syzbot

------------[ cut here ]------------
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
migration/0/19 is trying to acquire lock:
ffffffff8e6f3600 (console_owner){....}-{0:0}, at: console_lock_spinning_enable+0x61/0x80 kernel/printk/printk.c:1902

but task is already holding lock:
ffff8880b843b2e0 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested kernel/sched/core.c:655 [inline]
ffff8880b843b2e0 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x88/0x140 kernel/sched/core.c:639

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #5 (&rq->__lock){-.-.}-{2:2}:
       _raw_spin_lock_nested+0x31/0x40 kernel/locking/spinlock.c:378
       raw_spin_rq_lock_nested+0x2c/0x140 kernel/sched/core.c:647
       raw_spin_rq_lock kernel/sched/sched.h:1615 [inline]
       _task_rq_lock+0xcf/0x490 kernel/sched/core.c:747
       cgroup_move_task+0x81/0x2b0 kernel/sched/psi.c:1170
       css_set_move_task+0x285/0x600 kernel/cgroup/cgroup.c:948
       cgroup_post_fork+0x202/0x9b0 kernel/cgroup/cgroup.c:6911
       copy_process+0x5f26/0x7a10 kernel/fork.c:2467
       kernel_clone+0xfc/0x9a0 kernel/fork.c:2654
       user_mode_thread+0xcc/0x110 kernel/fork.c:2730
       rest_init+0x21/0x260 init/main.c:725
       start_kernel+0x47f/0x480 init/main.c:1210
       x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310
       x86_64_start_kernel+0x12b/0x130 arch/x86/kernel/head64.c:291
       common_startup_64+0x13e/0x148

-> #4 (&p->pi_lock){-.-.}-{2:2}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:132 [inline]
       _raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:162
       class_raw_spinlock_irqsave_constructor include/linux/spinlock.h:570 [inline]
       try_to_wake_up+0xb2/0x1a80 kernel/sched/core.c:4130
       create_worker+0x33a/0x740 kernel/workqueue.c:2847
       workqueue_init+0x768/0x930 kernel/workqueue.c:8042
       kernel_init_freeable+0x3d4/0x7a0 init/main.c:1677
       kernel_init+0x1f/0x1e0 init/main.c:1582
       ret_from_fork+0x754/0xd80 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #3 (&pool->lock){-.-.}-{2:2}:
       __raw_spin_lock include/linux/spinlock_api_smp.h:158 [inline]
       _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
       __queue_work+0x270/0x1150 kernel/workqueue.c:2314
       queue_work_on+0x1a9/0x1e0 kernel/workqueue.c:2405
       queue_work include/linux/workqueue.h:669 [inline]
       rpm_suspend+0xee1/0x11c0 drivers/base/power/runtime.c:688
       rpm_idle+0x637/0x7c0 drivers/base/power/runtime.c:562
       __pm_runtime_idle+0xba/0x1a0 drivers/base/power/runtime.c:1129
       pm_runtime_put include/linux/pm_runtime.h:551 [inline]
       __device_attach+0x37e/0x4d0 drivers/base/dd.c:1051
       device_initial_probe+0xaf/0xd0 drivers/base/dd.c:1088
       bus_probe_device+0x64/0x160 drivers/base/bus.c:574
       device_add+0x11d9/0x1950 drivers/base/core.c:3689
       serial_base_port_add+0x227/0x2b0 drivers/tty/serial/serial_base_bus.c:186
       serial_core_port_device_add drivers/tty/serial/serial_core.c:3257 [inline]
       serial_core_register_port+0x13c/0x17a0 drivers/tty/serial/serial_core.c:3296
       serial8250_register_8250_port+0x155a/0x2260 drivers/tty/serial/8250/8250_core.c:822
       serial_pnp_probe+0x436/0x930 drivers/tty/serial/8250/8250_pnp.c:480
       pnp_device_probe+0x2b3/0x4a0 drivers/pnp/driver.c:111
       call_driver_probe drivers/base/dd.c:583 [inline]
       really_probe+0x241/0xa60 drivers/base/dd.c:661
       __driver_probe_device+0x1de/0x400 drivers/base/dd.c:803
       driver_probe_device+0x4c/0x1b0 drivers/base/dd.c:833
       __driver_attach+0x217/0x5c0 drivers/base/dd.c:1227
       bus_for_each_dev+0x13e/0x1d0 drivers/base/bus.c:383
       bus_add_driver+0x305/0x5b0 drivers/base/bus.c:715
       driver_register+0x1e2/0x360 drivers/base/driver.c:249
       serial8250_init+0xcc/0x1b0 drivers/tty/serial/8250/8250_platform.c:317
       do_one_initcall+0x11d/0x760 init/main.c:1382
       do_initcall_level init/main.c:1444 [inline]
       do_initcalls init/main.c:1460 [inline]
       do_basic_setup init/main.c:1479 [inline]
       kernel_init_freeable+0x6e5/0x7a0 init/main.c:1692
       kernel_init+0x1f/0x1e0 init/main.c:1582
       ret_from_fork+0x754/0xd80 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #2 (&dev->power.lock){-.-.}-{3:3}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:132 [inline]
       _raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:162
       __pm_runtime_resume+0xa9/0x170 drivers/base/power/runtime.c:1196
       pm_runtime_get include/linux/pm_runtime.h:494 [inline]
       __uart_start+0x1b0/0x510 drivers/tty/serial/serial_core.c:149
       uart_write+0x211/0xb20 drivers/tty/serial/serial_core.c:633
       process_output_block drivers/tty/n_tty.c:557 [inline]
       n_tty_write+0x44f/0x12d0 drivers/tty/n_tty.c:2366
       iterate_tty_write drivers/tty/tty_io.c:1006 [inline]
       file_tty_write.isra.0+0x4d2/0x890 drivers/tty/tty_io.c:1081
       tty_write drivers/tty/tty_io.c:1102 [inline]
       redirected_tty_write drivers/tty/tty_io.c:1125 [inline]
       redirected_tty_write+0xd4/0x120 drivers/tty/tty_io.c:1105
       new_sync_write fs/read_write.c:595 [inline]
       vfs_write+0x6ac/0x1070 fs/read_write.c:688
       ksys_write+0x12a/0x250 fs/read_write.c:740
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x106/0xf80 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:132 [inline]
       _raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:162
       uart_port_lock_irqsave include/linux/serial_core.h:717 [inline]
       serial8250_console_write+0x17e/0x1900 drivers/tty/serial/8250/8250_port.c:3301
       console_emit_next_record kernel/printk/printk.c:3183 [inline]
       console_flush_one_record+0x790/0xe50 kernel/printk/printk.c:3269
       console_flush_all kernel/printk/printk.c:3343 [inline]
       __console_flush_and_unlock kernel/printk/printk.c:3373 [inline]
       console_unlock+0x103/0x260 kernel/printk/printk.c:3413
       vprintk_emit+0x407/0x6b0 kernel/printk/printk.c:2479
       _printk+0xcf/0x110 kernel/printk/printk.c:2504
       register_console.cold+0xc0/0x248 kernel/printk/printk.c:4208
       univ8250_console_init+0x6f/0x80 drivers/tty/serial/8250/8250_core.c:515
       console_init+0x423/0x620 kernel/printk/printk.c:4407
       start_kernel+0x305/0x480 init/main.c:1147
       x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310
       x86_64_start_kernel+0x12b/0x130 arch/x86/kernel/head64.c:291
       common_startup_64+0x13e/0x148

-> #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+0x14b8/0x2630 kernel/locking/lockdep.c:5237
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1cf/0x380 kernel/locking/lockdep.c:5825
       console_lock_spinning_enable+0x72/0x80 kernel/printk/printk.c:1902
       console_emit_next_record kernel/printk/printk.c:3177 [inline]
       console_flush_one_record+0x739/0xe50 kernel/printk/printk.c:3269
       console_flush_all kernel/printk/printk.c:3343 [inline]
       __console_flush_and_unlock kernel/printk/printk.c:3373 [inline]
       console_unlock+0x103/0x260 kernel/printk/printk.c:3413
       vprintk_emit+0x407/0x6b0 kernel/printk/printk.c:2479
       _printk+0xcf/0x110 kernel/printk/printk.c:2504
       __report_bug.cold+0x15/0x137 lib/bug.c:243
       report_bug+0xb2/0x220 lib/bug.c:281
       handle_bug+0x16a/0x2a0 arch/x86/kernel/traps.c:435
       exc_invalid_op+0x17/0x50 arch/x86/kernel/traps.c:489
       asm_exc_invalid_op+0x1a/0x20 arch/x86/include/asm/idtentry.h:616
       lockdep_assert_rq_held kernel/sched/sched.h:1600 [inline]
       lockdep_assert_rq_held kernel/sched/sched.h:1597 [inline]
       update_rq_clock+0x40a/0xd20 kernel/sched/core.c:850
       pick_next_task kernel/sched/core.c:6129 [inline]
       __schedule+0x1b7d/0x6120 kernel/sched/core.c:6849
       __schedule_loop kernel/sched/core.c:6990 [inline]
       schedule+0xdd/0x390 kernel/sched/core.c:7005
       smpboot_thread_fn+0x893/0xaa0 kernel/smpboot.c:156
       kthread+0x370/0x450 kernel/kthread.c:436
       ret_from_fork+0x754/0xd80 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

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/0/19:
 #0: ffff8880b843b2e0 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested kernel/sched/core.c:655 [inline]
 #0: ffff8880b843b2e0 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x88/0x140 kernel/sched/core.c:639
 #1: ffffffff8e7d3a40 (console_lock){+.+.}-{0:0}, at: _printk+0xcf/0x110 kernel/printk/printk.c:2504
 #2: ffffffff8e7d3ab8 (console_srcu){....}-{0:0}, at: rcu_try_lock_acquire include/linux/rcupdate.h:317 [inline]
 #2: ffffffff8e7d3ab8 (console_srcu){....}-{0:0}, at: srcu_read_lock_nmisafe include/linux/srcu.h:428 [inline]
 #2: ffffffff8e7d3ab8 (console_srcu){....}-{0:0}, at: console_srcu_read_lock kernel/printk/printk.c:291 [inline]
 #2: ffffffff8e7d3ab8 (console_srcu){....}-{0:0}, at: console_flush_one_record+0xfd/0xe50 kernel/printk/printk.c:3246

stack backtrace:
CPU: 0 UID: 0 PID: 19 Comm: migration/0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/27/2026
Stopper: 0x0 <- 0x0
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_circular_bug.cold+0x178/0x1c7 kernel/locking/lockdep.c:2043
 check_noncircular+0x146/0x160 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+0x14b8/0x2630 kernel/locking/lockdep.c:5237
 lock_acquire kernel/locking/lockdep.c:5868 [inline]
 lock_acquire+0x1cf/0x380 kernel/locking/lockdep.c:5825
 console_lock_spinning_enable+0x72/0x80 kernel/printk/printk.c:1902
 console_emit_next_record kernel/printk/printk.c:3177 [inline]
 console_flush_one_record+0x739/0xe50 kernel/printk/printk.c:3269
 console_flush_all kernel/printk/printk.c:3343 [inline]
 __console_flush_and_unlock kernel/printk/printk.c:3373 [inline]
 console_unlock+0x103/0x260 kernel/printk/printk.c:3413
 vprintk_emit+0x407/0x6b0 kernel/printk/printk.c:2479
 _printk+0xcf/0x110 kernel/printk/printk.c:2504
 __report_bug.cold+0x15/0x137 lib/bug.c:243
 report_bug+0xb2/0x220 lib/bug.c:281
 handle_bug+0x16a/0x2a0 arch/x86/kernel/traps.c:435
 exc_invalid_op+0x17/0x50 arch/x86/kernel/traps.c:489
 asm_exc_invalid_op+0x1a/0x20 arch/x86/include/asm/idtentry.h:616
RIP: 0010:lockdep_assert_rq_held kernel/sched/sched.h:1600 [inline]
RIP: 0010:lockdep_assert_rq_held kernel/sched/sched.h:1597 [inline]
RIP: 0010:update_rq_clock+0x40a/0xd20 kernel/sched/core.c:850
Code: ab 48 0b 00 00 48 83 c4 18 5b 5d 41 5c 41 5d 41 5e 41 5f e9 58 4b ba 09 a8 04 0f 84 df fc ff ff 90 0f 0b 90 e9 d6 fc ff ff 90 <0f> 0b 90 e9 92 fc ff ff 4c 8d 83 40 0b 00 00 48 b8 00 00 00 00 00
RSP: 0018:ffffc90000187c28 EFLAGS: 00010046
RAX: 0000000000000000 RBX: ffff8880b853b280 RCX: 0000000000000001
RDX: 0000000000000046 RSI: ffffffff8de57649 RDI: ffffffff8c1af9a0
RBP: ffffc90000187dd0 R08: 0000000000000001 R09: 0000000000000001
R10: ffff8880798af007 R11: 00000017ae826000 R12: ffffffff90d9e1e4
R13: ffff8880b853c0c0 R14: ffff888020b60000 R15: ffff8880b853b280
 pick_next_task kernel/sched/core.c:6129 [inline]
 __schedule+0x1b7d/0x6120 kernel/sched/core.c:6849
 __schedule_loop kernel/sched/core.c:6990 [inline]
 schedule+0xdd/0x390 kernel/sched/core.c:7005
 smpboot_thread_fn+0x893/0xaa0 kernel/smpboot.c:156
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x754/0xd80 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
debug_locks && !(lock_is_held(&(__rq_lockp(rq))->dep_map) != 0)
WARNING: kernel/sched/sched.h:1600 at lockdep_assert_rq_held kernel/sched/sched.h:1600 [inline], CPU#0: migration/0/19
WARNING: kernel/sched/sched.h:1600 at lockdep_assert_rq_held kernel/sched/sched.h:1597 [inline], CPU#0: migration/0/19
WARNING: kernel/sched/sched.h:1600 at update_rq_clock+0x40a/0xd20 kernel/sched/core.c:850, CPU#0: migration/0/19
Modules linked in:
CPU: 0 UID: 0 PID: 19 Comm: migration/0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/27/2026
Stopper: 0x0 <- 0x0
RIP: 0010:lockdep_assert_rq_held kernel/sched/sched.h:1600 [inline]
RIP: 0010:lockdep_assert_rq_held kernel/sched/sched.h:1597 [inline]
RIP: 0010:update_rq_clock+0x40a/0xd20 kernel/sched/core.c:850
Code: ab 48 0b 00 00 48 83 c4 18 5b 5d 41 5c 41 5d 41 5e 41 5f e9 58 4b ba 09 a8 04 0f 84 df fc ff ff 90 0f 0b 90 e9 d6 fc ff ff 90 <0f> 0b 90 e9 92 fc ff ff 4c 8d 83 40 0b 00 00 48 b8 00 00 00 00 00
RSP: 0018:ffffc90000187c28 EFLAGS: 00010046
RAX: 0000000000000000 RBX: ffff8880b853b280 RCX: 0000000000000001
RDX: 0000000000000046 RSI: ffffffff8de57649 RDI: ffffffff8c1af9a0
RBP: ffffc90000187dd0 R08: 0000000000000001 R09: 0000000000000001
R10: ffff8880798af007 R11: 00000017ae826000 R12: ffffffff90d9e1e4
R13: ffff8880b853c0c0 R14: ffff888020b60000 R15: ffff8880b853b280
FS:  0000000000000000(0000) GS:ffff88812434d000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055558c2ad9e8 CR3: 0000000072618000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 pick_next_task kernel/sched/core.c:6129 [inline]
 __schedule+0x1b7d/0x6120 kernel/sched/core.c:6849
 __schedule_loop kernel/sched/core.c:6990 [inline]
 schedule+0xdd/0x390 kernel/sched/core.c:7005
 smpboot_thread_fn+0x893/0xaa0 kernel/smpboot.c:156
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x754/0xd80 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>