[syzbot] [mm?] [block?] INFO: rcu detected stall in sendfile64

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: e98f34af6116 Merge tag 'i2c-for-6.19-final' of git://git.k..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14abe7fa580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e3161cabe5a361ff
dashboard link: https://syzkaller.appspot.com/bug?extid=8b65a69dedebce19fd11
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/495818579ef6/disk-e98f34af.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a07da13c17ca/vmlinux-e98f34af.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b38fd29e4a16/bzImage-e98f34af.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8b65a6...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P6857/1:b..l
rcu: (detected by 0, t=10502 jiffies, g=14329, q=377 ncpus=2)
task:syz.2.237 state:R running task stack:26360 pid:6857 tgid:6845 ppid:5832 task_flags:0x400140 flags:0x00080000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5260 [inline]
__schedule+0x1522/0x51d0 kernel/sched/core.c:6867
preempt_schedule_irq+0x4d/0xa0 kernel/sched/core.c:7194
irqentry_exit+0x597/0x620 kernel/entry/common.c:216
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:lock_is_held_type+0x106/0x150 kernel/locking/lockdep.c:5945
Code: 18 00 00 b8 ff ff ff ff 65 0f c1 05 74 f3 5b 07 83 f8 01 75 25 9c 58 a9 00 02 00 00 75 39 41 f7 c4 00 02 00 00 74 01 fb 89 d8 <5b> 41 5c 41 5d 41 5e 41 5f 5d e9 a6 1e 79 f5 cc 90 0f 0b 90 48 c7
RSP: 0018:ffffc900037df408 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000001 RCX: 0000000000000046
RDX: ffff88802afdbd00 RSI: ffffffff8df35112 RDI: ffffffff8c073b00
RBP: 00000000ffffffff R08: ffffea0001dfa1c7 R09: 1ffffd40003bf438
R10: dffffc0000000000 R11: fffff940003bf439 R12: 0000000000000246
R13: ffff88802afdbd00 R14: ffffffff8e55a360 R15: 0000000000000000
xa_entry include/linux/xarray.h:1226 [inline]
xas_next include/linux/xarray.h:1912 [inline]
filemap_get_read_batch+0x642/0x970 mm/filemap.c:2457
filemap_get_pages+0x351/0x1ec0 mm/filemap.c:2680
filemap_splice_read+0x5cd/0xd10 mm/filemap.c:3079
do_splice_read fs/splice.c:982 [inline]
splice_direct_to_actor+0x478/0xc70 fs/splice.c:1086
do_splice_direct_actor fs/splice.c:1204 [inline]
do_splice_direct+0x195/0x290 fs/splice.c:1230
do_sendfile+0x535/0x7d0 fs/read_write.c:1370
__do_sys_sendfile64 fs/read_write.c:1425 [inline]
__se_sys_sendfile64+0xdf/0x1a0 fs/read_write.c:1417
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fd7a899aeb9
RSP: 002b:00007fd7a9835028 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007fd7a8c16180 RCX: 00007fd7a899aeb9
RDX: 0000200000000080 RSI: 0000000000000007 RDI: 0000000000000007
RBP: 00007fd7a8a08c1f R08: 0000000000000000 R09: 0000000000000000
R10: 000000004d9b6eaf R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd7a8c16218 R14: 00007fd7a8c16180 R15: 00007ffc22589c58
</TASK>
rcu: rcu_preempt kthread starved for 10431 jiffies! g14329 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:28000 pid:16 tgid:16 ppid:2 task_flags:0x208040 flags:0x00080000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5260 [inline]
__schedule+0x1522/0x51d0 kernel/sched/core.c:6867
__schedule_loop kernel/sched/core.c:6949 [inline]
schedule+0x164/0x360 kernel/sched/core.c:6964
schedule_timeout+0x158/0x2c0 kernel/time/sleep_timeout.c:99
rcu_gp_fqs_loop+0x312/0x1560 kernel/rcu/tree.c:2083
rcu_gp_kthread+0x9d/0x3b0 kernel/rcu/tree.c:2285
kthread+0x726/0x8b0 kernel/kthread.c:463
ret_from_fork+0x51b/0xa40 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
</TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 0 UID: 0 PID: 6846 Comm: syz.0.238 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
RIP: 0010:csd_lock_wait kernel/smp.c:342 [inline]
RIP: 0010:smp_call_function_many_cond+0xcea/0x1270 kernel/smp.c:877
Code: 89 ee 83 e6 01 31 ff e8 c4 db 0b 00 41 83 e5 01 49 bd 00 00 00 00 00 fc ff df 75 07 e8 6f d7 0b 00 eb 38 f3 90 42 0f b6 04 2b <84> c0 75 11 41 f7 04 24 01 00 00 00 74 1e e8 53 d7 0b 00 eb e4 44
RSP: 0018:ffffc900038cf4a0 EFLAGS: 00000293
RAX: 0000000000000000 RBX: 1ffff110170e8129 RCX: ffff88801aba3d00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc900038cf5c8 R08: ffff8880249a3047 R09: 1ffff11004934608
R10: dffffc0000000000 R11: ffffffff81778480 R12: ffff8880b8740948
R13: dffffc0000000000 R14: ffff8880b863bb00 R15: 0000000000000001
FS: 0000000000000000(0000) GS:ffff8881256f3000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b30b06ff8 CR3: 0000000075c65000 CR4: 0000000000350ef0
Call Trace:
<TASK>
on_each_cpu_cond_mask+0x3f/0x80 kernel/smp.c:1043
__flush_tlb_multi arch/x86/include/asm/paravirt.h:91 [inline]
flush_tlb_multi arch/x86/mm/tlb.c:1382 [inline]
flush_tlb_mm_range+0x5c3/0x10c0 arch/x86/mm/tlb.c:1472
tlb_flush arch/x86/include/asm/tlb.h:23 [inline]
tlb_flush_mmu_tlbonly include/asm-generic/tlb.h:506 [inline]
zap_pte_range mm/memory.c:1885 [inline]
zap_pmd_range mm/memory.c:1950 [inline]
zap_pud_range mm/memory.c:1978 [inline]
zap_p4d_range mm/memory.c:1999 [inline]
unmap_page_range+0x3780/0x4030 mm/memory.c:2020
unmap_single_vma mm/memory.c:2062 [inline]
unmap_vmas+0x3c0/0x5c0 mm/memory.c:2104
exit_mmap+0x251/0xb30 mm/mmap.c:1277
__mmput+0x118/0x430 kernel/fork.c:1173
exit_mm+0x168/0x220 kernel/exit.c:581
do_exit+0x62e/0x2310 kernel/exit.c:959
do_group_exit+0x21b/0x2d0 kernel/exit.c:1112
__do_sys_exit_group kernel/exit.c:1123 [inline]
__se_sys_exit_group kernel/exit.c:1121 [inline]
__x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1121
x64_sys_call+0x2210/0x2210 arch/x86/include/generated/asm/syscalls_64.h:232
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f986059aeb9
Code: Unable to access opcode bytes at 0x7f986059ae8f.
RSP: 002b:00007ffd0f27cf08 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f986059aeb9
RDX: 0000000000000064 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007ffd0f27cf6c R08: 0000000000000000 R09: 00000000000927c0
R10: 0000000000000006 R11: 0000000000000246 R12: 0000000000000023
R13: 00000000000927c0 R14: 000000000003162f R15: 00007ffd0f27cfc0
</TASK>


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