syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P6934/1:b..l P6471/1:b..l
rcu: 	(detected by 0, t=10503 jiffies, g=20853, q=260 ncpus=2)
task:syz.1.197       state:R  running task     stack:22888 pid:6471  ppid:5795   flags:0x00404006
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5380 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
 preempt_schedule_irq+0xb5/0x140 kernel/sched/core.c:7009
 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:arch_atomic_try_cmpxchg arch/x86/include/asm/atomic.h:115 [inline]
RIP: 0010:raw_atomic_try_cmpxchg include/linux/atomic/atomic-arch-fallback.h:2112 [inline]
RIP: 0010:raw_atomic_fetch_add_unless include/linux/atomic/atomic-arch-fallback.h:2409 [inline]
RIP: 0010:raw_atomic_add_unless include/linux/atomic/atomic-arch-fallback.h:2433 [inline]
RIP: 0010:atomic_add_unless include/linux/atomic/atomic-instrumented.h:1508 [inline]
RIP: 0010:page_ref_add_unless include/linux/page_ref.h:238 [inline]
RIP: 0010:folio_ref_add_unless include/linux/page_ref.h:247 [inline]
RIP: 0010:folio_try_get include/linux/page_ref.h:263 [inline]
RIP: 0010:find_get_entry mm/filemap.c:2027 [inline]
RIP: 0010:find_lock_entries+0x263/0xfe0 mm/filemap.c:2114
Code: 0f 85 09 05 00 00 41 8b 1e 31 ff 89 de e8 a5 d3 d1 ff 85 db 0f 84 c7 04 00 00 8d 4b 01 31 f6 89 d8 f0 41 0f b1 0e 41 0f 94 c4 <40> 0f 94 c6 89 c3 bf 02 00 00 00 e8 5d d2 d1 ff 45 84 e4 0f 85 09
RSP: 0018:ffffc9000bee72a0 EFLAGS: 00000246
RAX: 0000000000000001 RBX: 0000000000000001 RCX: 0000000000000002
RDX: ffff888020e09e00 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc9000bee73d0 R08: ffffea0001099177 R09: 1ffffd400021322e
R10: dffffc0000000000 R11: fffff9400021322f R12: ffffc9000bee7301
R13: 1ffffd400021322e R14: ffffea0001099174 R15: ffffea0001099140
 shmem_undo_range+0x254/0x1a40 mm/shmem.c:1009
 shmem_truncate_range mm/shmem.c:1136 [inline]
 shmem_evict_inode+0x273/0xa70 mm/shmem.c:1265
 evict+0x486/0x870 fs/inode.c:705
 __dentry_kill+0x431/0x650 fs/dcache.c:611
 dentry_kill+0xb8/0x290 fs/dcache.c:-1
 dput+0xfe/0x1e0 fs/dcache.c:918
 __fput+0x5e5/0x970 fs/file_table.c:392
 task_work_run+0x1ce/0x250 kernel/task_work.c:239
 exit_task_work include/linux/task_work.h:43 [inline]
 do_exit+0x90b/0x23c0 kernel/exit.c:883
 do_group_exit+0x21b/0x2d0 kernel/exit.c:1024
 get_signal+0x12fc/0x1400 kernel/signal.c:2902
 arch_do_signal_or_restart+0x96/0x780 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xf6/0x180 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:87
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fd29c1c1465
RSP: 002b:00007fd29a3d4f80 EFLAGS: 00000293 ORIG_RAX: 00000000000000e6
RAX: fffffffffffffdfc RBX: 00007fd29c3d6090 RCX: 00007fd29c1c1465
RDX: 00007fd29a3d4fc0 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007fd29c211e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000000
R13: 00007fd29c3d6128 R14: 00007fd29c3d6090 R15: 00007ffea99c80f8
 </TASK>
task:syz-executor    state:R  running task     stack:23496 pid:6934  ppid:6905   flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5380 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
 preempt_schedule_common+0x82/0xc0 kernel/sched/core.c:6866
 preempt_schedule+0xab/0xc0 kernel/sched/core.c:6890
 preempt_schedule_thunk+0x1a/0x30 arch/x86/entry/thunk_64.S:45
 __raw_spin_unlock include/linux/spinlock_api_smp.h:143 [inline]
 _raw_spin_unlock+0x3a/0x40 kernel/locking/spinlock.c:186
 spin_unlock include/linux/spinlock.h:391 [inline]
 __d_lookup+0x299/0x7c0 fs/dcache.c:2508
 lookup_fast+0x7c/0x4d0 fs/namei.c:1652
 walk_component fs/namei.c:1998 [inline]
 link_path_walk+0x5ff/0xe00 fs/namei.c:2329
 path_openat+0x283/0x3190 fs/namei.c:3785
 do_filp_open+0x1c5/0x3d0 fs/namei.c:3816
 do_sys_openat2+0x12c/0x1c0 fs/open.c:1419
 do_sys_open fs/open.c:1434 [inline]
 __do_sys_openat fs/open.c:1450 [inline]
 __se_sys_openat fs/open.c:1445 [inline]
 __x64_sys_openat+0x139/0x160 fs/open.c:1445
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f1c3c78d510
RSP: 002b:00007ffd18fbaca0 EFLAGS: 00000293 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 0000000000080001 RCX: 00007f1c3c78d510
RDX: 0000000000080001 RSI: 00007f1c3c7efc18 RDI: 00000000ffffff9c
RBP: 00007f1c3c7efc18 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000007
R13: 00007ffd18fbad40 R14: 0000000000000009 R15: 0000000000000000
 </TASK>
rcu: rcu_preempt kthread starved for 10577 jiffies! g20853 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:26920 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5380 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
 schedule+0xbd/0x170 kernel/sched/core.c:6773
 schedule_timeout+0x160/0x280 kernel/time/timer.c:2167
 rcu_gp_fqs_loop+0x302/0x1560 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x99/0x380 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: 0 PID: 6940 Comm: syz.2.329 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
RIP: 0010:__raw_spin_unlock_irq include/linux/spinlock_api_smp.h:160 [inline]
RIP: 0010:_raw_spin_unlock_irq+0x29/0x50 kernel/locking/spinlock.c:202
Code: 00 f3 0f 1e fa 53 48 89 fb 48 83 c7 18 48 8b 74 24 08 e8 2a c0 ef f6 48 89 df e8 42 92 f0 f6 e8 4d 31 14 f7 fb bf 01 00 00 00 <e8> 52 a9 e3 f6 65 8b 05 a3 f7 8b 75 85 c0 74 02 5b c3 e8 80 d9 88
RSP: 0018:ffffc900039a7b68 EFLAGS: 00000286
RAX: a518acc17b1e1000 RBX: ffff888078ca3608 RCX: a518acc17b1e1000
RDX: dffffc0000000000 RSI: ffffffff8aaabca0 RDI: 0000000000000001
RBP: 00000000fffffe00 R08: ffffffff8e4a94ef R09: 1ffffffff1c9529d
R10: dffffc0000000000 R11: fffffbfff1c9529e R12: ffff888078ca3648
R13: dffffc0000000000 R14: ffff88802d803c00 R15: dffffc0000000000
FS:  00007fbb8a2616c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f1c3c7efc18 CR3: 000000006741d000 CR4: 00000000003506f0
Call Trace:
 <TASK>
 spin_unlock_irq include/linux/spinlock.h:401 [inline]
 do_wait_intr_irq+0x1ba/0x1e0 kernel/sched/wait.c:379
 eventfd_read+0x2b4/0x770 fs/eventfd.c:242
 call_read_iter include/linux/fs.h:2012 [inline]
 new_sync_read fs/read_write.c:389 [inline]
 vfs_read+0x431/0x920 fs/read_write.c:470
 ksys_read+0x147/0x250 fs/read_write.c:613
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fbb8938eba9
Code: 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 01 48
RSP: 002b:00007fbb8a261038 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007fbb895d5fa0 RCX: 00007fbb8938eba9
RDX: 0000000000000008 RSI: 0000200000000000 RDI: 0000000000000003
RBP: 00007fbb89411e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fbb895d6038 R14: 00007fbb895d5fa0 R15: 00007fffd8721ef8
 </TASK>