INFO: task syz.0.16563:22795 blocked for more than 143 seconds.
Tainted: G L syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.16563 state:D stack:26488 pid:22795 tgid:22794 ppid:5620 task_flags:0x400140 flags:0x08080002
Call Trace:
context_switch kernel/sched/core.c:5520 [inline]
__schedule+0x17db/0x58f0 kernel/sched/core.c:7270
__schedule_loop kernel/sched/core.c:7347 [inline]
schedule+0x164/0x2b0 kernel/sched/core.c:7362
cgroup_lock_and_drain_offline+0x51a/0x650 kernel/cgroup/cgroup.c:3350
cgroup_kn_lock_live+0x120/0x230 kernel/cgroup/cgroup.c:1717
cgroup_subtree_control_write+0x4b5/0x1080 kernel/cgroup/cgroup.c:3652
cgroup_file_write+0x331/0x8f0 kernel/cgroup/cgroup.c:4412
kernfs_fop_write_iter+0x3a4/0x540 fs/kernfs/file.c:345
new_sync_write fs/read_write.c:595 [inline]
vfs_write+0x612/0xba0 fs/read_write.c:687
ksys_write+0x150/0x270 fs/read_write.c:739
do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:79 [inline]
__do_fast_syscall_32+0x27a/0x6a0 arch/x86/entry/syscall_32.c:291
do_fast_syscall_32+0x33/0x70 arch/x86/entry/syscall_32.c:316
entry_SYSENTER_compat_after_hwframe+0x84/0x8e
RIP: 0023:0xf709f0ec
RSP: 002b:00000000f548d50c EFLAGS: 00000206 ORIG_RAX: 0000000000000004
RAX: ffffffffffffffda RBX: 0000000000000008 RCX: 0000000080000300
RDX: 0000000000000005 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
Showing all locks held in the system:
locks held by pr/ttyS0/16: 2, last CPU#1:
#0: ffffffff8ec362b8 (console_srcu){....}-{0:0}, at: rcu_try_lock_acquire include/linux/rcupdate.h:314 [inline]
#0: ffffffff8ec362b8 (console_srcu){....}-{0:0}, at: srcu_read_lock_nmisafe include/linux/srcu.h:439 [inline]
#0: ffffffff8ec362b8 (console_srcu){....}-{0:0}, at: console_srcu_read_lock+0x30/0x60 kernel/printk/printk.c:291
#1: ffffffff9ad31098 (&port_lock_key){-.-.}-{3:3}, at: __uart_port_lock_irqsave include/linux/serial_core.h:613 [inline]
#1: ffffffff9ad31098 (&port_lock_key){-.-.}-{3:3}, at: univ8250_console_device_lock+0x67/0xc0 drivers/tty/serial/8250/8250_core.c:413
locks held by khungtaskd/32: 1, last CPU#0:
#0: ffffffff8ed5c6e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
#0: ffffffff8ed5c6e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
#0: ffffffff8ed5c6e0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6837
locks held by getty/5376: 2, on CPU#1:
#0: ffff88803618b0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
#1: ffffc9000322b2e8 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x45a/0x1360 drivers/tty/n_tty.c:2211
locks held by syz.0.16563/22795: 3, on CPU#1:
#0: ffff88807fe5bb30 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x246/0x320 fs/file.c:1259
#1: ffff8880357d2460 (sb_writers#9){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2753 [inline]
#1: ffff8880357d2460 (sb_writers#9){.+.+}-{0:0}, at: vfs_write+0x22b/0xba0 fs/read_write.c:683
#2: ffff888056e42080 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1d8/0x540 fs/kernfs/file.c:336
=============================================
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 32 Comm: khungtaskd Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
nmi_cpu_backtrace+0x274/0x2d0 lib/nmi_backtrace.c:123
nmi_trigger_cpumask_backtrace+0x17d/0x390 lib/nmi_backtrace.c:66
trigger_all_cpu_backtrace include/linux/nmi.h:164 [inline]
__sys_info lib/sys_info.c:157 [inline]
sys_info+0x135/0x170 lib/sys_info.c:165
check_hung_uninterruptible_tasks kernel/hung_task.c:353 [inline]
watchdog+0xfd7/0x1030 kernel/hung_task.c:561
kthread+0x38b/0x480 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 16 Comm: pr/ttyS0 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:delay_tsc+0x5d/0xd0 arch/x86/lib/delay.c:77
Code: 89 d7 49 c1 e7 20 49 09 c7 4d 29 f7 49 39 df 73 55 bf 01 00 00 00 e8 52 76 b2 f5 65 48 8b 05 fa f8 b1 07 48 85 c0 74 1c f3 90 01 00 00 00 e8 e9 74 b2 f5 e8 84 7a 01 00 39 c5 75 0e 0f 01 f9
RSP: 0018:ffffc900001578b8 EFLAGS: 00000082
RAX: 8000000000000001 RBX: 0000000000000899 RCX: ffffffff9a9da501
RDX: 0000000000000401 RSI: ffffffff8c6d9360 RDI: 00000000ffffffff
RBP: 0000000000000001 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: ffffffff8be266c0 R12: 1ffffffff35a626d
R13: 00000000ffffffff R14: 000004fd3650ac30 R15: 000000000000024c
FS: 0000000000000000(0000) GS:ffff888124dda000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000560e0d676a38 CR3: 000000000eb48000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000008f06 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
udelay include/asm-generic/delay.h:62 [inline]
wait_for_lsr+0x147/0x2f0 drivers/tty/serial/8250/8250_port.c:2019
serial8250_fifo_wait_for_lsr_thre drivers/tty/serial/8250/8250_port.c:3270 [inline]
__serial8250_console_fifo_write+0xcd/0x3e0 drivers/tty/serial/8250/8250_port.c:3345
serial8250_console_fifo_write drivers/tty/serial/8250/8250_port.c:3378 [inline]
__serial8250_console_write drivers/tty/serial/8250/8250_port.c:3429 [inline]
serial8250_console_write+0xaa1/0x1200 drivers/tty/serial/8250/8250_port.c:3493
nbcon_emit_next_record+0xef5/0x1a90 kernel/printk/nbcon.c:-1
nbcon_emit_one kernel/printk/nbcon.c:1157 [inline]
nbcon_kthread_func+0x679/0x880 kernel/printk/nbcon.c:1271
kthread+0x38b/0x480 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245