------------[ cut here ]------------
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.0.17/5992 is trying to acquire lock:
ffffffff8e133180 (console_owner){....}-{0:0}, at: rcu_try_lock_acquire include/linux/rcupdate.h:336 [inline]
ffffffff8e133180 (console_owner){....}-{0:0}, at: srcu_read_lock_nmisafe include/linux/srcu.h:409 [inline]
ffffffff8e133180 (console_owner){....}-{0:0}, at: console_srcu_read_lock kernel/printk/printk.c:289 [inline]
ffffffff8e133180 (console_owner){....}-{0:0}, at: console_flush_one_record kernel/printk/printk.c:3192 [inline]
ffffffff8e133180 (console_owner){....}-{0:0}, at: console_flush_all+0x131/0xb60 kernel/printk/printk.c:3289

but task is already holding lock:
ffff8880b873ab18 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x2a/0x140 kernel/sched/core.c:639

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:2469
       kernel_clone+0x21e/0x820 kernel/fork.c:2655
       user_mode_thread+0xdd/0x140 kernel/fork.c:2731
       rest_init+0x23/0x300 init/main.c:723
       start_kernel+0x3ac/0x400 init/main.c:1208
       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:209
       handle_irq_event_percpu kernel/irq/handle.c:246 [inline]
       handle_irq_event+0x8b/0x1e0 kernel/irq/handle.c:263
       handle_edge_irq+0x23b/0xa10 kernel/irq/chip.c:855
       generic_handle_irq_desc include/linux/irqdesc.h:186 [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
       get_page_from_freelist+0x446/0x2440 mm/page_alloc.c:3841
       alloc_frozen_pages_nolock_noprof+0xac/0x150 mm/page_alloc.c:7654
       alloc_slab_page mm/slub.c:3072 [inline]
       allocate_slab+0xf4/0x3b0 mm/slub.c:3248
       new_slab mm/slub.c:3302 [inline]
       ___slab_alloc+0xf2b/0x1960 mm/slub.c:4656
       __slab_alloc+0x65/0x100 mm/slub.c:4779
       __slab_alloc_node mm/slub.c:4855 [inline]
       slab_alloc_node mm/slub.c:5255 [inline]
       kmem_cache_alloc_noprof+0x40f/0x710 mm/slub.c:5274
       kmem_alloc_batch lib/debugobjects.c:371 [inline]
       fill_pool+0x100/0x570 lib/debugobjects.c:403
       debug_objects_fill_pool lib/debugobjects.c:725 [inline]
       debug_object_activate+0x498/0x540 lib/debugobjects.c:814
       debug_rcu_head_queue kernel/rcu/rcu.h:236 [inline]
       __call_rcu_common kernel/rcu/tree.c:3104 [inline]
       call_rcu+0xaa/0x9c0 kernel/rcu/tree.c:3239
       slab_free_hook mm/slub.c:2504 [inline]
       slab_free mm/slub.c:6674 [inline]
       kmem_cache_free+0x488/0x620 mm/slub.c:6785
       exit_mmap+0x52c/0xb10 mm/mmap.c:1302
       __mmput+0x118/0x430 kernel/fork.c:1177
       exit_mm+0x1da/0x2c0 kernel/exit.c:581
       do_exit+0x850/0x25b0 kernel/exit.c:959
       do_group_exit+0x21c/0x2d0 kernel/exit.c:1112
       __do_sys_exit_group kernel/exit.c:1123 [inline]
       __se_sys_exit_group kernel/exit.c:1121 [inline]
       __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1121
       __pfx_syscall_get_nr+0x0/0x10 arch/x86/include/generated/asm/syscalls_64.h:232
       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:209
       handle_irq_event_percpu kernel/irq/handle.c:246 [inline]
       handle_irq_event+0x8b/0x1e0 kernel/irq/handle.c:263
       handle_edge_irq+0x23b/0xa10 kernel/irq/chip.c:855
       generic_handle_irq_desc include/linux/irqdesc.h:186 [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+0x252/0x400 init/main.c:1145
       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_lock_spinning_enable kernel/printk/printk.c:1900 [inline]
       console_emit_next_record kernel/printk/printk.c:3123 [inline]
       console_flush_one_record kernel/printk/printk.c:3215 [inline]
       console_flush_all+0x6ee/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
       __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]
       __sched_setscheduler+0x1538/0x1ab0 kernel/sched/syscalls.c:680
       _sched_setscheduler kernel/sched/syscalls.c:742 [inline]
       sched_setscheduler kernel/sched/syscalls.c:759 [inline]
       do_sched_setscheduler+0x19b/0x270 kernel/sched/syscalls.c:864
       __do_sys_sched_setscheduler kernel/sched/syscalls.c:937 [inline]
       __se_sys_sched_setscheduler kernel/sched/syscalls.c:932 [inline]
       __x64_sys_sched_setscheduler+0x79/0x90 kernel/sched/syscalls.c:932
       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 ***

4 locks held by syz.0.17/5992:
 #0: ffff88802f67e5e8 (&p->pi_lock){-.-.}-{2:2}, at: task_rq_lock+0x5b/0x470 kernel/sched/core.c:737
 #1: ffff8880b873ab18 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x2a/0x140 kernel/sched/core.c:639
 #2: ffffffff8e1331e0 (console_lock){+.+.}-{0:0}, at: _printk+0xcf/0x120 kernel/printk/printk.c:2451
 #3: ffffffff8e01aa98 (console_srcu){....}-{0:0}, at: rcu_try_lock_acquire include/linux/rcupdate.h:336 [inline]
 #3: ffffffff8e01aa98 (console_srcu){....}-{0:0}, at: srcu_read_lock_nmisafe include/linux/srcu.h:409 [inline]
 #3: ffffffff8e01aa98 (console_srcu){....}-{0:0}, at: console_srcu_read_lock kernel/printk/printk.c:289 [inline]
 #3: ffffffff8e01aa98 (console_srcu){....}-{0:0}, at: console_flush_one_record kernel/printk/printk.c:3192 [inline]
 #3: ffffffff8e01aa98 (console_srcu){....}-{0:0}, at: console_flush_all+0x131/0xb60 kernel/printk/printk.c:3289

stack backtrace:
CPU: 0 UID: 0 PID: 5992 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
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_lock_spinning_enable kernel/printk/printk.c:1900 [inline]
 console_emit_next_record kernel/printk/printk.c:3123 [inline]
 console_flush_one_record kernel/printk/printk.c:3215 [inline]
 console_flush_all+0x6ee/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
 __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 c3 cc cc cc cc 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:ffffc90002f47b90 EFLAGS: 00010046
RAX: 1ffff11005ecfb70 RBX: ffffffff8dba8ed0 RCX: ffffffff8192e20f
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffff88802f67db80
RBP: ffff88802f67de28 R08: ffff88802f67db87 R09: 1ffff11005ecfb70
R10: dffffc0000000000 R11: ffffed1005ecfb71 R12: dffffc0000000000
R13: ffff88802f67db80 R14: ffff8880b873ab00 R15: ffff88802f67db80
 class_sched_change_destructor kernel/sched/sched.h:3956 [inline]
 __sched_setscheduler+0x1538/0x1ab0 kernel/sched/syscalls.c:680
 _sched_setscheduler kernel/sched/syscalls.c:742 [inline]
 sched_setscheduler kernel/sched/syscalls.c:759 [inline]
 do_sched_setscheduler+0x19b/0x270 kernel/sched/syscalls.c:864
 __do_sys_sched_setscheduler kernel/sched/syscalls.c:937 [inline]
 __se_sys_sched_setscheduler kernel/sched/syscalls.c:932 [inline]
 __x64_sys_sched_setscheduler+0x79/0x90 kernel/sched/syscalls.c:932
 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: 0033:0x7fdbc5f8f749
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:00007fdbc6e8d038 EFLAGS: 00000246 ORIG_RAX: 0000000000000090
RAX: ffffffffffffffda RBX: 00007fdbc61e6090 RCX: 00007fdbc5f8f749
RDX: 0000200000000240 RSI: 0000000000000005 RDI: 0000000000000003
RBP: 00007fdbc6013f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fdbc61e6128 R14: 00007fdbc61e6090 R15: 00007fff5eb16038
 </TASK>
WARNING: kernel/sched/core.c:10852 at sched_change_end+0x4f6/0x640 kernel/sched/core.c:10851, CPU#0: syz.0.17/5992
Modules linked in:
CPU: 0 UID: 0 PID: 5992 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
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 c3 cc cc cc cc 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:ffffc90002f47b90 EFLAGS: 00010046
RAX: 1ffff11005ecfb70 RBX: ffffffff8dba8ed0 RCX: ffffffff8192e20f
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffff88802f67db80
RBP: ffff88802f67de28 R08: ffff88802f67db87 R09: 1ffff11005ecfb70
R10: dffffc0000000000 R11: ffffed1005ecfb71 R12: dffffc0000000000
R13: ffff88802f67db80 R14: ffff8880b873ab00 R15: ffff88802f67db80
FS:  00007fdbc6e8d6c0(0000) GS:ffff888125c25000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000240 CR3: 00000000742a0000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 class_sched_change_destructor kernel/sched/sched.h:3956 [inline]
 __sched_setscheduler+0x1538/0x1ab0 kernel/sched/syscalls.c:680
 _sched_setscheduler kernel/sched/syscalls.c:742 [inline]
 sched_setscheduler kernel/sched/syscalls.c:759 [inline]
 do_sched_setscheduler+0x19b/0x270 kernel/sched/syscalls.c:864
 __do_sys_sched_setscheduler kernel/sched/syscalls.c:937 [inline]
 __se_sys_sched_setscheduler kernel/sched/syscalls.c:932 [inline]
 __x64_sys_sched_setscheduler+0x79/0x90 kernel/sched/syscalls.c:932
 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: 0033:0x7fdbc5f8f749
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:00007fdbc6e8d038 EFLAGS: 00000246 ORIG_RAX: 0000000000000090
RAX: ffffffffffffffda RBX: 00007fdbc61e6090 RCX: 00007fdbc5f8f749
RDX: 0000200000000240 RSI: 0000000000000005 RDI: 0000000000000003
RBP: 00007fdbc6013f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fdbc61e6128 R14: 00007fdbc61e6090 R15: 00007fff5eb16038
 </TASK>