INFO: rcu detected stall in io_uring_enter (2)

Status: upstream: reported on 2026/10/02 21:30
Reported-by: syzbot+ae7d40292e304f02ffd9@syzkaller.appspotmail.com
First crash: 7d15h, last: 7d15h
▶ ▼ Similar bugs (8)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in io_uring_enter fs 1 23 1713d 1841d 0/29 closed as invalid on 2022/02/08 10:00
linux-6.6 INFO: rcu detected stall in io_uring_enter 1 2 243d 314d 0/2 auto-obsoleted due to no activity on 2026/05/20 01:03
upstream INFO: rcu detected stall in io_uring_enter (4) io-uring 1 1 645d 645d 0/29 auto-obsoleted due to no activity on 2025/04/03 10:23
upstream INFO: rcu detected stall in io_uring_enter (2) io-uring 1 1 887d 887d 0/29 auto-obsoleted due to no activity on 2024/08/04 08:24
upstream INFO: rcu detected stall in sys_io_uring_enter (3) mm prio:low 1 59 4d02h 294d 0/29 upstream: reported on 2025/12/19 15:15
upstream INFO: rcu detected stall in io_uring_enter (3) io-uring 1 1 762d 762d 0/29 auto-obsoleted due to no activity on 2024/12/07 05:42
upstream INFO: rcu detected stall in sys_io_uring_enter (2) io-uring 1 37 729d 750d 28/29 fixed on 2024/10/22 11:56
upstream INFO: rcu detected stall in sys_io_uring_enter bpf 1 2 1792d 1802d 0/29 closed as invalid on 2022/02/08 10:00

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-...!: (0 ticks this GP) idle=0f0c/1/0x4000000000000000 softirq=81940/81940 fqs=2
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P17802/3:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=107021, q=164 ncpus=2)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 17801 Comm: syz.4.2951 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
RIP: 0010:hlock_class kernel/locking/lockdep.c:228 [inline]
RIP: 0010:check_wait_context kernel/locking/lockdep.c:4798 [inline]
RIP: 0010:__lock_acquire+0x95a/0x7d80 kernel/locking/lockdep.c:5087
Code: 89 c6 41 81 e6 ff 1f 00 00 c1 e8 03 25 f8 03 00 00 48 8d b8 00 b5 1e 91 be 08 00 00 00 e8 fe 73 77 00 4c 0f a3 35 c6 0f b6 0f <73> 1a 49 69 c6 d0 00 00 00 4c 8d b0 c0 33 b5 90 49 b8 00 00 00 00
RSP: 0018:ffffc90000007880 EFLAGS: 00000057
RAX: 0000000000000001 RBX: 0000000000000001 RCX: ffffffff8168a532
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff911eb508
RBP: ffffc90000007ac8 R08: ffffffff911eb50f R09: 1ffffffff223d6a1
R10: dffffc0000000000 R11: fffffbfff223d6a2 R12: 0000000000000000
R13: ffff88802a4be530 R14: 000000000000006b R15: ffff88802a4be530
FS:  00007fe7f449f6c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f9492f7eeb8 CR3: 00000000483ec000 CR4: 00000000003506f0
DR0: 0000000000000004 DR1: 00000000000001f7 DR2: fffffffffffffffe
DR3: ffffffdfefffff17 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5756
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
 _raw_spin_lock_irqsave+0xb4/0x100 kernel/locking/spinlock.c:162
 debug_object_activate+0x6c/0x500 lib/debugobjects.c:747
 debug_hrtimer_activate kernel/time/hrtimer.c:450 [inline]
 debug_activate kernel/time/hrtimer.c:504 [inline]
 enqueue_hrtimer+0x34/0x380 kernel/time/hrtimer.c:1100
 __run_hrtimer kernel/time/hrtimer.c:1771 [inline]
 __hrtimer_run_queues+0x62f/0xc10 kernel/time/hrtimer.c:1818
 hrtimer_interrupt+0x39d/0x980 kernel/time/hrtimer.c:1880
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1077 [inline]
 __sysvec_apic_timer_interrupt+0xfb/0x3b0 arch/x86/kernel/apic/apic.c:1094
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
 sysvec_apic_timer_interrupt+0x9f/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:__sanitizer_cov_trace_pc+0x57/0x60 kernel/kcov.c:228
Code: 00 74 2c 8b 91 00 16 00 00 83 fa 02 75 21 48 8b 91 08 16 00 00 48 8b 32 48 8d 7e 01 8b 89 04 16 00 00 48 39 cf 73 08 48 89 3a <48> 89 44 f2 08 c3 0f 1f 00 f3 0f 1e fa 48 8b 04 24 65 48 8b 15 40
RSP: 0018:ffffc9001634f620 EFLAGS: 00000283
RAX: ffffffff8432ce47 RBX: 0000000000000100 RCX: 0000000000080000
RDX: ffffc9000bab9000 RSI: 000000000005fc25 RDI: 000000000005fc26
RBP: 0000000000000000 R08: 0000000000001000 R09: 0000000080d5661f
R10: 000000007e13ee64 R11: fffffbfff1d1862e R12: 00000000000006a0
R13: 1ffff1100d01ead5 R14: 0000000000000100 R15: ffff8880680f5000
 __import_iovec+0x2f7/0x850 lib/iov_iter.c:1484
 io_msg_copy_hdr+0x122/0x310 io_uring/net.c:280
 io_sendmsg_copy_hdr+0x181/0x350 io_uring/net.c:312
 io_sendmsg+0x18a/0xba0 io_uring/net.c:427
 io_issue_sqe+0x2c5/0xc60 io_uring/io_uring.c:1869
 io_queue_sqe io_uring/io_uring.c:2053 [inline]
 io_submit_sqe io_uring/io_uring.c:2320 [inline]
 io_submit_sqes+0xa92/0x1d30 io_uring/io_uring.c:2435
 __do_sys_io_uring_enter io_uring/io_uring.c:3779 [inline]
 __se_sys_io_uring_enter+0x318/0x2510 io_uring/io_uring.c:3714
 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: 0033:0x7fe7f359e159
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:00007fe7f449ef38 EFLAGS: 00000246 ORIG_RAX: 00000000000001aa
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fe7f359e159
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000009
RBP: 00000000000000db R08: 0000000000000000 R09: 0000000000000008
R10: 0000000000000000 R11: 0000000000000246 R12: 0000200000000800
R13: 0000200000000808 R14: 00000000000003c9 R15: 0000000000000000
 </TASK>
task:rm              state:R  running task     stack:24360 pid:17802 ppid:17784  flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 preempt_schedule_common+0x82/0xc0 kernel/sched/core.c:6868
 preempt_schedule+0xc0/0xd0 kernel/sched/core.c:6892
 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]
 filemap_map_pages+0x1279/0x19c0 mm/filemap.c:3675
 do_fault_around mm/memory.c:4595 [inline]
 do_read_fault mm/memory.c:4628 [inline]
 do_fault mm/memory.c:4775 [inline]
 do_pte_missing mm/memory.c:3689 [inline]
 handle_pte_fault mm/memory.c:5047 [inline]
 __handle_mm_fault mm/memory.c:5188 [inline]
 handle_mm_fault+0x384b/0x4a50 mm/memory.c:5353
 do_user_addr_fault+0xad2/0x12d0 arch/x86/mm/fault.c:1322
 handle_page_fault arch/x86/mm/fault.c:1463 [inline]
 exc_page_fault+0x64/0x100 arch/x86/mm/fault.c:1516
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:608
RIP: 0033:0x7f94932458f4
RSP: 002b:00007ffe71d64ea8 EFLAGS: 00010283
RAX: 00007f9492f721c8 RBX: 00007f9492f721c8 RCX: 000000000000000b
RDX: 00007f9492f7eeb8 RSI: 00007f949323e580 RDI: ffff806b6d081154
RBP: 00007ffe71d65000 R08: 0000000000000040 R09: 00000000effffef5
R10: 0000000070000029 R11: 00007ffe71d650e8 R12: 0000000000000003
R13: 00007f949323e580 R14: 00007ffe71d650a0 R15: 00007f9492f81000
 </TASK>
rcu: rcu_preempt kthread starved for 10495 jiffies! g107021 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:27848 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 schedule+0xbd/0x170 kernel/sched/core.c:6775
 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:
CPU: 1 PID: 14225 Comm: kworker/u4:2 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
Workqueue: events_unbound toggle_allocation_gate
RIP: 0010:csd_lock_wait kernel/smp.c:311 [inline]
RIP: 0010:smp_call_function_many_cond+0xd98/0x1190 kernel/smp.c:855
Code: e6 01 49 be 00 00 00 00 00 fc ff df 75 07 e8 6f fd 0a 00 eb 38 f3 90 42 0f b6 04 33 84 c0 75 11 41 f7 04 24 01 00 00 00 74 1e <e8> 53 fd 0a 00 eb e4 44 89 e1 80 e1 07 80 c1 03 38 c1 7c e2 4c 89
RSP: 0018:ffffc90004257780 EFLAGS: 00000202
RAX: 0000000000000000 RBX: 1ffff110171c87a5 RCX: ffff8880586f1e00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc90004257900 R08: ffffffff911eb507 R09: 1ffffffff223d6a0
R10: dffffc0000000000 R11: fffffbfff223d6a1 R12: ffff8880b8e43d28
R13: ffff8880b8f3d380 R14: dffffc0000000000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2dd1fff8 CR3: 000000000cf32000 CR4: 00000000003506e0
Call Trace:
 <TASK>
 on_each_cpu_cond_mask+0x3f/0x80 kernel/smp.c:1022
 on_each_cpu include/linux/smp.h:71 [inline]
 text_poke_sync arch/x86/kernel/alternative.c:2222 [inline]
 text_poke_bp_batch+0x31e/0x980 arch/x86/kernel/alternative.c:2432
 text_poke_flush arch/x86/kernel/alternative.c:2623 [inline]
 text_poke_finish+0x30/0x50 arch/x86/kernel/alternative.c:2630
 arch_jump_label_transform_apply+0x1c/0x30 arch/x86/kernel/jump_label.c:146
 static_key_enable_cpuslocked+0x123/0x240 kernel/jump_label.c:207
 static_key_enable+0x1a/0x20 kernel/jump_label.c:220
 toggle_allocation_gate+0xa8/0x260 mm/kfence/core.c:847
 process_one_work kernel/workqueue.c:2657 [inline]
 process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2734
 worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2815
 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>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/02 21:29 linux-6.6.y 79643295eba1 57bbd979 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in io_uring_enter
* Struck through repros no longer work on HEAD.