INFO: task syz.8.794:13538 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.8.794       state:D
 stack:25976 pid:13538 tgid:13537 ppid:12287  task_flags:0x400140 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5504 [inline]
 __schedule+0x16dc/0x5500 kernel/sched/core.c:7228
 __schedule_loop kernel/sched/core.c:7307 [inline]
 rt_mutex_schedule+0x76/0xf0 kernel/sched/core.c:7603
 rt_mutex_slowlock_block kernel/locking/rtmutex.c:1670 [inline]
 __rt_mutex_slowlock kernel/locking/rtmutex.c:1747 [inline]
 __rt_mutex_slowlock_locked+0x1f84/0x25b0 kernel/locking/rtmutex.c:1787
 __rwbase_read_lock+0xc3/0x180 kernel/locking/rwbase_rt.c:114
 rwbase_read_lock kernel/locking/rwbase_rt.c:147 [inline]
 __down_read kernel/locking/rwsem.c:1502 [inline]
 down_read+0x132/0x200 kernel/locking/rwsem.c:1576
 __super_lock fs/super.c:60 [inline]
 super_lock+0x2d6/0x3d0 fs/super.c:122
 __iterate_supers+0x120/0x240 fs/super.c:866
 ksys_sync fs/sync.c:102 [inline]
 __ia32_sys_sync+0xa0/0x120 fs/sync.c:111
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fa7bdc2ce59
RSP: 002b:00007fa7bbe86028 EFLAGS: 00000246 ORIG_RAX: 00000000000000a2
RAX: ffffffffffffffda RBX: 00007fa7bdea5fa0 RCX: 00007fa7bdc2ce59
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007fa7bdea5fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa7bdea6038 R14: 00007fa7bdea5fa0 R15: 00007ffea8e67af8
 </TASK>
INFO: lockdep is turned off.
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 37 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 nmi_cpu_backtrace+0x274/0x2d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x17a/0x300 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:162 [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+0x388/0x470 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
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 17 Comm: pr/legacy Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:io_serial_in+0x77/0xc0 drivers/tty/serial/8250/8250_port.c:401
Code: e8 6e 32 90 fc 44 89 f9 d3 e3 49 83 ee 80 4c 89 f0 48 c1 e8 03 42 80 3c 20 00 74 08 4c 89 f7 e8 3f 6b f7 fc 41 03 1e 89 da ec <0f> b6 c0 5b 41 5c 41 5e 41 5f c3 cc cc cc cc cc 44 89 f9 80 e1 07
RSP: 0018:ffffc90000167a08 EFLAGS: 00000202
RAX: 1ffffffff3321f00 RBX: 00000000000003fd RCX: 0000000000000000
RDX: 00000000000003fd RSI: 0000000000000000 RDI: 0000000000000000
RBP: dffffc0000000000 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: ffffffff85348930 R12: dffffc0000000000
R13: 0000000000000000 R14: ffffffff9990fa80 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff88812647d000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f77c8bf2000 CR3: 0000000055fba000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 serial_in drivers/tty/serial/8250/8250.h:128 [inline]
 serial_lsr_in drivers/tty/serial/8250/8250.h:150 [inline]
 wait_for_lsr+0x190/0x300 drivers/tty/serial/8250/8250_port.c:1973
 serial8250_fifo_wait_for_lsr_thre drivers/tty/serial/8250/8250_port.c:3210 [inline]
 serial8250_console_fifo_write drivers/tty/serial/8250/8250_port.c:3275 [inline]
 serial8250_console_write+0x1232/0x1bd0 drivers/tty/serial/8250/8250_port.c:3360
 console_emit_next_record kernel/printk/printk.c:3163 [inline]
 console_flush_one_record+0x642/0xb50 kernel/printk/printk.c:3269
 legacy_kthread_func+0x1b6/0x250 kernel/printk/printk.c:3712
 kthread+0x388/0x470 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
 </TASK>