syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	(detected by 0, t=10502 jiffies, g=7097, q=12 ncpus=2)
rcu: All QSes seen, last rcu_preempt kthread activity 10500 (4294969452-4294958952), jiffies_till_next_fqs=1, root ->qsmask 0x0
rcu: rcu_preempt kthread starved for 10500 jiffies! g7097 f0x2 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:26256 pid:16    tgid:16    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5409 [inline]
 __schedule+0x17e8/0x4a50 kernel/sched/core.c:6746
 __schedule_loop kernel/sched/core.c:6823 [inline]
 schedule+0x14b/0x320 kernel/sched/core.c:6838
 schedule_timeout+0x1be/0x310 kernel/time/timer.c:2582
 rcu_gp_fqs_loop+0x2df/0x1370 kernel/rcu/tree.c:1663
 rcu_gp_kthread+0xa7/0x3b0 kernel/rcu/tree.c:1862
 kthread+0x2f2/0x390 kernel/kthread.c:388
 ret_from_fork+0x4d/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:
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 5127 Comm: syz-executor844 Not tainted 6.9.0-rc5-syzkaller-00031-g71b1543c83d6 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
RIP: 0010:rcu_is_watching+0x0/0xb0 kernel/rcu/tree.c:696
Code: 4c 89 f6 e8 82 71 6c 03 e9 2b ff ff ff e8 68 6b 03 0a 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 <f3> 0f 1e fa 41 57 41 56 53 65 ff 05 08 82 87 7e e8 9b 89 03 0a 89
RSP: 0018:ffffc90000a08bc0 EFLAGS: 00000046
RAX: 0000000000000001 RBX: 0000000000000000 RCX: ffff88807e7bbc00
RDX: ffff88807e7bbc00 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc90000a08c80 R08: ffffffff815c5b50 R09: 1ffffffff25e64a0
R10: dffffc0000000000 R11: fffffbfff25e64a1 R12: ffff888028658940
R13: 1ffff1100fcf78a2 R14: ffff88807e7bc510 R15: 1ffff92000141190
FS:  0000555584b6f3c0(0000) GS:ffff8880b9500000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000002006b000 CR3: 000000002281c000 CR4: 0000000000350ef0
Call Trace:
 <NMI>
 </NMI>
 <IRQ>
 rcu_read_lock_held_common kernel/rcu/update.c:109 [inline]
 rcu_read_lock_held+0x15/0x50 kernel/rcu/update.c:349
 __lock_task_sighand+0x119/0x2e0 kernel/signal.c:1399
 lock_task_sighand include/linux/sched/signal.h:746 [inline]
 send_sigqueue+0x25d/0x760 kernel/signal.c:1997
 posix_timer_event kernel/time/posix-timers.c:298 [inline]
 posix_timer_fn+0x18a/0x3a0 kernel/time/posix-timers.c:324
 __run_hrtimer kernel/time/hrtimer.c:1692 [inline]
 __hrtimer_run_queues+0x5a7/0xd50 kernel/time/hrtimer.c:1756
 hrtimer_interrupt+0x396/0x990 kernel/time/hrtimer.c:1818
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1032 [inline]
 __sysvec_apic_timer_interrupt+0x112/0x3f0 arch/x86/kernel/apic/apic.c:1049
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1043 [inline]
 sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1043
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:__raw_spin_unlock_irq include/linux/spinlock_api_smp.h:160 [inline]
RIP: 0010:_raw_spin_unlock_irq+0x29/0x50 kernel/locking/spinlock.c:202
Code: 90 f3 0f 1e fa 53 48 89 fb 48 83 c7 18 48 8b 74 24 08 e8 1a 18 e8 f5 48 89 df e8 32 58 e9 f5 e8 fd b4 12 f6 fb bf 01 00 00 00 <e8> f2 1d db f5 65 8b 05 63 4a 79 74 85 c0 74 06 5b e9 9c b7 25 00
RSP: 0018:ffffc900047ffc70 EFLAGS: 00000282
RAX: 63e827c788281200 RBX: ffff888028658940 RCX: ffffffff9472a603
RDX: dffffc0000000000 RSI: ffffffff8bcab8a0 RDI: 0000000000000001
RBP: ffffc900047ffdb0 R08: ffffffff8fa8e32f R09: 1ffffffff1f51c65
R10: dffffc0000000000 R11: fffffbfff1f51c66 R12: 0000000000000021
R13: 1ffff110050cb1bb R14: ffff888028658dd8 R15: ffff888028658940
 spin_unlock_irq include/linux/spinlock.h:401 [inline]
 get_signal+0x14dd/0x1740 kernel/signal.c:2914
 arch_do_signal_or_restart+0x96/0x860 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0xc9/0x370 kernel/entry/common.c:218
 do_syscall_64+0x102/0x240 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f84553a3e79
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 18 00 00 90 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fffe1fd3438 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 0000000000000003 RCX: 00007f84553a3e79
RDX: 000000002006b000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00000000000f4240 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000555584b6f370
R13: 0000000000000005 R14: 00007fffe1fd34b0 R15: 00007fffe1fd34a0
 </TASK>
INFO: NMI handler (nmi_cpu_backtrace_handler) took too long to run: 2.054 msecs