syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P6514/1:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=73437, q=565 ncpus=2)
task:kworker/u8:12   state:R  running task     stack:24648 pid:6514  tgid:6514  ppid:2      task_flags:0x4208060 flags:0x00080000
Workqueue: iou_exit io_ring_exit_work
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5295 [inline]
 __schedule+0xfee/0x6120 kernel/sched/core.c:6908
 preempt_schedule_irq+0x50/0x90 kernel/sched/core.c:7235
 irqentry_exit+0x17b/0x670 kernel/entry/common.c:239
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:__orc_find+0x3d/0xf0 arch/x86/kernel/unwind_orc.c:105
Code: 53 48 83 ec 08 85 d2 0f 84 99 00 00 00 49 89 fe 48 89 f0 49 39 fc 72 7b 48 b9 00 00 00 00 00 fc ff df 49 89 ff 48 89 fd eb 0c <48> 8d 6b 04 49 89 df 49 39 ec 72 4e 4c 89 e2 48 29 ea 48 89 d6 48
RSP: 0018:ffffc90003187588 EFLAGS: 00000206
RAX: ffffffff9179f9b4 RBX: ffffffff90f2c004 RCX: dffffc0000000000
RDX: ffffffff81d1f6f5 RSI: 0000000000000000 RDI: ffffffff90f2c004
RBP: ffffffff90f2c004 R08: ffffffff9179f9ba R09: 0000000000000007
R10: 0000000000000200 R11: 000000000000d1fa R12: ffffffff90f2c004
R13: ffffffff81d1fa4f R14: ffffffff90f2c004 R15: ffffffff90f2c004
 orc_find arch/x86/kernel/unwind_orc.c:238 [inline]
 unwind_next_frame+0x2ec/0x1ea0 arch/x86/kernel/unwind_orc.c:510
 arch_stack_walk+0x94/0xf0 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x8e/0xc0 kernel/stacktrace.c:122
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_record_aux_stack+0xa7/0xc0 mm/kasan/generic.c:556
 __call_rcu_common.constprop.0+0xa5/0x9b0 kernel/rcu/tree.c:3131
 slab_free_hook mm/slub.c:2656 [inline]
 slab_free mm/slub.c:6143 [inline]
 kmem_cache_free+0x44b/0x6a0 mm/slub.c:6273
 __io_req_caches_free+0x1a6/0x220 io_uring/io_uring.c:2133
 io_req_caches_free+0x24/0x60 io_uring/io_uring.c:2145
 io_ring_exit_work+0x3eb/0xce9 io_uring/io_uring.c:2339
 process_one_work+0x9d7/0x1920 kernel/workqueue.c:3275
 process_scheduled_works kernel/workqueue.c:3358 [inline]
 worker_thread+0x5da/0xe40 kernel/workqueue.c:3439
 kthread+0x370/0x450 kernel/kthread.c:467
 ret_from_fork+0x754/0xd80 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
rcu: rcu_preempt kthread timer wakeup didn't happen for 10536 jiffies! g73437 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: 	Possible timer handling issue on cpu=1 timer-softirq=79202
rcu: rcu_preempt kthread starved for 10537 jiffies! g73437 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->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:I stack:27976 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5295 [inline]
 __schedule+0xfee/0x6120 kernel/sched/core.c:6908
 __schedule_loop kernel/sched/core.c:6990 [inline]
 schedule+0xdd/0x390 kernel/sched/core.c:7005
 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:467
 ret_from_fork+0x754/0xd80 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:
CPU: 1 UID: 0 PID: 1296 Comm: aoe_tx0 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
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:194
Code: f5 53 48 8b 74 24 10 48 89 fb 48 83 c7 18 e8 56 21 52 f6 48 89 df e8 3e 71 52 f6 f7 c5 00 02 00 00 75 23 9c 58 f6 c4 02 75 37 <bf> 01 00 00 00 e8 c5 90 42 f6 65 8b 05 5e ee 7a 08 85 c0 74 16 5b
RSP: 0018:ffffc90004e9f968 EFLAGS: 00000246
RAX: 0000000000000006 RBX: ffffffff9b4a14c0 RCX: 0000000000000004
RDX: 0000000000000000 RSI: ffffffff8de72ef9 RDI: ffffffff8c1af6a0
RBP: 0000000000000293 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: ffffffff8f512ba0
R13: ffffffff9b4a15c8 R14: 0000000000000000 R15: ffffffff9b4a1600
FS:  0000000000000000(0000) GS:ffff888124445000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fceb4f1c008 CR3: 00000000829f9000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 spin_unlock_irqrestore include/linux/spinlock.h:407 [inline]
 uart_port_unlock_irqrestore include/linux/serial_core.h:788 [inline]
 uart_port_unlock_deref drivers/tty/serial/serial_core.c:91 [inline]
 uart_port_unlock_deref drivers/tty/serial/serial_core.c:88 [inline]
 uart_write_room+0x2d2/0x930 drivers/tty/serial/serial_core.c:647
 tty_write_room+0x66/0x90 drivers/tty/tty_ioctl.c:69
 handle_tx+0x14a/0x620 drivers/net/caif/caif_serial.c:212
 __netdev_start_xmit include/linux/netdevice.h:5275 [inline]
 netdev_start_xmit include/linux/netdevice.h:5284 [inline]
 xmit_one net/core/dev.c:3871 [inline]
 dev_hard_start_xmit+0x121/0x7d0 net/core/dev.c:3887
 __dev_queue_xmit+0x32c1/0x4800 net/core/dev.c:4840
 dev_queue_xmit include/linux/netdevice.h:3384 [inline]
 tx+0xc4/0x130 drivers/block/aoe/aoenet.c:62
 kthread+0x1d8/0x3c0 drivers/block/aoe/aoecmd.c:1241
 kthread+0x370/0x450 kernel/kthread.c:467
 ret_from_fork+0x754/0xd80 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>