syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-...!: (1 GPs behind) idle=95d4/1/0x4000000000000000 softirq=22269/22270 fqs=0
rcu: 	(detected by 1, t=10506 jiffies, g=19481, q=214 ncpus=2)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 12 Comm: kworker/u8:1 Not tainted 6.12.0-syzkaller-09567-g7eef7e306d3c #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Workqueue: events_unbound flush_to_ldisc
RIP: 0010:__lock_acquire+0x3c3/0x3c40 kernel/locking/lockdep.c:5163
Code: c1 e2 12 81 e2 00 00 04 00 09 c8 c1 e3 13 09 d0 8b 94 24 48 01 00 00 09 d8 c1 e2 14 09 d0 8b 94 24 38 01 00 00 c1 e2 15 09 d0 <41> 8b 57 20 81 e2 ff 1f 00 00 09 d0 48 89 fa 41 89 47 20 48 c1 ea
RSP: 0018:ffffc90000007b38 EFLAGS: 00000006
RAX: 00000000000c4000 RBX: 0000000000080000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff88801c6b5344 RDI: ffff88801c6b5474
RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000001
R10: 000000000000001e R11: 0000000000000007 R12: 0000000000000002
R13: ffff88801c6b4880 R14: 0000000000000b23 R15: ffff88801c6b5450
FS:  0000000000000000(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b30418ff8 CR3: 0000000035260000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <NMI>
 </NMI>
 <IRQ>
 lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5849
 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
 _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
 spin_lock include/linux/spinlock.h:351 [inline]
 advance_sched+0xd8/0xc60 net/sched/sch_taprio.c:924
 __run_hrtimer kernel/time/hrtimer.c:1739 [inline]
 __hrtimer_run_queues+0x20a/0xae0 kernel/time/hrtimer.c:1803
 hrtimer_interrupt+0x392/0x8e0 kernel/time/hrtimer.c:1865
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1038 [inline]
 __sysvec_apic_timer_interrupt+0x10f/0x400 arch/x86/kernel/apic/apic.c:1055
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1049 [inline]
 sysvec_apic_timer_interrupt+0x9f/0xc0 arch/x86/kernel/apic/apic.c:1049
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0x31/0x80 kernel/locking/spinlock.c:194
Code: f5 53 48 8b 74 24 10 48 89 fb 48 83 c7 18 e8 66 1b 3a f6 48 89 df e8 ce 9a 3a f6 f7 c5 00 02 00 00 75 23 9c 58 f6 c4 02 75 37 <bf> 01 00 00 00 e8 55 90 2b f6 65 8b 05 86 8b d2 74 85 c0 74 16 5b
RSP: 0018:ffffc90000117770 EFLAGS: 00000246
RAX: 0000000000000002 RBX: ffff888024efb940 RCX: 1ffffffff2dd9427
RDX: 0000000000000000 RSI: ffffffff8b6cdee0 RDI: ffffffff8bd1d600
RBP: 0000000000000293 R08: 0000000000000001 R09: fffffbfff2dd01af
R10: ffffffff96e80d7f R11: 0000000000000006 R12: 1ffff92000022ef2
R13: 0000000000000293 R14: ffff888024efb940 R15: ffff88807f52a000
 spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
 tty_insert_flip_string_and_push_buffer+0x143/0x1f0 drivers/tty/tty_buffer.c:562
 pty_write+0xd2/0x100 drivers/tty/pty.c:118
 tty_put_char+0x12f/0x160 drivers/tty/tty_io.c:3168
 n_tty_process_echo_ops drivers/tty/n_tty.c:664 [inline]
 __process_echoes+0x80a/0xb40 drivers/tty/n_tty.c:709
 commit_echoes+0x147/0x210 drivers/tty/n_tty.c:772
 n_tty_receive_char+0x3d8/0x600 drivers/tty/n_tty.c:1437
 n_tty_receive_buf_standard+0x6aa/0x3180 drivers/tty/n_tty.c:1606
 __receive_buf drivers/tty/n_tty.c:1640 [inline]
 n_tty_receive_buf_common+0x8ed/0x1980 drivers/tty/n_tty.c:1739
 tty_ldisc_receive_buf+0xa2/0x190 drivers/tty/tty_buffer.c:387
 tty_port_default_receive_buf+0x70/0xb0 drivers/tty/tty_port.c:37
 receive_buf drivers/tty/tty_buffer.c:445 [inline]
 flush_to_ldisc+0x264/0x780 drivers/tty/tty_buffer.c:495
 process_one_work+0x9c5/0x1ba0 kernel/workqueue.c:3229
 process_scheduled_works kernel/workqueue.c:3310 [inline]
 worker_thread+0x6c8/0xf00 kernel/workqueue.c:3391
 kthread+0x2c1/0x3a0 kernel/kthread.c:389
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
rcu: rcu_preempt kthread starved for 10506 jiffies! g19481 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
rcu: 	Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt     state:R  running task     stack:27488 pid:17    tgid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5369 [inline]
 __schedule+0xe58/0x5ad0 kernel/sched/core.c:6756
 __schedule_loop kernel/sched/core.c:6833 [inline]
 schedule+0xe7/0x350 kernel/sched/core.c:6848
 schedule_timeout+0x124/0x280 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x1eb/0xb00 kernel/rcu/tree.c:2045
 rcu_gp_kthread+0x271/0x380 kernel/rcu/tree.c:2247
 kthread+0x2c1/0x3a0 kernel/kthread.c:389
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 1 UID: 0 PID: 7665 Comm: syz.4.686 Not tainted 6.12.0-syzkaller-09567-g7eef7e306d3c #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
RIP: 0010:write_comp_data+0x8b/0x90 kernel/kcov.c:272
Code: 00 00 4a 8d 34 dd 28 00 00 00 48 39 f2 72 1b 48 83 c7 01 48 89 38 4c 89 44 30 e0 4c 89 4c 30 e8 4c 89 54 30 f0 4a 89 4c d8 20 <c3> cc cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3
RSP: 0018:ffffc9000449fc10 EFLAGS: 00000297
RAX: 0000000000000002 RBX: ffff8880b86469c0 RCX: ffffffff8182b59c
RDX: ffff888027428000 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 0000000000000003 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000002 R12: ffffed10170c8d39
R13: 0000000000000001 R14: ffff8880b86469c8 R15: ffff8880b873fe40
FS:  00007f8112f016c0(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c3106e3 CR3: 000000001ce90000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 </IRQ>
 <TASK>
 csd_lock_wait kernel/smp.c:340 [inline]
 smp_call_function_many_cond+0x47c/0x1300 kernel/smp.c:884
 clock_was_set+0x646/0x850 kernel/time/hrtimer.c:963
 do_settimeofday64+0x305/0x4c0 kernel/time/timekeeping.c:1441
 do_sys_settimeofday64+0x1dc/0x260 kernel/time/time.c:195
 __do_sys_clock_settime kernel/time/posix-timers.c:1135 [inline]
 __se_sys_clock_settime kernel/time/posix-timers.c:1119 [inline]
 __x64_sys_clock_settime+0x1bf/0x2a0 kernel/time/posix-timers.c:1119
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f811217e819
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:00007f8112f01038 EFLAGS: 00000246 ORIG_RAX: 00000000000000e3
RAX: ffffffffffffffda RBX: 00007f8112335fa0 RCX: 00007f811217e819
RDX: 0000000000000000 RSI: 0000000020000040 RDI: 0000000000000000
RBP: 00007f81121f175e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f8112335fa0 R15: 00007ffc8f83f0c8
 </TASK>