syzbot

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-...!: (10500 ticks this GP) idle=a584/1/0x4000000000000000 softirq=23375/23375 fqs=559
	(t=10502 jiffies g=31721 q=160 ncpus=2)
rcu: rcu_preempt kthread starved for 8633 jiffies! g31721 f0x0 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:26432 pid:16    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 schedule+0xb9/0x180 kernel/sched/core.c:6637
 schedule_timeout+0x15c/0x280 kernel/time/timer.c:1965
 rcu_gp_fqs_loop+0x2f2/0x1310 kernel/rcu/tree.c:1706
 rcu_gp_kthread+0x95/0x380 kernel/rcu/tree.c:1905
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
NMI backtrace for cpu 0 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
NMI backtrace for cpu 0 skipped: idling at default_idle+0xb/0x10 arch/x86/kernel/process.c:741
CPU: 1 PID: 1277 Comm: aoe_tx0 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xa5/0x100 kernel/locking/spinlock.c:194
Code: 74 05 e8 fe d1 65 f7 48 c7 44 24 20 00 00 00 00 9c 8f 44 24 20 f6 44 24 21 02 75 4b f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> 66 5b 36 f7 65 8b 05 67 14 e1 75 85 c0 74 3c 48 c7 04 24 0e 36
RSP: 0018:ffffc900053ff8a0 EFLAGS: 00000206
RAX: 97990e0923783900 RBX: 0000000000000a06 RCX: 97990e0923783900
RDX: dffffc0000000000 RSI: ffffffff8a8c0500 RDI: 0000000000000001
RBP: ffffc900053ff920 R08: dffffc0000000000 R09: fffffbfff215c474
R10: fffffbfff215c474 R11: 1ffffffff215c473 R12: dffffc0000000000
R13: 1ffff1100ae29ec0 R14: ffffffff96f70f50 R15: 1ffff92000a7ff14
FS:  0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055904ad7e950 CR3: 0000000079409000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
 uart_write+0x469/0x910 drivers/tty/serial/serial_core.c:584
 handle_tx+0x23f/0x600 drivers/net/caif/caif_serial.c:236
 __netdev_start_xmit include/linux/netdevice.h:4896 [inline]
 netdev_start_xmit include/linux/netdevice.h:4910 [inline]
 xmit_one net/core/dev.c:3670 [inline]
 dev_hard_start_xmit+0x262/0x870 net/core/dev.c:3686
 __dev_queue_xmit+0x1bf1/0x3760 net/core/dev.c:4346
 dev_queue_xmit include/linux/netdevice.h:3051 [inline]
 tx+0x67/0x170 drivers/block/aoe/aoenet.c:63
 kthread+0x1c6/0x3b0 drivers/block/aoe/aoecmd.c:1241
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>