syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P4272/1:b..l
	(detected by 1, t=10502 jiffies, g=22165, q=47 ncpus=2)
task:syz-executor    state:R  running task     stack:22352 pid:4272  ppid:4269   flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5245 [inline]
 __schedule+0x11d1/0x40e0 kernel/sched/core.c:6562
 preempt_schedule_irq+0xbb/0x160 kernel/sched/core.c:6874
 irqentry_exit+0x63/0x70 kernel/entry/common.c:439
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:get_current arch/x86/include/asm/current.h:15 [inline]
RIP: 0010:write_comp_data kernel/kcov.c:244 [inline]
RIP: 0010:__sanitizer_cov_trace_const_cmp1+0x4/0x80 kernel/kcov.c:299
Code: 77 1e 49 ff c0 4c 89 02 48 c7 44 0a 08 06 00 00 00 48 89 7c 0a 10 48 89 74 0a 18 48 89 44 0a 20 c3 0f 1f 44 00 00 48 8b 04 24 <65> 48 8b 15 84 f7 7f 7e 65 8b 0d 85 f7 7f 7e 81 e1 00 01 ff 00 74
RSP: 0018:ffffc90004117760 EFLAGS: 00000246
RAX: ffffffff8a20f29d RBX: dffffc0000000000 RCX: 0000000000000007
RDX: ffffffff8a20f12f RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffff88802f900000 R09: 0000000000000002
R10: 0000000000000003 R11: 0000000000000000 R12: ffffc90004117878
R13: 000000000000152d R14: ffffc90004117868 R15: ffffc90004117860
 xas_find+0x27d/0xab0 lib/xarray.c:1255
 find_get_entry mm/filemap.c:2031 [inline]
 find_lock_entries+0x1c8/0xbb0 mm/filemap.c:2123
 shmem_undo_range+0x288/0x20c0 mm/shmem.c:925
 shmem_truncate_range mm/shmem.c:1062 [inline]
 shmem_evict_inode+0x25b/0xa80 mm/shmem.c:1171
 evict+0x4c9/0x8d0 fs/inode.c:705
 do_unlinkat+0x388/0x580 fs/namei.c:4405
 __do_sys_unlink fs/namei.c:4446 [inline]
 __se_sys_unlink fs/namei.c:4444 [inline]
 __x64_sys_unlink+0x45/0x50 fs/namei.c:4444
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fba1e59bec7
RSP: 002b:00007ffd6cf40668 EFLAGS: 00000206 ORIG_RAX: 0000000000000057
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fba1e59bec7
RDX: 00007ffd6cf40690 RSI: 00007ffd6cf40720 RDI: 00007ffd6cf40720
RBP: 00007ffd6cf40720 R08: 00007ffd6cf41720 R09: 00000000ffffffff
R10: 0000000000000100 R11: 0000000000000206 R12: 00007ffd6cf417b0
R13: 00007fba1e632120 R14: 00000000000628fc R15: 00007ffd6cf417f0
 </TASK>
rcu: rcu_preempt kthread starved for 10534 jiffies! g22165 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:26864 pid:16    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5245 [inline]
 __schedule+0x11d1/0x40e0 kernel/sched/core.c:6562
 schedule+0xb9/0x180 kernel/sched/core.c:6638
 schedule_timeout+0x184/0x2d0 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x303/0x1340 kernel/rcu/tree.c:1706
 rcu_gp_kthread+0x99/0x3b0 kernel/rcu/tree.c:1905
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 1 PID: 0 Comm: swapper/1 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:default_idle+0xb/0x10 arch/x86/kernel/process.c:742
Code: 48 89 df e8 77 a3 9b f7 e9 44 ff ff ff e8 3d 07 f6 ff 00 00 cc cc 00 00 cc cc 00 00 cc cc 00 66 90 0f 00 2d a7 ca 4e 00 fb f4 <c3> 0f 1f 40 00 41 57 41 56 53 49 be 00 00 00 00 00 fc ff df 65 48
RSP: 0018:ffffc90000177de8 EFLAGS: 000002c6
RAX: bab3d05e8a0ff900 RBX: ffffffff8a37e307 RCX: bab3d05e8a0ff900
RDX: 0000000000000001 RSI: ffffffff8a8c1120 RDI: ffffffff8adf1320
RBP: ffffc90000177f20 R08: ffff8880b8f3580b R09: 1ffff110171e6b01
R10: dffffc0000000000 R11: ffffed10171e6b02 R12: 0000000000000000
R13: dffffc0000000000 R14: ffff8880176c9dc0 R15: 1ffff9200002efc8
FS:  0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2eb3fea4c0 CR3: 000000002f8b7000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 default_idle_call+0x84/0xc0 kernel/sched/idle.c:109
 cpuidle_idle_call kernel/sched/idle.c:199 [inline]
 do_idle+0x250/0x680 kernel/sched/idle.c:323
 cpu_startup_entry+0x3f/0x60 kernel/sched/idle.c:422
 start_secondary+0xe4/0xf0 arch/x86/kernel/smpboot.c:281
 secondary_startup_64_no_verify+0xcf/0xdb
 </TASK>