------------[ cut here ]------------
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
migration/0/18 is trying to acquire lock:
ffffffff8d1260a0 (console_owner){-...}-{0:0}, at: rcu_try_lock_acquire include/linux/rcupdate.h:339 [inline]
ffffffff8d1260a0 (console_owner){-...}-{0:0}, at: srcu_read_lock_nmisafe include/linux/srcu.h:232 [inline]
ffffffff8d1260a0 (console_owner){-...}-{0:0}, at: console_srcu_read_lock kernel/printk/printk.c:292 [inline]
ffffffff8d1260a0 (console_owner){-...}-{0:0}, at: console_flush_all+0x10b/0xcf0 kernel/printk/printk.c:2992

but task is already holding lock:
ffff8880b8e3c298 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x9c/0x130 kernel/sched/core.c:567

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+0x29/0x130 kernel/sched/core.c:559
       raw_spin_rq_lock kernel/sched/sched.h:1379 [inline]
       rq_lock kernel/sched/sched.h:1688 [inline]
       task_fork_fair+0x62/0x1f0 kernel/sched/fair.c:12728
       sched_cgroup_fork+0x352/0x3e0 kernel/sched/core.c:4818
       copy_process+0x21fd/0x3da0 kernel/fork.c:2618
       kernel_clone+0x24b/0x8a0 kernel/fork.c:2918
       user_mode_thread+0x111/0x180 kernel/fork.c:2996
       rest_init+0x27/0x300 init/main.c:709
       arch_call_rest_init+0xe/0x10 init/main.c:840
       start_kernel+0x461/0x4e0 init/main.c:1085
       x86_64_start_reservations+0x2a/0x30 arch/x86/kernel/head64.c:555
       copy_bootdata+0x0/0xd0 arch/x86/kernel/head64.c:536
       secondary_startup_64_no_verify+0x179/0x17b

-> #3 (&p->pi_lock){-.-.}-{2:2}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0xb4/0x100 kernel/locking/spinlock.c:162
       class_raw_spinlock_irqsave_constructor include/linux/spinlock.h:523 [inline]
       try_to_wake_up+0x5b/0x10e0 kernel/sched/core.c:4233
       __wake_up_common+0x28e/0x4d0 kernel/sched/wait.c:107
       __wake_up_common_lock kernel/sched/wait.c:138 [inline]
       __wake_up+0x125/0x1a0 kernel/sched/wait.c:160
       tty_port_default_wakeup+0xa2/0xf0 drivers/tty/tty_port.c:69
       serial8250_tx_chars+0x6a2/0x8b0 drivers/tty/serial/8250/8250_port.c:1837
       serial8250_handle_irq+0x567/0x730 drivers/tty/serial/8250/8250_port.c:1944
       serial8250_default_handle_irq+0xb8/0x1a0 drivers/tty/serial/8250/8250_port.c:1964
       serial8250_interrupt+0x9f/0x1c0 drivers/tty/serial/8250/8250_core.c:127
       __handle_irq_event_percpu+0x271/0x940 kernel/irq/handle.c:158
       handle_irq_event_percpu kernel/irq/handle.c:193 [inline]
       handle_irq_event+0x8b/0x1e0 kernel/irq/handle.c:210
       handle_edge_irq+0x246/0xb20 kernel/irq/chip.c:831
       generic_handle_irq_desc include/linux/irqdesc.h:161 [inline]
       handle_irq arch/x86/kernel/irq.c:240 [inline]
       __common_interrupt+0x13b/0x230 arch/x86/kernel/irq.c:259
       common_interrupt+0xb4/0xd0 arch/x86/kernel/irq.c:249
       asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:678
       native_safe_halt arch/x86/include/asm/irqflags.h:48 [inline]
       pv_native_safe_halt+0xf/0x10 arch/x86/kernel/paravirt.c:147
       arch_safe_halt arch/x86/include/asm/paravirt.h:108 [inline]
       default_idle+0x13/0x20 arch/x86/kernel/process.c:753
       default_idle_call+0x6c/0xa0 kernel/sched/idle.c:97
       cpuidle_idle_call kernel/sched/idle.c:178 [inline]
       do_idle+0x334/0x5c0 kernel/sched/idle.c:302
       cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:401
       rest_init+0x2e2/0x300 init/main.c:744
       arch_call_rest_init+0xe/0x10 init/main.c:840
       start_kernel+0x461/0x4e0 init/main.c:1085
       x86_64_start_reservations+0x2a/0x30 arch/x86/kernel/head64.c:555
       copy_bootdata+0x0/0xd0 arch/x86/kernel/head64.c:536
       secondary_startup_64_no_verify+0x179/0x17b

-> #2 (&tty->write_wait){-...}-{2:2}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0xb4/0x100 kernel/locking/spinlock.c:162
       __wake_up_common_lock kernel/sched/wait.c:137 [inline]
       __wake_up+0x10b/0x1a0 kernel/sched/wait.c:160
       tty_port_default_wakeup+0xa2/0xf0 drivers/tty/tty_port.c:69
       serial8250_tx_chars+0x6a2/0x8b0 drivers/tty/serial/8250/8250_port.c:1837
       serial8250_handle_irq+0x567/0x730 drivers/tty/serial/8250/8250_port.c:1944
       serial8250_default_handle_irq+0xb8/0x1a0 drivers/tty/serial/8250/8250_port.c:1964
       serial8250_interrupt+0x9f/0x1c0 drivers/tty/serial/8250/8250_core.c:127
       __handle_irq_event_percpu+0x271/0x940 kernel/irq/handle.c:158
       handle_irq_event_percpu kernel/irq/handle.c:193 [inline]
       handle_irq_event+0x8b/0x1e0 kernel/irq/handle.c:210
       handle_edge_irq+0x246/0xb20 kernel/irq/chip.c:831
       generic_handle_irq_desc include/linux/irqdesc.h:161 [inline]
       handle_irq arch/x86/kernel/irq.c:240 [inline]
       __common_interrupt+0x13b/0x230 arch/x86/kernel/irq.c:259
       common_interrupt+0xb4/0xd0 arch/x86/kernel/irq.c:249
       asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:678
       native_safe_halt arch/x86/include/asm/irqflags.h:48 [inline]
       pv_native_safe_halt+0xf/0x10 arch/x86/kernel/paravirt.c:147
       arch_safe_halt arch/x86/include/asm/paravirt.h:108 [inline]
       default_idle+0x13/0x20 arch/x86/kernel/process.c:753
       default_idle_call+0x6c/0xa0 kernel/sched/idle.c:97
       cpuidle_idle_call kernel/sched/idle.c:178 [inline]
       do_idle+0x334/0x5c0 kernel/sched/idle.c:302
       cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:401
       rest_init+0x2e2/0x300 init/main.c:744
       arch_call_rest_init+0xe/0x10 init/main.c:840
       start_kernel+0x461/0x4e0 init/main.c:1085
       x86_64_start_reservations+0x2a/0x30 arch/x86/kernel/head64.c:555
       copy_bootdata+0x0/0xd0 arch/x86/kernel/head64.c:536
       secondary_startup_64_no_verify+0x179/0x17b

-> #1 (&port_lock_key){-.-.}-{2:2}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0xb4/0x100 kernel/locking/spinlock.c:162
       serial8250_console_write+0x181/0x18b0 drivers/tty/serial/8250/8250_port.c:3439
       console_emit_next_record kernel/printk/printk.c:2944 [inline]
       console_flush_all+0x6ad/0xcf0 kernel/printk/printk.c:3000
       console_unlock+0xad/0x350 kernel/printk/printk.c:3069
       vprintk_emit+0x497/0x610 kernel/printk/printk.c:2341
       _printk+0xde/0x130 kernel/printk/printk.c:2366
       register_console+0xb96/0xf00 kernel/printk/printk.c:3583
       univ8250_console_init+0x45/0x50 drivers/tty/serial/8250/8250_core.c:717
       console_init+0x17b/0x5d0 kernel/printk/printk.c:3726
       start_kernel+0x2c8/0x4e0 init/main.c:1021
       x86_64_start_reservations+0x2a/0x30 arch/x86/kernel/head64.c:555
       copy_bootdata+0x0/0xd0 arch/x86/kernel/head64.c:536
       secondary_startup_64_no_verify+0x179/0x17b

-> #0 (console_owner){-...}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3134 [inline]
       check_prevs_add kernel/locking/lockdep.c:3253 [inline]
       validate_chain kernel/locking/lockdep.c:3869 [inline]
       __lock_acquire+0x37ef/0x7d80 kernel/locking/lockdep.c:5137
       lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5754
       console_lock_spinning_enable kernel/printk/printk.c:1871 [inline]
       console_emit_next_record kernel/printk/printk.c:2938 [inline]
       console_flush_all+0x676/0xcf0 kernel/printk/printk.c:3000
       console_unlock+0xad/0x350 kernel/printk/printk.c:3069
       vprintk_emit+0x497/0x610 kernel/printk/printk.c:2341
       _printk+0xde/0x130 kernel/printk/printk.c:2366
       __report_bug lib/bug.c:195 [inline]
       report_bug+0x34e/0x4f0 lib/bug.c:219
       handle_bug+0xcf/0x120 arch/x86/kernel/traps.c:310
       exc_invalid_op+0x1a/0x50 arch/x86/kernel/traps.c:345
       asm_exc_invalid_op+0x1a/0x20 arch/x86/include/asm/idtentry.h:606
       update_rq_clock+0x32e/0x4b0 kernel/sched/core.c:772
       pick_next_task kernel/sched/core.c:6187 [inline]
       __schedule+0x2c72/0x4660 kernel/sched/core.c:6663
       schedule+0xbd/0x170 kernel/sched/core.c:6775
       smpboot_thread_fn+0x71c/0x9f0 kernel/smpboot.c:160
       kthread+0x2fa/0x390 kernel/kthread.c:388
       ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
       ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293

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 migration/0/18:
 #0: ffff8880b8e3c298 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x9c/0x130 kernel/sched/core.c:567
 #1: ffffffff8d126180 (console_lock){+.+.}-{0:0}, at: _printk+0xde/0x130 kernel/printk/printk.c:2366
 #2: ffffffff8d00d990 (console_srcu){....}-{0:0}, at: rcu_try_lock_acquire include/linux/rcupdate.h:339 [inline]
 #2: ffffffff8d00d990 (console_srcu){....}-{0:0}, at: srcu_read_lock_nmisafe include/linux/srcu.h:232 [inline]
 #2: ffffffff8d00d990 (console_srcu){....}-{0:0}, at: console_srcu_read_lock kernel/printk/printk.c:292 [inline]
 #2: ffffffff8d00d990 (console_srcu){....}-{0:0}, at: console_flush_all+0x10b/0xcf0 kernel/printk/printk.c:2992

stack backtrace:
CPU: 0 PID: 18 Comm: migration/0 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Stopper: 0x0 <- 0x0
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 check_noncircular+0x2fc/0x400 kernel/locking/lockdep.c:2187
 check_prev_add kernel/locking/lockdep.c:3134 [inline]
 check_prevs_add kernel/locking/lockdep.c:3253 [inline]
 validate_chain kernel/locking/lockdep.c:3869 [inline]
 __lock_acquire+0x37ef/0x7d80 kernel/locking/lockdep.c:5137
 lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5754
 console_lock_spinning_enable kernel/printk/printk.c:1871 [inline]
 console_emit_next_record kernel/printk/printk.c:2938 [inline]
 console_flush_all+0x676/0xcf0 kernel/printk/printk.c:3000
 console_unlock+0xad/0x350 kernel/printk/printk.c:3069
 vprintk_emit+0x497/0x610 kernel/printk/printk.c:2341
 _printk+0xde/0x130 kernel/printk/printk.c:2366
 __report_bug lib/bug.c:195 [inline]
 report_bug+0x34e/0x4f0 lib/bug.c:219
 handle_bug+0xcf/0x120 arch/x86/kernel/traps.c:310
 exc_invalid_op+0x1a/0x50 arch/x86/kernel/traps.c:345
 asm_exc_invalid_op+0x1a/0x20 arch/x86/include/asm/idtentry.h:606
RIP: 0010:lockdep_assert_rq_held kernel/sched/sched.h:1370 [inline]
RIP: 0010:update_rq_clock+0x32e/0x4b0 kernel/sched/core.c:756
Code: 00 00 48 89 d8 48 c1 e8 03 42 80 3c 28 00 74 08 48 89 df e8 24 f8 82 00 48 01 2b 48 83 c4 08 5b 41 5c 41 5d 41 5e 41 5f 5d c3 <0f> 0b e9 62 fd ff ff 48 89 df 48 83 c4 08 5b 41 5c 41 5d 41 5e 41
RSP: 0000:ffffc90000177bc0 EFLAGS: 00010046
RAX: 0000000000000000 RBX: ffff8880b8f3c280 RCX: 84075e1f671ed700
RDX: 0000000000000003 RSI: ffffffff8acadd60 RDI: ffffffff8b1d0660
RBP: ffffc90000177e18 R08: ffffffff8e8c7caf R09: 1ffffffff1d18f95
R10: dffffc0000000000 R11: fffffbfff1d18f96 R12: ffffffff8ca92a38
R13: dffffc0000000000 R14: ffff8880b8f3cfc8 R15: ffff8880b8f3c280
 pick_next_task kernel/sched/core.c:6187 [inline]
 __schedule+0x2c72/0x4660 kernel/sched/core.c:6663
 schedule+0xbd/0x170 kernel/sched/core.c:6775
 smpboot_thread_fn+0x71c/0x9f0 kernel/smpboot.c:160
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
WARNING: CPU: 0 PID: 18 at kernel/sched/sched.h:1370 update_rq_clock+0x32e/0x4b0 kernel/sched/core.c:772
Modules linked in:
CPU: 0 PID: 18 Comm: migration/0 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Stopper: 0x0 <- 0x0
RIP: 0010:lockdep_assert_rq_held kernel/sched/sched.h:1370 [inline]
RIP: 0010:update_rq_clock+0x32e/0x4b0 kernel/sched/core.c:756
Code: 00 00 48 89 d8 48 c1 e8 03 42 80 3c 28 00 74 08 48 89 df e8 24 f8 82 00 48 01 2b 48 83 c4 08 5b 41 5c 41 5d 41 5e 41 5f 5d c3 <0f> 0b e9 62 fd ff ff 48 89 df 48 83 c4 08 5b 41 5c 41 5d 41 5e 41
RSP: 0000:ffffc90000177bc0 EFLAGS: 00010046
RAX: 0000000000000000 RBX: ffff8880b8f3c280 RCX: 84075e1f671ed700
RDX: 0000000000000003 RSI: ffffffff8acadd60 RDI: ffffffff8b1d0660
RBP: ffffc90000177e18 R08: ffffffff8e8c7caf R09: 1ffffffff1d18f95
R10: dffffc0000000000 R11: fffffbfff1d18f96 R12: ffffffff8ca92a38
R13: dffffc0000000000 R14: ffff8880b8f3cfc8 R15: ffff8880b8f3c280
FS:  0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c33ee44 CR3: 000000004ca68000 CR4: 00000000003506f0
Call Trace:
 <TASK>
 pick_next_task kernel/sched/core.c:6187 [inline]
 __schedule+0x2c72/0x4660 kernel/sched/core.c:6663
 schedule+0xbd/0x170 kernel/sched/core.c:6775
 smpboot_thread_fn+0x71c/0x9f0 kernel/smpboot.c:160
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>