syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	(detected by 0, t=10502 jiffies, g=6417, q=46 ncpus=2)
rcu: All QSes seen, last rcu_preempt kthread activity 10503 (4294954340-4294943837), jiffies_till_next_fqs=1, root ->qsmask 0x0
rcu: rcu_preempt kthread starved for 10504 jiffies! g6417 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:27752 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5380 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
 schedule+0xbd/0x170 kernel/sched/core.c:6773
 schedule_timeout+0x160/0x280 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x302/0x1560 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x99/0x380 kernel/rcu/tree.c:1866
 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>
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: 5785 Comm: syz-executor510 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:check_wait_context kernel/locking/lockdep.c:4796 [inline]
RIP: 0010:__lock_acquire+0xa09/0x7c80 kernel/locking/lockdep.c:5087
Code: 00 00 4c 89 f0 48 c1 e8 03 42 0f b6 04 00 84 c0 0f 85 37 01 00 00 41 80 3e 02 0f 84 91 00 00 00 48 8b 44 24 78 42 0f b6 04 00 <84> c0 0f 85 ef 00 00 00 48 ff c3 48 8b 44 24 40 48 63 00 49 83 c7
RSP: 0018:ffffc900001f08c0 EFLAGS: 00000093
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000002
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff90d945d0
RBP: ffffc900001f0b08 R08: dffffc0000000000 R09: 1ffffffff21b28ba
R10: dffffc0000000000 R11: fffffbfff21b28bb R12: 0000000000000002
R13: ffff88802ea1e500 R14: ffffffff9075268a R15: ffff88802ea1e500
FS:  00005555914b13c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000020000006b000 CR3: 0000000076239000 CR4: 00000000003506e0
Call Trace:
 <IRQ>
 lock_acquire+0x197/0x410 kernel/locking/lockdep.c:5754
 rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 rcu_read_lock include/linux/rcupdate.h:786 [inline]
 send_sigqueue+0xb8/0x710 kernel/signal.c:1990
 posix_timer_event kernel/time/posix-timers.c:299 [inline]
 posix_timer_fn+0x16e/0x3d0 kernel/time/posix-timers.c:325
 __run_hrtimer kernel/time/hrtimer.c:1750 [inline]
 __hrtimer_run_queues+0x51e/0xc40 kernel/time/hrtimer.c:1814
 hrtimer_interrupt+0x3c9/0x9c0 kernel/time/hrtimer.c:1876
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1077 [inline]
 __sysvec_apic_timer_interrupt+0xfb/0x3b0 arch/x86/kernel/apic/apic.c:1094
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
 sysvec_apic_timer_interrupt+0x9f/0xc0 arch/x86/kernel/apic/apic.c:1088
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
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: 00 f3 0f 1e fa 53 48 89 fb 48 83 c7 18 48 8b 74 24 08 e8 6a 5f f6 f6 48 89 df e8 82 31 f7 f6 e8 5d d8 1a f7 fb bf 01 00 00 00 <e8> 52 53 ea f6 65 8b 05 43 9a 92 75 85 c0 74 02 5b c3 e8 20 80 8f
RSP: 0018:ffffc9000464fc78 EFLAGS: 00000286
RAX: 11c94c866c179900 RBX: ffff88807be99bc0 RCX: 11c94c866c179900
RDX: dffffc0000000000 RSI: ffffffff8aaabce0 RDI: 0000000000000001
RBP: ffff88807be9a058 R08: ffffffff8e4a212f R09: 1ffffffff1c94425
R10: dffffc0000000000 R11: fffffbfff1c94426 R12: 1ffff1100f7d340b
R13: 0000000000000021 R14: dffffc0000000000 R15: 0000000000000000
 spin_unlock_irq include/linux/spinlock.h:401 [inline]
 get_signal+0x11f5/0x1400 kernel/signal.c:2905
 arch_do_signal_or_restart+0x9c/0x7b0 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xf6/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:87
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fdb6b46c919
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 11 19 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:00007fff0f996b78 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 0000000000000003 RCX: 00007fdb6b46c919
RDX: 000020000006b000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 00007fdb6b42c990 R09: 00007fdb6b42c990
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fdb6b4ca33c
R13: 00007fdb6b4c4106 R14: 00007fff0f996bb0 R15: 0000000000000000
 </TASK>
INFO: NMI handler (nmi_cpu_backtrace_handler) took too long to run: 1.061 msecs