lock held by khungtaskd/23:
#0: (tasklist_lock){.+.+}, at: [< (ptrval)>] debug_show_all_locks+0x7c/0x21a kernel/locking/lockdep.c:4541
1 lock held by rsyslogd/1633:
#0: (&f->f_pos_lock){+.+.}, at: [< (ptrval)>] __fdget_pos+0xb5/0xd0 fs/file.c:769
2 locks held by getty/1760:
#0: (&tty->ldisc_sem){++++}, at: [< (ptrval)>] tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:284
#1: (&ldata->atomic_read_lock){+.+.}, at: [< (ptrval)>] n_tty_read+0x1f7/0x1700 drivers/tty/n_tty.c:2156
2 locks held by syz-executor193/1935:
#0: (&bdev->bd_mutex){+.+.}, at: [< (ptrval)>] __blkdev_get+0xf3/0xf90 fs/block_dev.c:1457
#1: (loop_index_mutex){+.+.}, at: [< (ptrval)>] lo_open+0x19/0xb0 drivers/block/loop.c:1623
2 locks held by syz-executor193/2006:
#0: (&bdev->bd_mutex){+.+.}, at: [< (ptrval)>] __blkdev_put+0xb1/0x6d0 fs/block_dev.c:1778
#1: (loop_index_mutex){+.+.}, at: [< (ptrval)>] lo_release+0x1b/0x1a0 drivers/block/loop.c:1666
2 locks held by syz-executor193/2011:
#0: (&lo->lo_ctl_mutex/1){+.+.}, at: [< (ptrval)>] lo_ioctl+0x86/0x1a30 drivers/block/loop.c:1404
#1: (&bdev->bd_mutex){+.+.}, at: [< (ptrval)>] blkdev_reread_part+0x1b/0x40 block/ioctl.c:192
2 locks held by syz-executor193/2018:
#0: (&lo->lo_ctl_mutex/1){+.+.}, at: [< (ptrval)>] lo_ioctl+0x86/0x1a30 drivers/block/loop.c:1404
#1: (&bdev->bd_mutex){+.+.}, at: [< (ptrval)>] blkdev_reread_part+0x1b/0x40 block/ioctl.c:192
1 lock held by blkid/2019:
#0: (&bdev->bd_mutex){+.+.}, at: [< (ptrval)>] blkdev_put+0x27/0x4c0 fs/block_dev.c:1814
2 locks held by blkid/2021:
#0: (&bdev->bd_mutex){+.+.}, at: [< (ptrval)>] __blkdev_get+0xf3/0xf90 fs/block_dev.c:1457
#1: (loop_index_mutex){+.+.}, at: [< (ptrval)>] lo_open+0x19/0xb0 drivers/block/loop.c:1623
2 locks held by syz-executor193/2024:
#0: (loop_index_mutex){+.+.}, at: [< (ptrval)>] loop_control_ioctl+0x71/0x310 drivers/block/loop.c:1982
#1: (&lo->lo_ctl_mutex#2){+.+.}, at: [< (ptrval)>] loop_control_ioctl+0x183/0x310 drivers/block/loop.c:1996
2 locks held by blkid/2026:
#0: (&bdev->bd_mutex){+.+.}, at: [< (ptrval)>] __blkdev_get+0xf3/0xf90 fs/block_dev.c:1457
#1: (loop_index_mutex){+.+.}, at: [< (ptrval)>] lo_open+0x19/0xb0 drivers/block/loop.c:1623
2 locks held by blkid/2027:
#0: (&bdev->bd_mutex){+.+.}, at: [< (ptrval)>] __blkdev_get+0xf3/0xf90 fs/block_dev.c:1457
#1: (loop_index_mutex){+.+.}, at: [< (ptrval)>] lo_open+0x19/0xb0 drivers/block/loop.c:1623
1 lock held by blkid/2028:
#0: (&bdev->bd_mutex){+.+.}, at: [< (ptrval)>] __blkdev_get+0xf3/0xf90 fs/block_dev.c:1457
1 lock held by syz-executor193/2029:
#0: (loop_index_mutex){+.+.}, at: [< (ptrval)>] loop_control_ioctl+0x71/0x310 drivers/block/loop.c:1982
2 locks held by blkid/2030:
#0: (&bdev->bd_mutex){+.+.}, at: [< (ptrval)>] __blkdev_get+0xf3/0xf90 fs/block_dev.c:1457
#1: (loop_index_mutex){+.+.}, at: [< (ptrval)>] lo_open+0x19/0xb0 drivers/block/loop.c:1623
=============================================
NMI backtrace for cpu 0
CPU: 0 PID: 23 Comm: khungtaskd Not tainted 4.14.146+ #0
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0xca/0x134 lib/dump_stack.c:53
nmi_cpu_backtrace.cold+0x47/0x86 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x119/0x147 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:140 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:195 [inline]
watchdog+0x629/0xbe0 kernel/hung_task.c:274
kthread+0x31f/0x430 kernel/kthread.c:232
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:404
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at pc 0xffffffff94c9c503
Struck through repros no longer work on HEAD.