syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P189/1:b..l
rcu: 	(detected by 1, t=10503 jiffies, g=11977, q=703723 ncpus=2)
task:kworker/u4:5    state:R  running task     stack:23128 pid:189   ppid:2      flags:0x00004000
Workqueue: bat_events batadv_nc_worker
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1553/0x45a0 kernel/sched/core.c:6700
 preempt_schedule_irq+0xbf/0x150 kernel/sched/core.c:7010
 irqentry_exit+0x67/0x70 kernel/entry/common.c:438
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:lock_acquire+0x208/0x420 kernel/locking/lockdep.c:5758
Code: f7 84 24 80 00 00 00 00 02 00 00 43 c6 44 3c 04 f8 0f 85 f0 00 00 00 41 f7 c6 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 04 3c 00 00 00 00 43 c7 44 3c 08 00 00 00 00 65 48 8b 04 25
RSP: 0018:ffffc90002d47a40 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: 1fa1d5bd3ae4d800
RDX: 0000000000000000 RSI: ffffffff8acadd60 RDI: ffffffff8b1c9c20
RBP: ffffc90002d47b48 R08: dffffc0000000000 R09: 1ffffffff2239aa0
R10: dffffc0000000000 R11: fffffbfff2239aa1 R12: 1ffff920005a8f54
R13: ffffffff8d132160 R14: 0000000000000246 R15: dffffc0000000000
 rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 rcu_read_lock include/linux/rcupdate.h:786 [inline]
 batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:408 [inline]
 batadv_nc_worker+0xef/0x610 net/batman-adv/network-coding.c:719
 process_one_work kernel/workqueue.c:2653 [inline]
 process_scheduled_works+0xa5d/0x15d0 kernel/workqueue.c:2730
 worker_thread+0xa55/0xfc0 kernel/workqueue.c:2811
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
rcu: rcu_preempt kthread starved for 10529 jiffies! g11977 f0x2 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:27656 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1553/0x45a0 kernel/sched/core.c:6700
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 schedule_timeout+0x188/0x2d0 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x313/0x1590 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x9d/0x3b0 kernel/rcu/tree.c:1866
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 1 PID: 6377 Comm: syz.3.215 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:on_stack arch/x86/include/asm/stacktrace.h:55 [inline]
RIP: 0010:__unwind_start+0x5b3/0x7e0 arch/x86/kernel/unwind_orc.c:758
Code: c1 e8 03 48 89 04 24 4c 89 e8 48 c1 e8 03 48 89 44 24 08 48 89 6c 24 28 48 b8 00 00 00 00 00 fc ff df 48 8b 0c 24 80 3c 01 00 <74> 08 4c 89 ff e8 c3 ff a3 00 4d 8b 27 48 b8 00 00 00 00 00 fc ff
RSP: 0018:ffffc90005667660 EFLAGS: 00000246
RAX: dffffc0000000000 RBX: ffffc900056676c8 RCX: 1ffff92000acceda
RDX: ffff888022f78000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc90005667758 R08: ffffc90005667701 R09: 0000000000000000
R10: ffffc900056676c8 R11: fffff52000accee5 R12: ffffc90005667660
R13: ffffc900056676d8 R14: 1ffff92000acced9 R15: ffffc900056676d0
FS:  00007faf33e736c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000000 CR3: 0000000031d66000 CR4: 00000000003506e0
Call Trace:
 <TASK>
 unwind_start arch/x86/include/asm/unwind.h:64 [inline]
 arch_stack_walk+0xf8/0x190 arch/x86/kernel/stacktrace.c:24
 stack_trace_save+0xaa/0x100 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
 kasan_save_free_info+0x2e/0x50 mm/kasan/generic.c:522
 ____kasan_slab_free+0x126/0x1e0 mm/kasan/common.c:237
 kasan_slab_free include/linux/kasan.h:164 [inline]
 slab_free_hook mm/slub.c:1811 [inline]
 slab_free_freelist_hook+0x130/0x1a0 mm/slub.c:1837
 slab_free mm/slub.c:3830 [inline]
 kmem_cache_free+0xf8/0x270 mm/slub.c:3852
 file_free fs/file_table.c:77 [inline]
 __fput+0x61c/0x970 fs/file_table.c:397
 task_work_run+0x1d4/0x260 kernel/task_work.c:245
 get_signal+0x1235/0x13f0 kernel/signal.c:2678
 arch_do_signal_or_restart+0xc2/0x800 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7faf32f9ce59
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:00007faf33e73028 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: fffffffffffffe00 RBX: 00007faf33215fa0 RCX: 00007faf32f9ce59
RDX: 0000000000040100 RSI: 0000200000000000 RDI: ffffffffffffff9c
RBP: 00007faf33032d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007faf33216038 R14: 00007faf33215fa0 R15: 00007ffdbf5db2e8
 </TASK>
sched: RT throttling activated