INFO: rcu detected stall in sendfile64

Status: upstream: reported C repro on 2026/06/10 03:23
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+419fa9f4a183b1e48463@syzkaller.appspotmail.com
First crash: 50d, last: 27d
▶ ▼ Bug presence (1)
Date Name Commit Repro Result
2026/07/16 upstream (ToT) 58717b2a1365 C [report] INFO: rcu detected stall in mount
▶ ▼ Similar bugs (17)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 INFO: rcu detected stall in sendfile64 (2) origin:upstream 1 syz, C 4 24d 25d 0/3 upstream: reported C repro on 2026/07/04 16:00
linux-4.14 INFO: rcu detected stall in sendfile64 1 1 2666d 2666d 0/1 auto-closed as invalid on 2019/10/08 13:45
linux-5.15 INFO: rcu detected stall in sendfile64 1 1 264d 264d 0/3 auto-obsoleted due to no activity on 2026/02/15 23:07
linux-4.14 INFO: rcu detected stall in sendfile64 (2) 1 3 2184d 2338d 0/1 auto-closed as invalid on 2020/12/03 20:18
upstream INFO: rcu detected stall in sendfile64 prio:high mm 1 40 25d 165d 0/29 upstream: reported on 2026/02/14 22:22
upstream INFO: rcu detected stall in sys_sendfile64 (3) mm 1 2 1555d 1556d 0/29 auto-closed as invalid on 2022/06/25 08:10
upstream INFO: rcu detected stall in sys_sendfile64 (4) net 1 1 1297d 1297d 0/29 auto-obsoleted due to no activity on 2023/04/18 07:19
upstream INFO: rcu detected stall in sys_sendfile64 (6) fs mm 1 6 642d 803d 0/29 auto-obsoleted due to no activity on 2025/01/24 02:27
linux-5.15 INFO: rcu detected stall in sys_sendfile64 (2) 1 1 617d 617d 0/3 auto-obsoleted due to no activity on 2025/02/27 23:01
upstream INFO: rcu detected stall in sys_sendfile64 lsm 1 syz, C 4 2780d 2779d 0/29 closed as invalid on 2018/12/19 10:12
upstream INFO: rcu detected stall in sys_sendfile64 (2) 1 syz, C done error 100 1666d 2748d 0/29 closed as invalid on 2022/02/08 10:47
linux-4.19 INFO: rcu detected stall in sys_sendfile64 (2) 1 3 2324d 2376d 0/1 auto-closed as invalid on 2020/07/16 06:45
upstream INFO: rcu detected stall in sys_sendfile64 (7) mm 1 1 538d 538d 0/29 auto-obsoleted due to no activity on 2025/05/07 22:38
linux-6.1 INFO: rcu detected stall in sys_sendfile64 1 1 1170d 1170d 0/3 auto-obsoleted due to no activity on 2023/08/24 12:36
upstream INFO: rcu detected stall in sys_sendfile64 (5) fs 1 1 987d 987d 0/29 auto-obsoleted due to no activity on 2024/01/14 10:13
linux-4.19 INFO: rcu detected stall in sys_sendfile64 1 1 2659d 2659d 0/1 auto-closed as invalid on 2019/10/16 04:09
linux-5.15 INFO: rcu detected stall in sys_sendfile64 1 1 734d 734d 0/3 auto-obsoleted due to no activity on 2024/11/03 00:47

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P11/2:b..l
rcu: 	(detected by 0, t=10502 jiffies, g=13529, q=415 ncpus=2)
task:kworker/u4:0    state:R  running task     stack:25032 pid:11    ppid:2      flags:0x00004000
Workqueue: ipv6_addrconf addrconf_dad_work
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6700
 preempt_schedule_common+0x82/0xc0 kernel/sched/core.c:6867
 preempt_schedule+0xc0/0xd0 kernel/sched/core.c:6891
 preempt_schedule_thunk+0x1a/0x30 arch/x86/entry/thunk_64.S:45
 __local_bh_enable_ip+0x14b/0x1c0 kernel/softirq.c:413
 local_bh_enable include/linux/bottom_half.h:33 [inline]
 rcu_read_unlock_bh include/linux/rcupdate.h:856 [inline]
 __dev_queue_xmit+0x1bc2/0x3630 net/core/dev.c:4490
 dev_queue_xmit include/linux/netdevice.h:3113 [inline]
 neigh_hh_output include/net/neighbour.h:527 [inline]
 neigh_output include/net/neighbour.h:541 [inline]
 ip6_finish_output2+0xdf7/0x1620 net/ipv6/ip6_output.c:141
 dst_output include/net/dst.h:467 [inline]
 NF_HOOK+0x167/0x4a0 include/linux/netfilter.h:304
 mld_sendpack+0x802/0xd60 net/ipv6/mcast.c:1823
 ipv6_mc_dad_complete+0x87/0x4b0 net/ipv6/mcast.c:2248
 addrconf_dad_completed+0x77e/0xd90 net/ipv6/addrconf.c:4327
 addrconf_dad_work+0xc9e/0x1550 net/ipv6/addrconf.c:-1
 process_one_work kernel/workqueue.c:2653 [inline]
 process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2730
 worker_thread+0xa5e/0xfe0 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 10532 jiffies! g13529 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:25960 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x15ae/0x4660 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+0x30d/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:
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 6021 Comm: syz.1.18 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:netdev_core_pick_tx+0x11a/0x370 net/core/dev.c:4325
Code: 8b 6d 00 49 83 c5 30 4c 89 e8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df 80 3c 08 00 74 08 4c 89 ef e8 fa 44 67 f9 4d 8b 6d 00 <4d> 85 ed 74 13 e8 7c d0 0e f9 48 89 df 4c 89 f6 4c 89 e2 41 ff d5
RSP: 0018:ffffc900001f0668 EFLAGS: 00000246
RAX: 1ffffffff16a68e2 RBX: ffff88806ca10000 RCX: dffffc0000000000
RDX: ffff88802c6dbc00 RSI: 0000000000000002 RDI: 0000000000000001
RBP: 0000000000000002 R08: dffffc0000000000 R09: 1ffffffff22378ad
R10: dffffc0000000000 R11: fffffbfff22378ae R12: 0000000000000000
R13: 0000000000000000 R14: ffff88801fb0b640 R15: 1ffff1100d942089
FS:  000055557c607500(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000004200 CR3: 000000005f210000 CR4: 00000000003506e0
Call Trace:
 <IRQ>
 __dev_queue_xmit+0x864/0x3630 net/core/dev.c:4410
 dev_queue_xmit include/linux/netdevice.h:3113 [inline]
 hsr_xmit net/hsr/hsr_forward.c:382 [inline]
 hsr_forward_do net/hsr/hsr_forward.c:473 [inline]
 hsr_forward_skb+0x12a9/0x20b0 net/hsr/hsr_forward.c:626
 send_hsr_supervision_frame+0x5fb/0xb90 net/hsr/hsr_device.c:346
 hsr_announce+0x198/0x350 net/hsr/hsr_device.c:402
 call_timer_fn+0x189/0x540 kernel/time/timer.c:1701
 expire_timers kernel/time/timer.c:1752 [inline]
 __run_timers+0x570/0x810 kernel/time/timer.c:2023
 run_timer_softirq+0x67/0xf0 kernel/time/timer.c:2036
 handle_softirqs+0x27d/0x820 kernel/softirq.c:578
 __do_softirq kernel/softirq.c:612 [inline]
 invoke_softirq kernel/softirq.c:452 [inline]
 __irq_exit_rcu+0xd3/0x190 kernel/softirq.c:661
 irq_exit_rcu+0x9/0x20 kernel/softirq.c:673
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
 sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1088
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:in_gate_area_no_mm+0x3d/0x50 arch/x86/entry/vsyscall/vsyscall_64.c:332
Code: 0b bf 02 00 00 00 89 ee e8 00 4d 86 00 83 fd 02 40 0f 95 c5 48 81 e3 00 f0 ff ff 48 c7 c7 00 00 60 ff 48 89 de e8 73 4d 86 00 <48> 81 fb 00 00 60 ff 0f 94 c0 40 20 e8 0f b6 c0 5b 5d c3 f3 0f 1e
RSP: 0018:ffffc900035073b8 EFLAGS: 00000293
RAX: ffffffff81009c1d RBX: 00007fd46899d000 RCX: ffff88802c6dbc00
RDX: 0000000000000000 RSI: 00007fd46899d000 RDI: ffffffffff600000
RBP: 0000000000000001 R08: ffff88802c6dbc00 R09: 0000000000000003
R10: 0000000000000004 R11: 0000000000000000 R12: ffffffff8aa000d0
R13: ffffc90003507840 R14: dffffc0000000000 R15: 1ffff920006a0e8e
 is_kernel_text include/linux/kallsyms.h:31 [inline]
 core_kernel_text kernel/extable.c:68 [inline]
 kernel_text_address+0x2d/0xd0 kernel/extable.c:99
 __kernel_text_address+0xd/0x30 kernel/extable.c:79
 unwind_get_return_address+0x5d/0xc0 arch/x86/kernel/unwind_orc.c:369
 arch_stack_walk+0x11d/0x190 arch/x86/kernel/stacktrace.c:26
 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+0x28/0x40 mm/kasan/generic.c:522
 ____kasan_slab_free+0x126/0x1f0 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+0xba/0x1f0 mm/slub.c:3843
 iter_file_splice_write+0xb36/0xcf0 fs/splice.c:764
 do_splice_from fs/splice.c:933 [inline]
 direct_splice_actor+0xe8/0x130 fs/splice.c:1142
 splice_direct_to_actor+0x30b/0x8e0 fs/splice.c:1088
 do_splice_direct+0x1d5/0x2f0 fs/splice.c:1194
 do_sendfile+0x52b/0xe80 fs/read_write.c:1254
 __do_sys_sendfile64 fs/read_write.c:1322 [inline]
 __se_sys_sendfile64+0x145/0x1a0 fs/read_write.c:1308
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fd46899de59
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:00007fffc47efc68 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007fd468c25fa0 RCX: 00007fd46899de59
RDX: 0000000000000000 RSI: 0000000000000007 RDI: 0000000000000008
RBP: 00007fd468a33e6f R08: 0000000000000000 R09: 0000000000000000
R10: 000000007fffffff R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd468c25fac R14: 00007fd468c25fa0 R15: 00007fd468c25fa0
 </TASK>

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/02 08:35 linux-6.6.y d1cfde2d5d15 27192279 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sendfile64
2026/06/10 03:22 linux-6.6.y 924b4a879cbb 34dab4be .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sendfile64
* Struck through repros no longer work on HEAD.