INFO: rcu detected stall in call_timer_fn

Status: upstream: reported on 2025/09/20 00:57
Reported-by: syzbot+c4956fba553abbcc9f30@syzkaller.appspotmail.com
First crash: 384d, last: 12d
▶ ▼ Similar bugs (15)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream BUG: soft lockup in call_timer_fn net mm 1 19 801d 843d 0/29 auto-obsoleted due to no activity on 2024/10/08 10:43
linux-6.1 INFO: rcu detected stall in call_timer_fn 1 2 726d 798d 0/3 auto-obsoleted due to no activity on 2025/01/21 02:15
linux-4.19 INFO: rcu detected stall in call_timer_fn (2) 1 16 2165d 2439d 0/1 auto-closed as invalid on 2021/03/04 12:30
upstream INFO: rcu detected stall in call_timer_fn (5) net input usb 1 syz, C 9 456d 589d 0/29 upstream: reported C repro on 2025/02/27 04:11
linux-4.14 INFO: rcu detected stall in call_timer_fn (2) 1 1 2227d 2227d 0/1 auto-closed as invalid on 2020/12/31 22:00
upstream INFO: rcu detected stall in call_timer_fn (2) kernel 1 syz, C done error 47 1724d 2580d 0/29 closed as invalid on 2022/02/08 10:46
upstream INFO: rcu detected stall in call_timer_fn bpf net 1 2 2918d 2930d 0/29 closed as dup on 2019/01/02 16:26
linux-4.19 INFO: rcu detected stall in call_timer_fn 1 1 2578d 2578d 0/1 auto-closed as invalid on 2020/01/15 18:43
linux-6.1 INFO: rcu detected stall in call_timer_fn (2) 1 2 221d 242d 0/3 auto-obsoleted due to no activity on 2026/06/09 18:18
linux-4.14 INFO: rcu detected stall in call_timer_fn 1 5 2352d 2471d 0/1 auto-closed as invalid on 2020/08/29 09:07
upstream INFO: rcu detected stall in call_timer_fn (4) mm 1 1 982d 982d 0/29 auto-obsoleted due to no activity on 2024/03/31 10:44
upstream INFO: rcu detected stall in call_timer_fn (3) kernel 1 3 1463d 1479d 0/29 auto-obsoleted due to no activity on 2023/01/12 18:45
linux-6.1 INFO: rcu detected stall in call_timer_fn (3) 1 2 77d 90d 0/3 upstream: reported on 2026/07/10 22:14
linux-4.19 BUG: soft lockup in call_timer_fn 1 syz, C error 31 1314d 1917d 0/1 upstream: reported C repro on 2021/07/10 02:48
upstream BUG: soft lockup in call_timer_fn (2) trace 1 1 727d 723d 0/29 auto-obsoleted due to no activity on 2025/01/10 05:15

Sample crash report:
rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	0-...!: (10499 ticks this GP) idle=211/1/0x4000000000000000 softirq=19213/19213 fqs=26 
	(t=10501 jiffies g=25933 q=523)
rcu: rcu_preempt kthread starved for 10450 jiffies! g25933 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:27920 pid:   15 ppid:     2 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5049 [inline]
 __schedule+0x11c3/0x4350 kernel/sched/core.c:6395
 schedule+0x11b/0x1e0 kernel/sched/core.c:6478
 schedule_timeout+0x184/0x2d0 kernel/time/timer.c:2117
 rcu_gp_fqs_loop+0x2be/0x11f0 kernel/rcu/tree.c:1972
 rcu_gp_kthread+0x9a/0x370 kernel/rcu/tree.c:2145
 kthread+0x42e/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </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: 8338 Comm: syz.3.857 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:pv_wait_head_or_lock kernel/locking/qspinlock_paravirt.h:434 [inline]
RIP: 0010:__pv_queued_spin_lock_slowpath+0x520/0x9b0 kernel/locking/qspinlock.c:508
Code: 8b 44 24 18 c6 00 00 48 8b 44 24 10 42 0f b6 04 28 84 c0 0f 85 1c 01 00 00 48 8d 43 01 c6 00 01 41 bc 00 80 ff ff eb 07 f3 90 <41> ff c4 74 47 43 0f b6 04 2e 84 c0 75 2b 80 3b 00 75 eb 48 89 df
RSP: 0018:ffffc900035ffc20 EFLAGS: 00000206
RAX: 0000000000000000 RBX: ffff888016e36dc0 RCX: ffdd696f11367d00
RDX: dffffc0000000000 RSI: ffffffff8a2b2be0 RDI: ffffffff8a7a48c0
RBP: ffffc900035ffd18 R08: ffffffff901f10df R09: 1ffffffff203e21b
R10: dffffc0000000000 R11: fffffbfff203e21c R12: 00000000ffffb0a7
R13: dffffc0000000000 R14: 1ffff11002dc6db8 R15: ffff8880b9130001
FS:  00007f2c14b426c0(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2c14b41ff8 CR3: 00000000392ff000 CR4: 00000000003506e0
DR0: 0000200000000300 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <TASK>
 pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:585 [inline]
 queued_spin_lock_slowpath+0x43/0x50 arch/x86/include/asm/qspinlock.h:51
 queued_spin_lock include/asm-generic/qspinlock.h:85 [inline]
 do_raw_spin_lock+0x265/0x2f0 kernel/locking/spinlock_debug.c:115
 spin_lock include/linux/spinlock.h:364 [inline]
 alloc_fd+0x62/0x650 fs/file.c:486
 __sys_socketpair+0x64/0x540 net/socket.c:1629
 __do_sys_socketpair net/socket.c:1705 [inline]
 __se_sys_socketpair net/socket.c:1702 [inline]
 __x64_sys_socketpair+0x97/0xb0 net/socket.c:1702
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f2c1692c159
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:00007f2c14b42028 EFLAGS: 00000246 ORIG_RAX: 0000000000000035
RAX: ffffffffffffffda RBX: 00007f2c16bb4180 RCX: 00007f2c1692c159
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000001
RBP: 00007f2c169c306b R08: 0000000000000000 R09: 0000000000000000
R10: 00002000000004c0 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2c16bb4218 R14: 00007f2c16bb4180 R15: 00007ffe8ccce238
 </TASK>
NMI backtrace for cpu 0
CPU: 0 PID: 8322 Comm: syz.3.857 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <IRQ>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x3a2/0x3d0 lib/nmi_backtrace.c:111
 nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62
 trigger_single_cpu_backtrace include/linux/nmi.h:166 [inline]
 rcu_dump_cpu_stacks+0x22d/0x380 kernel/rcu/tree_stall.h:349
 print_cpu_stall+0x31f/0x5f0 kernel/rcu/tree_stall.h:633
 check_cpu_stall kernel/rcu/tree_stall.h:727 [inline]
 rcu_pending kernel/rcu/tree.c:3936 [inline]
 rcu_sched_clock_irq+0x6ec/0x1120 kernel/rcu/tree.c:2619
 update_process_times+0x193/0x200 kernel/time/timer.c:2021
 tick_sched_handle kernel/time/tick-sched.c:254 [inline]
 tick_sched_timer+0x37d/0x560 kernel/time/tick-sched.c:1473
 __run_hrtimer kernel/time/hrtimer.c:1685 [inline]
 __hrtimer_run_queues+0x4b0/0xb60 kernel/time/hrtimer.c:1749
 hrtimer_interrupt+0x397/0x8b0 kernel/time/hrtimer.c:1811
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1097 [inline]
 __sysvec_apic_timer_interrupt+0x137/0x4a0 arch/x86/kernel/apic/apic.c:1114
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0x4d/0xc0 arch/x86/kernel/apic/apic.c:1108
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xbc/0x120 kernel/locking/spinlock.c:194
Code: c7 44 24 20 00 00 00 00 9c 8f 44 24 20 f7 44 24 20 00 02 00 00 41 c6 04 07 f8 75 4b f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> 3f b1 87 f7 65 8b 05 70 c7 37 76 85 c0 74 3c 48 c7 04 24 0e 36
RSP: 0018:ffffc900000079c0 EFLAGS: 00000206
RAX: dffffc0000000004 RBX: 0000000000000a02 RCX: 5c96d81bf2081300
RDX: dffffc0000000000 RSI: ffffffff8a2b2be0 RDI: 0000000000000001
RBP: ffffc90000007a58 R08: ffffffff901f115f R09: 1ffffffff203e22b
R10: dffffc0000000000 R11: fffffbfff203e22c R12: dffffc0000000000
R13: ffff88814c0fb8f8 R14: ffffffff965bddc8 R15: 1ffff92000000f38
 debug_object_assert_init+0x1e8/0x2f0 lib/debugobjects.c:891
 debug_timer_assert_init kernel/time/timer.c:739 [inline]
 debug_assert_init kernel/time/timer.c:784 [inline]
 __mod_timer+0x55/0xd20 kernel/time/timer.c:967
 call_timer_fn+0x17b/0x540 kernel/time/timer.c:1648
 expire_timers kernel/time/timer.c:1699 [inline]
 __run_timers+0x56c/0x810 kernel/time/timer.c:1970
 run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1983
 handle_softirqs+0x336/0x830 kernel/softirq.c:576
 __do_softirq kernel/softirq.c:610 [inline]
 invoke_softirq kernel/softirq.c:450 [inline]
 __irq_exit_rcu+0x13b/0x230 kernel/softirq.c:659
 irq_exit_rcu+0x5/0x20 kernel/softirq.c:671
 instr_sysvec_irq_work arch/x86/kernel/irq_work.c:17 [inline]
 sysvec_irq_work+0x9d/0xc0 arch/x86/kernel/irq_work.c:17
 </IRQ>
 <TASK>
 asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:713
RIP: 0010:_find_next_bit+0x72/0x200 lib/find_bit.c:-1
Code: df 4d 89 fc 49 c1 ec 06 48 89 6c 24 18 4e 8d 74 e5 00 4c 89 f0 48 c1 e8 03 80 3c 08 00 74 08 4c 89 f7 e8 81 54 d6 fd 49 8b 2e <4c> 8b 34 24 4d 85 f6 74 2d e8 b0 20 91 fd 4f 8d 34 e6 4c 89 f0 48
RSP: 0018:ffffc900035efdb0 EFLAGS: 00000246
RAX: 1ffff1100fc5fd38 RBX: 0000000000000004 RCX: dffffc0000000000
RDX: 0000000000000002 RSI: 0000000000000004 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffffffffffffffff R09: 0000000000000000
R10: dffffc0000000000 R11: fffff520006bdfb0 R12: 0000000000000000
R13: ffffffffffffffff R14: ffff88807e2fe9c0 R15: 0000000000000000
 find_next_zero_bit include/asm-generic/bitops/find.h:94 [inline]
 find_next_fd fs/file.c:468 [inline]
 alloc_fd+0x1a2/0x650 fs/file.c:494
 __sys_socketpair+0x64/0x540 net/socket.c:1629
 __do_sys_socketpair net/socket.c:1705 [inline]
 __se_sys_socketpair net/socket.c:1702 [inline]
 __x64_sys_socketpair+0x97/0xb0 net/socket.c:1702
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f2c1692c159
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:00007f2c14b84028 EFLAGS: 00000246 ORIG_RAX: 0000000000000035
RAX: ffffffffffffffda RBX: 00007f2c16bb3fa0 RCX: 00007f2c1692c159
RDX: 0000000000000000 RSI: 0000000000000002 RDI: 0000000000000001
RBP: 00007f2c169c306b R08: 0000000000000000 R09: 0000000000000000
R10: 00002000000001c0 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2c16bb4038 R14: 00007f2c16bb3fa0 R15: 00007ffe8ccce238
 </TASK>

Crashes (12):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/27 06:20 linux-5.15.y 0248c33e835e a3c7249d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in call_timer_fn
2026/09/23 04:19 linux-5.15.y 0248c33e835e 5207b90e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in call_timer_fn
2026/07/16 19:44 linux-5.15.y c86c4726e7f0 71b49442 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in call_timer_fn
2026/07/02 10:03 linux-5.15.y eceeec79dbc6 27192279 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in call_timer_fn
2026/06/07 20:23 linux-5.15.y dc027a595035 cc095639 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in call_timer_fn
2026/03/18 20:54 linux-5.15.y 91d48252ad4b 0199f9a1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in call_timer_fn
2026/02/25 21:08 linux-5.15.y 3330a8d33e08 94a9671e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in call_timer_fn
2026/01/25 11:13 linux-5.15.y 9eec9a14ee10 40acda8a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in call_timer_fn
2025/11/30 15:21 linux-5.15.y cc5ec8769306 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in call_timer_fn
2025/11/30 11:57 linux-5.15.y cc5ec8769306 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in call_timer_fn
2025/10/23 14:22 linux-5.15.y ac56c046adf4 c0460fcd .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in call_timer_fn
2025/09/20 00:57 linux-5.15.y 43bb85222e53 67c37560 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in call_timer_fn
* Struck through repros no longer work on HEAD.