syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	(detected by 1, t=10502 jiffies, g=43109, q=460 ncpus=2)
rcu: All QSes seen, last rcu_preempt kthread activity 10502 (4294980529-4294970027), jiffies_till_next_fqs=1, root ->qsmask 0x0
rcu: rcu_preempt kthread starved for 10502 jiffies! g43109 f0x2 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
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:27992 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5387 [inline]
 __schedule+0x10e9/0x6820 kernel/sched/core.c:7188
 __schedule_loop kernel/sched/core.c:7267 [inline]
 schedule+0xdd/0x390 kernel/sched/core.c:7282
 schedule_timeout+0x127/0x280 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x1a9/0x900 kernel/rcu/tree.c:2095
 rcu_gp_kthread+0x179/0x230 kernel/rcu/tree.c:2297
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 9433 Comm: syz.3.859 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:lockdep_enabled kernel/locking/lockdep.c:124 [inline]
RIP: 0010:lock_is_held_type+0x42/0x140 kernel/locking/lockdep.c:5933
Code: 8b 15 aa e6 80 08 85 d2 0f 85 de 00 00 00 41 57 41 56 41 55 41 54 55 53 48 83 ec 08 65 48 8b 2d 1c 9f 80 08 8b 95 8c 0b 00 00 <85> d2 0f 85 a7 00 00 00 48 89 fb 41 89 f4 9c 41 5d fa 48 c7 c7 21
RSP: 0018:ffffc90000007e18 EFLAGS: 00000096
RAX: 00000000ffffffff RBX: ffff8880b8428600 RCX: 0000000000000001
RDX: 0000000000000000 RSI: 00000000ffffffff RDI: ffff8880b84284d8
RBP: ffff88803414a500 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000001 R15: ffff8880b8428650
FS:  00007f6da78e06c0(0000) GS:ffff888124376000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc33ae72700 CR3: 0000000050faf000 CR4: 00000000003526f0
Call Trace:
 <IRQ>
 lock_is_held include/linux/lockdep.h:249 [inline]
 enqueue_hrtimer+0x24f/0x2f0 kernel/time/hrtimer.c:1107
 __run_hrtimer kernel/time/hrtimer.c:1946 [inline]
 __hrtimer_run_queues+0x73d/0xa00 kernel/time/hrtimer.c:1994
 hrtimer_interrupt+0x3e5/0x940 kernel/time/hrtimer.c:2113
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1050 [inline]
 __sysvec_apic_timer_interrupt+0x10b/0x460 arch/x86/kernel/apic/apic.c:1067
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1061 [inline]
 sysvec_apic_timer_interrupt+0x9e/0xc0 arch/x86/kernel/apic/apic.c:1061
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:179 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0x31/0x80 kernel/locking/spinlock.c:198
Code: f5 53 48 8b 74 24 10 48 89 fb 48 83 c7 18 e8 e6 84 57 f6 48 89 df e8 be d4 57 f6 f7 c5 00 02 00 00 75 23 9c 58 f6 c4 02 75 37 <bf> 01 00 00 00 e8 05 a8 47 f6 65 8b 05 fe ae 7d 08 85 c0 74 16 5b
RSP: 0018:ffffc900030a7838 EFLAGS: 00000246
RAX: 0000000000000006 RBX: ffff888035991800 RCX: 0000000000000040
RDX: 0000000000000000 RSI: ffffffff8df1fea8 RDI: ffffffff8c1c3600
RBP: 0000000000000286 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: ffff888035991690
R13: ffff888035991840 R14: ffff8880359911e8 R15: ffff8880271e4c80
 __unix_dgram_recvmsg+0x31a/0xc30 net/unix/af_unix.c:2612
 unix_dgram_recvmsg+0xcd/0x100 net/unix/af_unix.c:2686
 sock_recvmsg_nosec net/socket.c:1137 [inline]
 ____sys_recvmsg+0x5b3/0x640 net/socket.c:2916
 ___sys_recvmsg+0x16a/0x1a0 net/socket.c:2960
 do_recvmmsg+0x301/0x760 net/socket.c:3055
 __sys_recvmmsg net/socket.c:3129 [inline]
 __do_sys_recvmmsg net/socket.c:3152 [inline]
 __se_sys_recvmmsg net/socket.c:3145 [inline]
 __x64_sys_recvmmsg+0x22a/0x280 net/socket.c:3145
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x10b/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f6da699cdd9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f6da78e0028 EFLAGS: 00000246 ORIG_RAX: 000000000000012b
RAX: ffffffffffffffda RBX: 00007f6da6c16090 RCX: 00007f6da699cdd9
RDX: 00000000080002c1 RSI: 0000200000000040 RDI: 0000000000000009
RBP: 00007f6da6a32d69 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6da6c16128 R14: 00007f6da6c16090 R15: 00007ffda89c9158
 </TASK>