------------[ cut here ]------------
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G             L     
------------------------------------------------------
syz.3.1370/12400 is trying to acquire lock:
ffffffff8df35980 (console_owner){-.-.}-{0:0}, at: console_trylock_spinning kernel/printk/printk.c:2024 [inline]
ffffffff8df35980 (console_owner){-.-.}-{0:0}, at: vprintk_emit+0x321/0x5f0 kernel/printk/printk.c:2425

but task is already holding lock:
ffff8880b863a918 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0xad/0x140 kernel/sched/core.c:647

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #4 (&rq->__lock){-.-.}-{2:2}:
       _raw_spin_lock_nested+0x32/0x50 kernel/locking/spinlock.c:378
       raw_spin_rq_lock_nested+0x2a/0x140 kernel/sched/core.c:639
       raw_spin_rq_lock kernel/sched/sched.h:1556 [inline]
       task_rq_lock+0xbc/0x470 kernel/sched/core.c:739
       cgroup_move_task+0x92/0x2a0 kernel/sched/psi.c:1170
       css_set_move_task+0x658/0x9e0 kernel/cgroup/cgroup.c:951
       cgroup_post_fork+0x1ef/0x7a0 kernel/cgroup/cgroup.c:6913
       copy_process+0x3614/0x3950 kernel/fork.c:2465
       kernel_clone+0x21e/0x820 kernel/fork.c:2651
       user_mode_thread+0xdd/0x140 kernel/fork.c:2727
       rest_init+0x23/0x300 init/main.c:722
       start_kernel+0x3a7/0x400 init/main.c:1206
       x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310
       x86_64_start_kernel+0x143/0x1c0 arch/x86/kernel/head64.c:291
       common_startup_64+0x13e/0x147

-> #3 (&p->pi_lock){-.-.}-{2:2}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0xa7/0xf0 kernel/locking/spinlock.c:162
       class_raw_spinlock_irqsave_constructor include/linux/spinlock.h:557 [inline]
       try_to_wake_up+0x67/0x12b0 kernel/sched/core.c:4108
       __wake_up_common kernel/sched/wait.c:108 [inline]
       __wake_up_common_lock+0x137/0x1f0 kernel/sched/wait.c:125
       tty_port_default_wakeup+0xfb/0x170 drivers/tty/tty_port.c:67
       serial8250_tx_chars+0x72e/0x970 drivers/tty/serial/8250/8250_port.c:1719
       serial8250_handle_irq+0x633/0xbb0 drivers/tty/serial/8250/8250_port.c:1827
       serial8250_default_handle_irq+0xbf/0x200 drivers/tty/serial/8250/8250_port.c:1846
       serial8250_interrupt+0x8d/0x180 drivers/tty/serial/8250/8250_core.c:86
       __handle_irq_event_percpu+0x285/0xa60 kernel/irq/handle.c:211
       handle_irq_event_percpu kernel/irq/handle.c:248 [inline]
       handle_irq_event+0x8b/0x1e0 kernel/irq/handle.c:265
       handle_edge_irq+0x23b/0xa10 kernel/irq/chip.c:855
       generic_handle_irq_desc include/linux/irqdesc.h:172 [inline]
       handle_irq arch/x86/kernel/irq.c:255 [inline]
       call_irq_handler arch/x86/kernel/irq.c:-1 [inline]
       __common_interrupt+0x141/0x1f0 arch/x86/kernel/irq.c:326
       common_interrupt+0x5e/0xe0 arch/x86/kernel/irq.c:319
       asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:688
       on_stack arch/x86/include/asm/stacktrace.h:60 [inline]
       stack_access_ok arch/x86/kernel/unwind_orc.c:409 [inline]
       deref_stack_reg arch/x86/kernel/unwind_orc.c:419 [inline]
       unwind_next_frame+0xd80/0x23d0 arch/x86/kernel/unwind_orc.c:600
       arch_stack_walk+0x11c/0x150 arch/x86/kernel/stacktrace.c:25
       stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
       kasan_save_stack mm/kasan/common.c:57 [inline]
       kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
       kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584
       poison_slab_object mm/kasan/common.c:253 [inline]
       __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
       kasan_slab_free include/linux/kasan.h:235 [inline]
       slab_free_hook mm/slub.c:2540 [inline]
       slab_free mm/slub.c:6670 [inline]
       kfree+0x1c0/0x660 mm/slub.c:6878
       slab_free_after_rcu_debug+0x5d/0x260 mm/slub.c:6716
       rcu_do_batch kernel/rcu/tree.c:2605 [inline]
       rcu_core+0xd70/0x1870 kernel/rcu/tree.c:2857
       handle_softirqs+0x27d/0x850 kernel/softirq.c:626
       __do_softirq kernel/softirq.c:660 [inline]
       invoke_softirq kernel/softirq.c:496 [inline]
       __irq_exit_rcu+0xca/0x1f0 kernel/softirq.c:727
       irq_exit_rcu+0x9/0x30 kernel/softirq.c:743
       instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1056 [inline]
       sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1056
       asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
       arch_atomic64_read arch/x86/include/asm/atomic64_64.h:15 [inline]
       raw_atomic64_read include/linux/atomic/atomic-arch-fallback.h:2583 [inline]
       raw_atomic_long_read include/linux/atomic/atomic-long.h:38 [inline]
       atomic_long_read include/linux/atomic/atomic-instrumented.h:3189 [inline]
       netdev_stats_to_stats64 net/core/dev.c:11780 [inline]
       dev_get_stats+0x4b3/0xa50 net/core/dev.c:11859
       rtnl_fill_stats+0x47/0x8c0 net/core/rtnetlink.c:1484
       rtnl_fill_ifinfo+0x1719/0x1fa0 net/core/rtnetlink.c:2133
       rtnl_dump_ifinfo+0xaa0/0x1070 net/core/rtnetlink.c:2514
       rtnl_dumpit+0xa2/0x200 net/core/rtnetlink.c:6827
       netlink_dump+0x6e4/0xe90 net/netlink/af_netlink.c:2325
       netlink_recvmsg+0x676/0xa30 net/netlink/af_netlink.c:1976
       sock_recvmsg_nosec+0x186/0x1c0 net/socket.c:1093
       ____sys_recvmsg+0x21e/0x4c0 net/socket.c:-1
       ___sys_recvmsg+0x1b5/0x510 net/socket.c:2872
       __sys_recvmsg net/socket.c:2905 [inline]
       __do_sys_recvmsg net/socket.c:2911 [inline]
       __se_sys_recvmsg net/socket.c:2908 [inline]
       __x64_sys_recvmsg+0x198/0x260 net/socket.c:2908
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (&tty->write_wait){-.-.}-{3:3}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0xa7/0xf0 kernel/locking/spinlock.c:162
       __wake_up_common_lock+0x2f/0x1f0 kernel/sched/wait.c:124
       tty_port_default_wakeup+0xfb/0x170 drivers/tty/tty_port.c:67
       serial8250_tx_chars+0x72e/0x970 drivers/tty/serial/8250/8250_port.c:1719
       serial8250_handle_irq+0x633/0xbb0 drivers/tty/serial/8250/8250_port.c:1827
       serial8250_default_handle_irq+0xbf/0x200 drivers/tty/serial/8250/8250_port.c:1846
       serial8250_interrupt+0x8d/0x180 drivers/tty/serial/8250/8250_core.c:86
       __handle_irq_event_percpu+0x285/0xa60 kernel/irq/handle.c:211
       handle_irq_event_percpu kernel/irq/handle.c:248 [inline]
       handle_irq_event+0x8b/0x1e0 kernel/irq/handle.c:265
       handle_edge_irq+0x23b/0xa10 kernel/irq/chip.c:855
       generic_handle_irq_desc include/linux/irqdesc.h:172 [inline]
       handle_irq arch/x86/kernel/irq.c:255 [inline]
       call_irq_handler arch/x86/kernel/irq.c:-1 [inline]
       __common_interrupt+0x141/0x1f0 arch/x86/kernel/irq.c:326
       common_interrupt+0xb6/0xe0 arch/x86/kernel/irq.c:319
       asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:688
       __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
       _raw_spin_unlock_irqrestore+0xa8/0x110 kernel/locking/spinlock.c:194
       spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
       uart_port_unlock_irqrestore include/linux/serial_core.h:788 [inline]
       uart_port_unlock_deref+0x111/0x2f0 drivers/tty/serial/serial_core.c:91
       uart_write+0xe8/0x130 drivers/tty/serial/serial_core.c:634
       process_output_block drivers/tty/n_tty.c:557 [inline]
       n_tty_write+0xd78/0x12a0 drivers/tty/n_tty.c:2366
       iterate_tty_write drivers/tty/tty_io.c:1006 [inline]
       file_tty_write+0x559/0xa20 drivers/tty/tty_io.c:1081
       new_sync_write fs/read_write.c:593 [inline]
       vfs_write+0x5c9/0xb30 fs/read_write.c:686
       ksys_write+0x145/0x250 fs/read_write.c:738
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&port_lock_key){-.-.}-{3:3}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0xa7/0xf0 kernel/locking/spinlock.c:162
       uart_port_lock_irqsave include/linux/serial_core.h:717 [inline]
       serial8250_console_write+0x17e/0x1ba0 drivers/tty/serial/8250/8250_port.c:3301
       console_emit_next_record kernel/printk/printk.c:3129 [inline]
       console_flush_one_record kernel/printk/printk.c:3215 [inline]
       console_flush_all+0x745/0xb60 kernel/printk/printk.c:3289
       __console_flush_and_unlock kernel/printk/printk.c:3319 [inline]
       console_unlock+0xbb/0x190 kernel/printk/printk.c:3359
       vprintk_emit+0x4f8/0x5f0 kernel/printk/printk.c:2426
       _printk+0xcf/0x120 kernel/printk/printk.c:2451
       register_console+0xa8b/0xf90 kernel/printk/printk.c:4170
       univ8250_console_init+0x3a/0x70 drivers/tty/serial/8250/8250_core.c:515
       console_init+0xfc/0x3f0 kernel/printk/printk.c:4369
       start_kernel+0x24d/0x400 init/main.c:1143
       x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310
       x86_64_start_kernel+0x143/0x1c0 arch/x86/kernel/head64.c:291
       common_startup_64+0x13e/0x147

-> #0 (console_owner){-.-.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3165 [inline]
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x15a6/0x2cf0 kernel/locking/lockdep.c:5237
       lock_acquire+0x117/0x340 kernel/locking/lockdep.c:5868
       console_trylock_spinning kernel/printk/printk.c:2024 [inline]
       vprintk_emit+0x33d/0x5f0 kernel/printk/printk.c:2425
       _printk+0xcf/0x120 kernel/printk/printk.c:2451
       __report_bug+0x305/0x500 lib/bug.c:243
       report_bug+0x16a/0x220 lib/bug.c:281
       handle_bug+0x98/0x200 arch/x86/kernel/traps.c:435
       exc_invalid_op+0x1a/0x50 arch/x86/kernel/traps.c:489
       asm_exc_invalid_op+0x1a/0x20 arch/x86/include/asm/idtentry.h:616
       sched_change_end+0x4f6/0x640 kernel/sched/core.c:10851
       class_sched_change_destructor kernel/sched/sched.h:3956 [inline]
       rt_mutex_setprio+0x488/0xb70 kernel/sched/core.c:7331
       rt_mutex_adjust_prio kernel/locking/rtmutex.c:539 [inline]
       remove_waiter+0x7f5/0xaf0 kernel/locking/rtmutex.c:1567
       rt_mutex_cleanup_proxy_lock+0x6c/0x100 kernel/locking/rtmutex_api.c:458
       futex_wait_requeue_pi+0x481/0x850 kernel/futex/requeue.c:865
       do_futex+0x181/0x420 kernel/futex/syscalls.c:153
       __do_sys_futex kernel/futex/syscalls.c:207 [inline]
       __se_sys_futex+0x36f/0x400 kernel/futex/syscalls.c:188
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  console_owner --> &p->pi_lock --> &rq->__lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&rq->__lock);
                               lock(&p->pi_lock);
                               lock(&rq->__lock);
  lock(console_owner);

 *** DEADLOCK ***

3 locks held by syz.3.1370/12400:
 #0: ffff888029769728 (&pi_futex_key){....}-{2:2}, at: rt_mutex_cleanup_proxy_lock+0x23/0x100 kernel/locking/rtmutex_api.c:440
 #1: ffff8880312b65e8 (&p->pi_lock){-.-.}-{2:2}, at: remove_waiter+0x286/0xaf0 kernel/locking/rtmutex.c:1560
 #2: ffff8880b863a918 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0xad/0x140 kernel/sched/core.c:647

stack backtrace:
CPU: 1 UID: 0 PID: 12400 Comm: syz.3.1370 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_circular_bug+0x2e2/0x300 kernel/locking/lockdep.c:2043
 check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2175
 check_prev_add kernel/locking/lockdep.c:3165 [inline]
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x15a6/0x2cf0 kernel/locking/lockdep.c:5237
 lock_acquire+0x117/0x340 kernel/locking/lockdep.c:5868
 console_trylock_spinning kernel/printk/printk.c:2024 [inline]
 vprintk_emit+0x33d/0x5f0 kernel/printk/printk.c:2425
 _printk+0xcf/0x120 kernel/printk/printk.c:2451
 __report_bug+0x305/0x500 lib/bug.c:243
 report_bug+0x16a/0x220 lib/bug.c:281
 handle_bug+0x98/0x200 arch/x86/kernel/traps.c:435
 exc_invalid_op+0x1a/0x50 arch/x86/kernel/traps.c:489
 asm_exc_invalid_op+0x1a/0x20 arch/x86/include/asm/idtentry.h:616
RIP: 0010:sched_change_end+0x4f6/0x640 kernel/sched/core.c:10851
Code: 00 74 26 48 83 c4 38 5b 41 5c 41 5d 41 5e 41 5f 5d e9 be de cb 09 cc 90 0f 0b 90 e9 1d fc ff ff 90 0f 0b 90 e9 86 fc ff ff 90 <0f> 0b 90 eb d4 89 d9 80 e1 07 80 c1 03 38 c1 0f 8c 49 fb ff ff 48
RSP: 0018:ffffc9000e6af850 EFLAGS: 00010046
RAX: 1ffff11006256b70 RBX: ffffffff8d9a4810 RCX: ffffffff8192ed2f
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffff8880312b5b80
RBP: ffff8880312b5e28 R08: ffff8880312b5b87 R09: 1ffff11006256b70
R10: dffffc0000000000 R11: ffffed1006256b71 R12: dffffc0000000000
R13: ffff8880312b5b80 R14: ffff8880b863a900 R15: ffff8880312b5b80
 class_sched_change_destructor kernel/sched/sched.h:3956 [inline]
 rt_mutex_setprio+0x488/0xb70 kernel/sched/core.c:7331
 rt_mutex_adjust_prio kernel/locking/rtmutex.c:539 [inline]
 remove_waiter+0x7f5/0xaf0 kernel/locking/rtmutex.c:1567
 rt_mutex_cleanup_proxy_lock+0x6c/0x100 kernel/locking/rtmutex_api.c:458
 futex_wait_requeue_pi+0x481/0x850 kernel/futex/requeue.c:865
 do_futex+0x181/0x420 kernel/futex/syscalls.c:153
 __do_sys_futex kernel/futex/syscalls.c:207 [inline]
 __se_sys_futex+0x36f/0x400 kernel/futex/syscalls.c:188
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fdded78f749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fddee5af038 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: ffffffffffffffda RBX: 00007fdded9e5fa0 RCX: 00007fdded78f749
RDX: 0000000000000000 RSI: 000080000000000b RDI: 000020000000cffc
RBP: 00007fdded813f91 R08: 0000200000048000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fdded9e6038 R14: 00007fdded9e5fa0 R15: 00007ffc6c4ff6c8
 </TASK>
WARNING: kernel/sched/core.c:10852 at sched_change_end+0x4f6/0x640 kernel/sched/core.c:10851, CPU#1: syz.3.1370/12400
Modules linked in:
CPU: 1 UID: 0 PID: 12400 Comm: syz.3.1370 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:sched_change_end+0x4f6/0x640 kernel/sched/core.c:10851
Code: 00 74 26 48 83 c4 38 5b 41 5c 41 5d 41 5e 41 5f 5d e9 be de cb 09 cc 90 0f 0b 90 e9 1d fc ff ff 90 0f 0b 90 e9 86 fc ff ff 90 <0f> 0b 90 eb d4 89 d9 80 e1 07 80 c1 03 38 c1 0f 8c 49 fb ff ff 48
RSP: 0018:ffffc9000e6af850 EFLAGS: 00010046
RAX: 1ffff11006256b70 RBX: ffffffff8d9a4810 RCX: ffffffff8192ed2f
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffff8880312b5b80
RBP: ffff8880312b5e28 R08: ffff8880312b5b87 R09: 1ffff11006256b70
R10: dffffc0000000000 R11: ffffed1006256b71 R12: dffffc0000000000
R13: ffff8880312b5b80 R14: ffff8880b863a900 R15: ffff8880312b5b80
FS:  00007fddee5af6c0(0000) GS:ffff888125f32000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c43f3ae CR3: 0000000044bc2000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 class_sched_change_destructor kernel/sched/sched.h:3956 [inline]
 rt_mutex_setprio+0x488/0xb70 kernel/sched/core.c:7331
 rt_mutex_adjust_prio kernel/locking/rtmutex.c:539 [inline]
 remove_waiter+0x7f5/0xaf0 kernel/locking/rtmutex.c:1567
 rt_mutex_cleanup_proxy_lock+0x6c/0x100 kernel/locking/rtmutex_api.c:458
 futex_wait_requeue_pi+0x481/0x850 kernel/futex/requeue.c:865
 do_futex+0x181/0x420 kernel/futex/syscalls.c:153
 __do_sys_futex kernel/futex/syscalls.c:207 [inline]
 __se_sys_futex+0x36f/0x400 kernel/futex/syscalls.c:188
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fdded78f749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fddee5af038 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: ffffffffffffffda RBX: 00007fdded9e5fa0 RCX: 00007fdded78f749
RDX: 0000000000000000 RSI: 000080000000000b RDI: 000020000000cffc
RBP: 00007fdded813f91 R08: 0000200000048000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fdded9e6038 R14: 00007fdded9e5fa0 R15: 00007ffc6c4ff6c8
 </TASK>