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INFO: rcu detected stall in io_uring_enter

Status: upstream: reported on 2025/11/29 18:08
Reported-by: syzbot+ef7351d16a5f8fa50d49@syzkaller.appspotmail.com
First crash: 78d, last: 6d23h
▶ ▼ Similar bugs (7)
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 1477d 1605d 0/29 closed as invalid on 2022/02/08 10:00
upstream INFO: rcu detected stall in io_uring_enter (4) io-uring 1 1 408d 408d 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 650d 650d 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 1 41 20h32m 58d 0/29 upstream: reported on 2025/12/19 15:15
upstream INFO: rcu detected stall in io_uring_enter (3) io-uring 1 1 525d 525d 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 493d 513d 28/29 fixed on 2024/10/22 11:56
upstream INFO: rcu detected stall in sys_io_uring_enter bpf 1 2 1556d 1565d 0/29 closed as invalid on 2022/02/08 10:00

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P10634/1:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=49797, q=112 ncpus=2)
task:syz.3.1435      state:R  running task     stack:25448 pid:10634 ppid:5765   flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1553/0x45a0 kernel/sched/core.c:6700
 preempt_schedule_irq+0xbf/0x150 kernel/sched/core.c:7010
 irqentry_exit+0x67/0x70 kernel/entry/common.c:438
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:rcu_preempt_read_exit kernel/rcu/tree_plugin.h:386 [inline]
RIP: 0010:__rcu_read_unlock+0x36/0xd0 kernel/rcu/tree_plugin.h:423
Code: 53 49 bf 00 00 00 00 00 fc ff df 65 48 8b 3d 31 0d 92 7e 48 8d 9f 3c 04 00 00 49 89 dc 49 c1 ec 03 43 0f b6 04 3c 84 c0 75 48 <ff> 0b 75 1d 4c 8d b7 40 04 00 00 4c 89 f0 48 c1 e8 03 42 0f b6 04
RSP: 0018:ffffc900037878e0 EFLAGS: 00000246
RAX: 0000000000000000 RBX: ffff8880239dc03c RCX: 4dc58ef64e906d00
RDX: 0000000000000000 RSI: ffffffff8b1c81c0 RDI: ffff8880239dbc00
RBP: ffffffff81de80e0 R08: dffffc0000000000 R09: 1ffffffff2237ea0
R10: dffffc0000000000 R11: fffffbfff2237ea1 R12: 1ffff1100473b807
R13: ffffea0001927c00 R14: 0000000000000007 R15: dffffc0000000000
 rcu_read_unlock include/linux/rcupdate.h:818 [inline]
 percpu_ref_get_many include/linux/percpu-refcount.h:209 [inline]
 percpu_ref_get include/linux/percpu-refcount.h:222 [inline]
 obj_cgroup_get include/linux/memcontrol.h:798 [inline]
 memcg_slab_post_alloc_hook mm/slab.h:542 [inline]
 slab_post_alloc_hook+0x2da/0x4b0 mm/slab.h:775
 kmem_cache_alloc_bulk+0x452/0x5a0 mm/slub.c:4077
 __io_alloc_req_refill+0x278/0x4b0 io_uring/io_uring.c:1099
 io_alloc_req io_uring/io_uring.h:379 [inline]
 io_submit_sqes+0xc9e/0x1d00 io_uring/io_uring.c:2424
 __do_sys_io_uring_enter io_uring/io_uring.c:3779 [inline]
 __se_sys_io_uring_enter+0x315/0x2540 io_uring/io_uring.c:3714
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fa6b059aeb9
RSP: 002b:00007fa6b144a028 EFLAGS: 00000246 ORIG_RAX: 00000000000001aa
RAX: ffffffffffffffda RBX: 00007fa6b0816090 RCX: 00007fa6b059aeb9
RDX: 0000000000000483 RSI: 0000000000003516 RDI: 0000000000000005
RBP: 00007fa6b0608c1f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa6b0816128 R14: 00007fa6b0816090 R15: 00007fff20bfa358
 </TASK>
rcu: rcu_preempt kthread starved for 10390 jiffies! g49797 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:27656 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1553/0x45a0 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+0x313/0x1590 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 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 0 Comm: swapper/0 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
RIP: 0010:pv_native_safe_halt+0xf/0x10 arch/x86/kernel/paravirt.c:148
Code: e7 22 02 c3 cc cc cc cc cc cc cc f3 0f 1e fa 0f 0b 66 2e 0f 1f 84 00 00 00 00 00 f3 0f 1e fa 66 90 0f 00 2d 83 f1 43 00 fb f4 <c3> 66 0f 1f 00 55 41 57 41 56 41 54 53 50 8b 2f eb 2e 41 89 de 80
RSP: 0018:ffffffff8ce07d80 EFLAGS: 000002c2
RAX: 7be13fbc9bd17a00 RBX: ffffffff8162a490 RCX: 7be13fbc9bd17a00
RDX: 0000000000000001 RSI: ffffffff8acac900 RDI: ffffffff8b1c81e0
RBP: ffffffff8ce07eb8 R08: ffff8880b8e36b2b R09: 1ffff110171c6d65
R10: dffffc0000000000 R11: ffffed10171c6d66 R12: 1ffffffff19d2688
R13: 1ffffffff19c0fbc R14: 0000000000000000 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055717c3e3a38 CR3: 0000000025a66000 CR4: 00000000003506f0
Call Trace:
 <TASK>
 arch_safe_halt arch/x86/include/asm/paravirt.h:108 [inline]
 default_idle+0x13/0x20 arch/x86/kernel/process.c:753
 default_idle_call+0x6c/0xa0 kernel/sched/idle.c:97
 cpuidle_idle_call kernel/sched/idle.c:170 [inline]
 do_idle+0x1f0/0x4e0 kernel/sched/idle.c:282
 cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:380
 rest_init+0x2e2/0x300 init/main.c:744
 arch_call_rest_init+0xe/0x10 init/main.c:841
 start_kernel+0x459/0x4e0 init/main.c:1086
 x86_64_start_reservations+0x2a/0x30 arch/x86/kernel/head64.c:555
 x86_64_start_kernel+0x60/0x60 arch/x86/kernel/head64.c:536
 secondary_startup_64_no_verify+0x179/0x17b
 </TASK>

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/02/09 01:03 linux-6.6.y c56aaf1a85ae 4c131dc4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in io_uring_enter
2025/11/29 18:07 linux-6.6.y 1e89a1be4fe9 d6526ea3 .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.