syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P4402/1:b..l P4178/1:b..l
	(detected by 1, t=10502 jiffies, g=7977, q=18)
task:syz-executor    state:R  running task     stack:20448 pid: 4178 ppid:  4165 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5029 [inline]
 __schedule+0x12c4/0x45b0 kernel/sched/core.c:6375
 preempt_schedule_irq+0xf7/0x1c0 kernel/sched/core.c:6779
 irqentry_exit+0x53/0x80 kernel/entry/common.c:432
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:xas_start+0x3f3/0x7b0 lib/xarray.c:193
Code: ac 45 fd 48 b8 00 00 00 00 00 fc ff df 41 80 3c 07 00 74 08 4c 89 f7 e8 6b 9f 8f fd 49 c7 06 01 00 00 00 31 ed e9 09 03 00 00 <e8> 88 ac 45 fd eb 05 e8 81 ac 45 fd 48 b8 00 00 00 00 00 fc ff df
RSP: 0018:ffffc90002f5f688 EFLAGS: 00000293
RAX: 0000000000000000 RBX: 000000000000000c RCX: ffff888076ae0000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000000000003f
RBP: 0000000000000000 R08: ffffffff843aefd2 R09: ffffffff843b66dc
R10: 0000000000000002 R11: ffff888076ae0000 R12: ffffc90002f5f7e8
R13: ffff888060bc18c2 R14: ffffc90002f5f7f8 R15: 1ffff920005ebeff
 xas_load lib/xarray.c:233 [inline]
 xas_find+0x173/0xaa0 lib/xarray.c:1249
 find_get_entry mm/filemap.c:1978 [inline]
 find_lock_entries+0x22a/0x1030 mm/filemap.c:2092
 shmem_undo_range+0x2a3/0x1b50 mm/shmem.c:943
 shmem_truncate_range mm/shmem.c:1063 [inline]
 shmem_evict_inode+0x21b/0xa00 mm/shmem.c:1145
 evict+0x529/0x930 fs/inode.c:647
 do_unlinkat+0x508/0x950 fs/namei.c:4355
 __do_sys_unlink fs/namei.c:4396 [inline]
 __se_sys_unlink fs/namei.c:4394 [inline]
 __x64_sys_unlink+0x45/0x50 fs/namei.c:4394
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f1b5116d717
RSP: 002b:00007ffd182b8d18 EFLAGS: 00000206 ORIG_RAX: 0000000000000057
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f1b5116d717
RDX: 00007ffd182b8d40 RSI: 00007ffd182b8dd0 RDI: 00007ffd182b8dd0
RBP: 00007ffd182b8dd0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000100 R11: 0000000000000206 R12: 00007ffd182b9e60
R13: 00007f1b511ef08c R14: 0000000000017d94 R15: 00007ffd182b9ea0
 </TASK>
task:kworker/u4:12   state:R  running task     stack:27328 pid: 4402 ppid:     2 flags:0x00004000
Workqueue: bat_events batadv_nc_worker
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5029 [inline]
 __schedule+0x12c4/0x45b0 kernel/sched/core.c:6375
 preempt_schedule_irq+0xf7/0x1c0 kernel/sched/core.c:6779
 irqentry_exit+0x53/0x80 kernel/entry/common.c:432
 asm_sysvec_reschedule_ipi+0x16/0x20 arch/x86/include/asm/idtentry.h:681
RIP: 0010:check_kcov_mode kernel/kcov.c:172 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x13/0x60 kernel/kcov.c:206
Code: 48 8b 3d 28 05 8a 0c 48 89 de 5b e9 37 1b 49 00 cc cc cc cc cc cc cc 48 8b 04 24 65 48 8b 0d f4 d2 81 7e 65 8b 15 f5 d2 81 7e <81> e2 00 01 ff 00 74 11 81 fa 00 01 00 00 75 35 83 b9 34 16 00 00
RSP: 0018:ffffc9000328fbf0 EFLAGS: 00000202
RAX: ffffffff8a1cc2f3 RBX: ffff888062e9c778 RCX: ffff888020d11dc0
RDX: 0000000080000000 RSI: ffffffff8af9fa60 RDI: ffffffff8af9fa20
RBP: 0000000000000001 R08: ffffffff8a1cc2e1 R09: fffffbfff2131e19
R10: 0000000000000000 R11: dffffc0000000001 R12: 00000000000000ef
R13: dffffc0000000000 R14: ffff888062f50c80 R15: ffff88807d21bc40
 rcu_read_lock include/linux/rcupdate.h:740 [inline]
 batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:412 [inline]
 batadv_nc_worker+0xe3/0x5b0 net/batman-adv/network-coding.c:723
 process_one_work+0x8a1/0x10c0 kernel/workqueue.c:2310
 worker_thread+0xaca/0x1280 kernel/workqueue.c:2457
 kthread+0x3f6/0x4f0 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>
rcu: rcu_preempt kthread starved for 10558 jiffies! g7977 f0x0 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:27000 pid:   15 ppid:     2 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5029 [inline]
 __schedule+0x12c4/0x45b0 kernel/sched/core.c:6375
 schedule+0x11b/0x1f0 kernel/sched/core.c:6458
 schedule_timeout+0x1b9/0x300 kernel/time/timer.c:1914
 rcu_gp_fqs_loop+0x2bf/0x1080 kernel/rcu/tree.c:1972
 rcu_gp_kthread+0xa4/0x360 kernel/rcu/tree.c:2145
 kthread+0x3f6/0x4f0 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
NMI backtrace for cpu 1
CPU: 1 PID: 4414 Comm: syz.4.42 Not tainted 5.15.179-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e3/0x2d0 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x46a/0x4a0 lib/nmi_backtrace.c:111
 nmi_trigger_cpumask_backtrace+0x181/0x2a0 lib/nmi_backtrace.c:62
 trigger_single_cpu_backtrace include/linux/nmi.h:166 [inline]
 rcu_check_gp_kthread_starvation+0x1d2/0x240 kernel/rcu/tree_stall.h:487
 print_other_cpu_stall+0x137a/0x14d0 kernel/rcu/tree_stall.h:592
 check_cpu_stall kernel/rcu/tree_stall.h:745 [inline]
 rcu_pending kernel/rcu/tree.c:3932 [inline]
 rcu_sched_clock_irq+0xa38/0x1150 kernel/rcu/tree.c:2619
 update_process_times+0x196/0x200 kernel/time/timer.c:1818
 tick_sched_handle kernel/time/tick-sched.c:254 [inline]
 tick_sched_timer+0x386/0x550 kernel/time/tick-sched.c:1473
 __run_hrtimer kernel/time/hrtimer.c:1688 [inline]
 __hrtimer_run_queues+0x55b/0xcf0 kernel/time/hrtimer.c:1752
 hrtimer_interrupt+0x392/0x980 kernel/time/hrtimer.c:1814
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1097 [inline]
 __sysvec_apic_timer_interrupt+0x13b/0x4b0 arch/x86/kernel/apic/apic.c:1114
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0x9b/0xc0 arch/x86/kernel/apic/apic.c:1108
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:__raw_spin_unlock_irq include/linux/spinlock_api_smp.h:169 [inline]
RIP: 0010:_raw_spin_unlock_irq+0x25/0x40 kernel/locking/spinlock.c:202
Code: 31 60 f6 ff 90 53 48 89 fb 48 83 c7 18 48 8b 74 24 08 e8 ce 67 19 f7 48 89 df e8 26 bc 1a f7 e8 11 7c 3d f7 fb bf 01 00 00 00 <e8> 16 00 0e f7 65 8b 05 87 d0 b8 75 85 c0 74 02 5b c3 e8 54 ed b6
RSP: 0018:ffffc9000316fbc0 EFLAGS: 00000282
RAX: 6f0e3b4bdb08e700 RBX: ffff888077598940 RCX: ffffffff96a95f03
RDX: dffffc0000000000 RSI: ffffffff8aab2a60 RDI: 0000000000000001
RBP: 0000000000000000 R08: ffffffff81871b70 R09: ffffed100eeb3129
R10: 0000000000000000 R11: dffffc0000000001 R12: 0000000000000021
R13: dffffc0000000000 R14: ffff888077598dd8 R15: ffff888077598940
 spin_unlock_irq include/linux/spinlock.h:413 [inline]
 get_signal+0x13ee/0x14e0 kernel/signal.c:2903
 arch_do_signal_or_restart+0xc3/0x1890 arch/x86/kernel/signal.c:867
 handle_signal_work kernel/entry/common.c:154 [inline]
 exit_to_user_mode_loop+0x97/0x130 kernel/entry/common.c:178
 exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:214
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x5d/0x240 kernel/entry/common.c:307
 do_syscall_64+0x47/0xb0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fa4fd006167
Code: ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89
RSP: 002b:00007fa4fae6f0e8 EFLAGS: 00000246
RAX: 00000000000000ca RBX: 00007fa4fd21efa8 RCX: 00007fa4fd006169
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007fa4fd21efa8
RBP: 00007fa4fd21efa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fa4fd21efac
R13: 0000000000000000 R14: 00007ffd26930f80 R15: 00007ffd26931068
 </TASK>