syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P19615/2:b..l
rcu: 	(detected by 0, t=10502 jiffies, g=144637, q=440 ncpus=1)
task:syz.3.3440      state:R  running task     stack:26408 pid:19615 tgid:19615 ppid:15498  task_flags:0x40064c flags:0x00080001
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:lock_release+0x19e/0x320 kernel/locking/lockdep.c:5893
Code: ff 65 0f c1 05 cb 13 29 12 83 f8 01 0f 85 3d 01 00 00 9c 58 f6 c4 02 0f 85 28 01 00 00 41 f7 c6 00 02 00 00 0f 85 de 00 00 00 <48> 8b 44 24 10 65 48 2b 05 1d cc 28 12 0f 85 63 01 00 00 48 83 c4
RSP: 0000:ffffc900044e7230 EFLAGS: 00000206
RAX: 0000000000000046 RBX: ffffffff8e7e7460 RCX: ffffc900044e723c
RDX: 0000000000000001 RSI: ffffffff8de57654 RDI: ffffffff8c1afaa0
RBP: ffffffff8240f718 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: ffff888028925b80
R13: 0000000000000001 R14: 0000000000000202 R15: 0000000000000002
 rcu_lock_release include/linux/rcupdate.h:322 [inline]
 rcu_read_unlock include/linux/rcupdate.h:881 [inline]
 page_ref_add_unless.constprop.0+0x11d/0x390 include/linux/page_ref.h:239
 folio_ref_add_unless include/linux/page_ref.h:248 [inline]
 folio_try_get include/linux/page_ref.h:264 [inline]
 find_get_entry mm/filemap.c:2081 [inline]
 find_lock_entries+0x1c5/0x1130 mm/filemap.c:2171
 shmem_undo_range+0x212/0x1570 mm/shmem.c:1131
 shmem_truncate_range mm/shmem.c:1277 [inline]
 shmem_evict_inode+0x39e/0xbd0 mm/shmem.c:1407
 evict+0x3c2/0xad0 fs/inode.c:846
 iput_final fs/inode.c:1966 [inline]
 iput.part.0+0x605/0xf50 fs/inode.c:2015
 iput+0x35/0x40 fs/inode.c:1981
 dentry_unlink_inode+0x2a1/0x490 fs/dcache.c:467
 __dentry_kill+0x1d0/0x600 fs/dcache.c:670
 finish_dput+0x76/0x480 fs/dcache.c:879
 dput.part.0+0x456/0x570 fs/dcache.c:928
 dput+0x1f/0x30 fs/dcache.c:920
 __fput+0x519/0xb40 fs/file_table.c:477
 task_work_run+0x150/0x240 kernel/task_work.c:233
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x8b8/0x2b60 kernel/exit.c:976
 do_group_exit+0xd5/0x2a0 kernel/exit.c:1118
 get_signal+0x1ec7/0x21e0 kernel/signal.c:3034
 arch_do_signal_or_restart+0x91/0x770 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:98 [inline]
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
 irqentry_exit_to_user_mode_prepare include/linux/irq-entry-common.h:270 [inline]
 irqentry_exit_to_user_mode include/linux/irq-entry-common.h:339 [inline]
 irqentry_exit+0x1f8/0x670 kernel/entry/common.c:219
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
RIP: 0033:0x4021000
RSP: 002b:000000000000000e EFLAGS: 00010246
RAX: 0000000000000000 RBX: 00007fab58a15fa0 RCX: 00007fab5879c799
RDX: 0000000000000000 RSI: 0000000000000006 RDI: 0000000000000004
RBP: 00007fab58832c99 R08: 0000000000000007 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fab58a16038 R14: 00007fab58a15fa0 R15: 00007fff7e32f748
 </TASK>
rcu: rcu_preempt kthread timer wakeup didn't happen for 10501 jiffies! g144637 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: 	Possible timer handling issue on cpu=0 timer-softirq=66533
rcu: rcu_preempt kthread starved for 10502 jiffies! g144637 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->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:I stack:27832 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:436
 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: 0 UID: 0 PID: 1300 Comm: aoe_tx0 Tainted: G     U       L      syzkaller #0 PREEMPT(full) 
Tainted: [U]=USER, [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/27/2026
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 96 90 54 f6 48 89 df e8 7e e0 54 f6 f7 c5 00 02 00 00 75 23 9c 58 f6 c4 02 75 37 <bf> 01 00 00 00 e8 55 fd 44 f6 65 8b 05 5e 5e 7d 08 85 c0 74 16 5b
RSP: 0018:ffffc9000581f968 EFLAGS: 00000246
RAX: 0000000000000002 RBX: ffffffff9b48b7c0 RCX: 0000000000000004
RDX: 0000000000000000 RSI: ffffffff8de7d6d8 RDI: ffffffff8c1afaa0
RBP: 0000000000000293 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: ffffffff8f514160
R13: ffffffff9b48b8c8 R14: 0000000000000000 R15: ffffffff9b48b900
FS:  0000000000000000(0000) GS:ffff88812434d000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000004021000 CR3: 0000000035270000 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:5292 [inline]
 netdev_start_xmit include/linux/netdevice.h:5301 [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:4837
 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:436
 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>