syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P5881/1:b..l P6386/3:b..l P6363/1:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=13437, q=959 ncpus=2)
task:syz.1.80        state:R  running task     stack:23368 pid:6363  tgid:6362  ppid:5864   task_flags:0x400140 flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5357 [inline]
 __schedule+0x1798/0x4cc0 kernel/sched/core.c:6961
 preempt_schedule_irq+0xb5/0x150 kernel/sched/core.c:7288
 irqentry_exit+0x6f/0x90 kernel/entry/common.c:197
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:rcu_read_lock_held_common kernel/rcu/update.c:105 [inline]
RIP: 0010:rcu_read_lock_held+0xc/0x50 kernel/rcu/update.c:349
Code: 66 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 53 e8 e6 fc d4 09 85 c0 <74> 26 31 db e8 eb 2d 01 00 84 c0 74 20 e8 62 76 01 00 84 c0 74 17
RSP: 0018:ffffc90003aaf608 EFLAGS: 00000202
RAX: 0000000000000001 RBX: ffff8880552f6c02 RCX: ffff88802c2bbc00
RDX: ffff88802c2bbc00 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffff81f6a26d
R10: dffffc0000000000 R11: fffff52000755ee7 R12: ffff88807e706e08
R13: ffffc90003aaf718 R14: ffffc90003aaf700 R15: 1ffff92000755ee3
 xa_head include/linux/xarray.h:1210 [inline]
 xas_start+0x295/0x770 lib/xarray.c:191
 xas_load+0x2c/0x5b0 lib/xarray.c:239
 filemap_get_entry+0x168/0x2f0 mm/filemap.c:1871
 __filemap_get_folio+0x68/0xaf0 mm/filemap.c:1916
 write_begin_get_folio include/linux/pagemap.h:776 [inline]
 ext4_da_write_begin+0x641/0xda0 fs/ext4/inode.c:3145
 generic_perform_write+0x2c5/0x900 mm/filemap.c:4175
 ext4_buffered_write_iter+0xce/0x3a0 fs/ext4/file.c:299
 ext4_file_write_iter+0x298/0x1bc0 fs/ext4/file.c:-1
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x5c9/0xb30 fs/read_write.c:686
 ksys_pwrite64 fs/read_write.c:793 [inline]
 __do_sys_pwrite64 fs/read_write.c:801 [inline]
 __se_sys_pwrite64 fs/read_write.c:798 [inline]
 __x64_sys_pwrite64+0x193/0x220 fs/read_write.c:798
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ff30d98eba9
RSP: 002b:00007ff30bbf6038 EFLAGS: 00000246 ORIG_RAX: 0000000000000012
RAX: ffffffffffffffda RBX: 00007ff30dbd5fa0 RCX: 00007ff30d98eba9
RDX: 00000000200000c1 RSI: 00002000000000c0 RDI: 0000000000000004
RBP: 00007ff30da11e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000009000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ff30dbd6038 R14: 00007ff30dbd5fa0 R15: 00007ffc39bbd078
 </TASK>
task:modprobe        state:R  running task     stack:23992 pid:6386  tgid:6386  ppid:12     task_flags:0x400000 flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5357 [inline]
 __schedule+0x1798/0x4cc0 kernel/sched/core.c:6961
 preempt_schedule_common+0x83/0xd0 kernel/sched/core.c:7145
 preempt_schedule+0xae/0xc0 kernel/sched/core.c:7169
 preempt_schedule_thunk+0x16/0x30 arch/x86/entry/thunk.S:12
 __raw_spin_unlock include/linux/spinlock_api_smp.h:143 [inline]
 _raw_spin_unlock+0x3f/0x50 kernel/locking/spinlock.c:186
 spin_unlock include/linux/spinlock.h:391 [inline]
 filemap_map_pages+0x1121/0x1740 mm/filemap.c:3791
 do_fault_around mm/memory.c:5531 [inline]
 do_read_fault mm/memory.c:5564 [inline]
 do_fault mm/memory.c:5707 [inline]
 do_pte_missing mm/memory.c:4234 [inline]
 handle_pte_fault mm/memory.c:6052 [inline]
 __handle_mm_fault+0x34ac/0x5440 mm/memory.c:6195
 handle_mm_fault+0x40a/0x8e0 mm/memory.c:6364
 do_user_addr_fault+0xa81/0x1390 arch/x86/mm/fault.c:1336
 handle_page_fault arch/x86/mm/fault.c:1476 [inline]
 exc_page_fault+0x76/0xf0 arch/x86/mm/fault.c:1532
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
RIP: 0033:0x7f5760e65f35
RSP: 002b:00007ffc1b171ad8 EFLAGS: 00010287
RAX: 00000000ffffffcc RBX: 000055c542b61000 RCX: 00000000000003f0
RDX: 0000000000000000 RSI: 00007f5760f8e3f0 RDI: 00007ffc1b172fac
RBP: 00007ffc1b171c28 R08: 0000000000000000 R09: 00007f5760fc5a60
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffc1b171c50 R14: 00007f5760ff6000 R15: 000055c542b62d98
 </TASK>
task:syz-executor    state:R  running task     stack:21224 pid:5881  tgid:5881  ppid:5861   task_flags:0x400140 flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5357 [inline]
 __schedule+0x1798/0x4cc0 kernel/sched/core.c:6961
 preempt_schedule_common+0x83/0xd0 kernel/sched/core.c:7145
 preempt_schedule+0xae/0xc0 kernel/sched/core.c:7169
 preempt_schedule_thunk+0x16/0x30 arch/x86/entry/thunk.S:12
 __raw_spin_unlock include/linux/spinlock_api_smp.h:143 [inline]
 _raw_spin_unlock+0x3f/0x50 kernel/locking/spinlock.c:186
 spin_unlock include/linux/spinlock.h:391 [inline]
 wp_page_copy mm/memory.c:3653 [inline]
 do_wp_page+0x1d1d/0x5800 mm/memory.c:4013
 handle_pte_fault mm/memory.c:6068 [inline]
 __handle_mm_fault+0x1033/0x5440 mm/memory.c:6195
 handle_mm_fault+0x40a/0x8e0 mm/memory.c:6364
 do_user_addr_fault+0xa81/0x1390 arch/x86/mm/fault.c:1336
 handle_page_fault arch/x86/mm/fault.c:1476 [inline]
 exc_page_fault+0x76/0xf0 arch/x86/mm/fault.c:1532
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
RIP: 0033:0x7fea7194d02f
RSP: 002b:00007ffc29cf5e30 EFLAGS: 00010206
RAX: 0000000000018a41 RBX: 0000000000008040 RCX: 000055555fba3590
RDX: 0000000000008041 RSI: 000055555fbab5c0 RDI: 0000000000000004
RBP: 00007fea71ba7cc0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000001000 R11: 0000000000000802 R12: 0000000000008030
R13: 0000000000000076 R14: 00007fea71ba7d20 R15: 0000000000000000
 </TASK>
rcu: rcu_preempt kthread starved for 10589 jiffies! g13437 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:27160 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5357 [inline]
 __schedule+0x1798/0x4cc0 kernel/sched/core.c:6961
 __schedule_loop kernel/sched/core.c:7043 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:7058
 schedule_timeout+0x12b/0x270 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x301/0x1540 kernel/rcu/tree.c:2083
 rcu_gp_kthread+0x99/0x390 kernel/rcu/tree.c:2285
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
RIP: 0010:pv_native_safe_halt+0x13/0x20 arch/x86/kernel/paravirt.c:82
Code: 3e 1d 96 f5 cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d 73 07 0e 00 f3 0f 1e fa fb f4 <e9> 13 1d 96 f5 cc cc cc cc cc cc cc cc 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc90000197de0 EFLAGS: 000002c2
RAX: 37e300b760e20d00 RBX: ffffffff819683f8 RCX: 37e300b760e20d00
RDX: 0000000000000001 RSI: ffffffff8d9b9313 RDI: ffffffff8be33980
RBP: ffffc90000197f20 R08: ffff8880b8732f9b R09: 1ffff110170e65f3
R10: dffffc0000000000 R11: ffffed10170e65f4 R12: ffffffff8fa3a030
R13: 0000000000000001 R14: 0000000000000001 R15: 1ffff110039d9b40
FS:  0000000000000000(0000) GS:ffff888125d15000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000152000 CR3: 0000000074a11000 CR4: 0000000000350ef0
Call Trace:
 <TASK>
 arch_safe_halt arch/x86/include/asm/paravirt.h:107 [inline]
 default_idle+0x13/0x20 arch/x86/kernel/process.c:757
 default_idle_call+0x74/0xb0 kernel/sched/idle.c:122
 cpuidle_idle_call kernel/sched/idle.c:190 [inline]
 do_idle+0x1e8/0x510 kernel/sched/idle.c:330
 cpu_startup_entry+0x44/0x60 kernel/sched/idle.c:428
 start_secondary+0x101/0x110 arch/x86/kernel/smpboot.c:315
 common_startup_64+0x13e/0x147
 </TASK>