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INFO: rcu detected stall in futex (2)

Status: upstream: reported C repro on 2025/10/31 01:02
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+aa74f9a1d1d8b3371105@syzkaller.appspotmail.com
First crash: 70d, last: 15h10m
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2025/12/14 linux-6.6.y (ToT) 5fa4793a2d2d C [report] INFO: task hung in perf_event_release_kernel
2025/12/14 upstream (ToT) 8f0b4cce4481 C Didn't crash
▶ ▼ Similar bugs (12)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in sys_futex (7) kernel 1 syz error 101 1h17m 563d 0/29 upstream: reported syz repro on 2024/06/24 16:48
linux-5.15 INFO: rcu detected stall in sys_futex (2) origin:lts-only 1 syz error 55 1d04h 582d 0/3 upstream: reported syz repro on 2024/06/05 16:49
linux-6.6 INFO: rcu detected stall in futex origin:lts-only 1 C done 6 134d 152d 2/2 fixed on 2025/10/06 10:09
upstream INFO: rcu detected stall in futex kvm 1 1 1817d 1817d 0/29 auto-closed as invalid on 2021/04/17 19:46
linux-6.1 INFO: rcu detected stall in sys_futex origin:lts-only 1 syz done 28 2d02h 919d 0/3 upstream: reported syz repro on 2023/07/05 11:35
upstream INFO: rcu detected stall in sys_futex (3) mm 1 959 2193d 2242d 0/29 auto-closed as invalid on 2020/03/08 12:44
upstream INFO: rcu detected stall in sys_futex (2) kernel 1 6 2361d 2505d 0/29 auto-closed as invalid on 2019/10/25 14:11
upstream INFO: rcu detected stall in sys_futex (4) kernel 1 1 1442d 1442d 0/29 closed as invalid on 2022/02/08 10:00
upstream INFO: rcu detected stall in sys_futex kernel 1 1 2566d 2566d 0/29 closed as invalid on 2018/12/31 04:10
linux-5.15 INFO: rcu detected stall in sys_futex 1 4 738d 913d 0/3 auto-obsoleted due to no activity on 2024/04/10 17:08
upstream INFO: rcu detected stall in sys_futex (5) kernel 1 12 1172d 1417d 0/29 auto-obsoleted due to no activity on 2023/02/12 18:33
upstream INFO: rcu detected stall in sys_futex (6) kernel 1 10 741d 977d 0/29 auto-obsoleted due to no activity on 2024/03/29 00:57
▶ ▼ Fix bisection attempts (1)
Created Duration User Patch Repo Result
2025/12/27 09:18 2h32m fix candidate upstream OK (0) job log

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-...!: (0 ticks this GP) idle=9d64/1/0x4000000000000000 softirq=12808/12808 fqs=0
rcu: 	(detected by 1, t=10506 jiffies, g=11373, q=715 ncpus=2)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 5925 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:mark_lock+0x3/0x320 kernel/locking/lockdep.c:4639
Code: 90 48 c7 c7 f0 55 4a 8e e8 9a 49 75 00 4c 89 f7 41 89 d9 e9 79 ff ff ff 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 55 41 57 <41> 56 41 55 41 54 53 50 89 d5 49 89 f6 48 89 fb 49 bd 00 00 00 00
RSP: 0018:ffffc900000078a8 EFLAGS: 00000046
RAX: 0000000000000002 RBX: 0000000000000002 RCX: 0000000000000001
RDX: 0000000000000008 RSI: ffff888023a20ae0 RDI: ffff888023a20000
RBP: ffffc90000007b08 R08: dffffc0000000000 R09: 1ffffffff21b28a0
R10: dffffc0000000000 R11: fffffbfff21b28a1 R12: 0000000000000000
R13: ffff888023a20000 R14: ffff888023a20ae0 R15: ffff888023a20b00
FS:  000055556c591500(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fd7de092f98 CR3: 000000001c71d000 CR4: 00000000003506f0
Call Trace:
 <IRQ>
 mark_usage kernel/locking/lockdep.c:4599 [inline]
 __lock_acquire+0xd49/0x7c80 kernel/locking/lockdep.c:5091
 lock_acquire+0x197/0x410 kernel/locking/lockdep.c:5754
 rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 rcu_read_lock include/linux/rcupdate.h:786 [inline]
 advance_sched+0xa15/0xc80 net/sched/sch_taprio.c:1001
 __run_hrtimer kernel/time/hrtimer.c:1750 [inline]
 __hrtimer_run_queues+0x51e/0xc40 kernel/time/hrtimer.c:1814
 hrtimer_interrupt+0x3c9/0x9c0 kernel/time/hrtimer.c:1876
 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:finish_task_switch+0x26a/0x920 kernel/sched/core.c:5254
Code: 0f 84 37 01 00 00 48 85 db 0f 85 56 01 00 00 0f 1f 44 00 00 4c 8b 75 d0 4c 89 e7 e8 80 ca 14 09 e8 4b a4 2f 00 fb 4c 8b 65 c0 <49> 8d bc 24 f8 15 00 00 48 89 f8 48 c1 e8 03 42 0f b6 04 28 84 c0
RSP: 0018:ffffc90003407898 EFLAGS: 00000282
RAX: f4534085396bc800 RBX: 0000000000000000 RCX: f4534085396bc800
RDX: dffffc0000000000 RSI: ffffffff8aaabce0 RDI: ffffffff8afc6f80
RBP: ffffc900034078f0 R08: ffffffff8e4a212f R09: 1ffffffff1c94425
R10: dffffc0000000000 R11: fffffbfff1c94426 R12: ffff888023a20000
R13: dffffc0000000000 R14: ffff888026cc5a00 R15: ffff8880b8e3cac8
 context_switch kernel/sched/core.c:5383 [inline]
 __schedule+0x14da/0x44d0 kernel/sched/core.c:6699
 schedule+0xbd/0x170 kernel/sched/core.c:6773
 futex_wait_queue+0x138/0x1b0 kernel/futex/waitwake.c:355
 futex_wait+0x19f/0x530 kernel/futex/waitwake.c:656
 do_futex+0x2ff/0x3e0 kernel/futex/syscalls.c:134
 __do_sys_futex kernel/futex/syscalls.c:211 [inline]
 __se_sys_futex+0x36f/0x3f0 kernel/futex/syscalls.c:192
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fd7dd18f749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffee8727d98 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: ffffffffffffffda RBX: 000000000001942d RCX: 00007fd7dd18f749
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007fd7dd3e609c
RBP: 0000000000000032 R08: 0000000000745d1e R09: 0000000ce872808f
R10: 00007ffee8727e90 R11: 0000000000000246 R12: 00007fd7dd3e609c
R13: 00007ffee8727e90 R14: 000000000001945f R15: 00007ffee8727eb0
 </TASK>
rcu: rcu_preempt kthread timer wakeup didn't happen for 10505 jiffies! g11373 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: 	Possible timer handling issue on cpu=0 timer-softirq=5863
rcu: rcu_preempt kthread starved for 10506 jiffies! g11373 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->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:I stack:27752 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5380 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
 schedule+0xbd/0x170 kernel/sched/core.c:6773
 schedule_timeout+0x160/0x280 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x302/0x1560 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x99/0x380 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: 5925 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:debug_objects_fill_pool+0xbc/0x6b0 lib/debugobjects.c:619
Code: 48 83 c4 08 8b 05 34 22 17 09 3b 05 3a 1f 24 0a 7c 4f 48 c7 c7 a0 58 3d 8d 48 89 de e8 ed 43 41 fd 48 c7 44 24 40 0e 36 e0 45 <43> c7 04 2f 00 00 00 00 43 c7 44 2f 14 00 00 00 00 65 48 8b 04 25
RSP: 0018:ffffc90000007b40 EFLAGS: 00000046
RAX: f4534085396bc800 RBX: ffffffff842636a3 RCX: f4534085396bc800
RDX: 0000000000000001 RSI: ffffffff8aaace60 RDI: ffffffff8afc6f80
RBP: ffffc90000007c98 R08: ffffffff8e4a212f R09: 1ffffffff1c94425
R10: dffffc0000000000 R11: fffffbfff1c94426 R12: dffffc0000000000
R13: dffffc0000000000 R14: dffffc0000000000 R15: 1ffff92000000f70
FS:  000055556c591500(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fd7de092f98 CR3: 000000001c71d000 CR4: 00000000003506f0
Call Trace:
 <IRQ>
 debug_object_activate+0x36/0x4b0 lib/debugobjects.c:705
 debug_hrtimer_activate kernel/time/hrtimer.c:450 [inline]
 debug_activate kernel/time/hrtimer.c:505 [inline]
 enqueue_hrtimer+0x30/0x370 kernel/time/hrtimer.c:1108
 __run_hrtimer kernel/time/hrtimer.c:1767 [inline]
 __hrtimer_run_queues+0x637/0xc40 kernel/time/hrtimer.c:1814
 hrtimer_interrupt+0x3c9/0x9c0 kernel/time/hrtimer.c:1876
 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:finish_task_switch+0x26a/0x920 kernel/sched/core.c:5254
Code: 0f 84 37 01 00 00 48 85 db 0f 85 56 01 00 00 0f 1f 44 00 00 4c 8b 75 d0 4c 89 e7 e8 80 ca 14 09 e8 4b a4 2f 00 fb 4c 8b 65 c0 <49> 8d bc 24 f8 15 00 00 48 89 f8 48 c1 e8 03 42 0f b6 04 28 84 c0
RSP: 0018:ffffc90003407898 EFLAGS: 00000282
RAX: f4534085396bc800 RBX: 0000000000000000 RCX: f4534085396bc800
RDX: dffffc0000000000 RSI: ffffffff8aaabce0 RDI: ffffffff8afc6f80
RBP: ffffc900034078f0 R08: ffffffff8e4a212f R09: 1ffffffff1c94425
R10: dffffc0000000000 R11: fffffbfff1c94426 R12: ffff888023a20000
R13: dffffc0000000000 R14: ffff888026cc5a00 R15: ffff8880b8e3cac8
 context_switch kernel/sched/core.c:5383 [inline]
 __schedule+0x14da/0x44d0 kernel/sched/core.c:6699
 schedule+0xbd/0x170 kernel/sched/core.c:6773
 futex_wait_queue+0x138/0x1b0 kernel/futex/waitwake.c:355
 futex_wait+0x19f/0x530 kernel/futex/waitwake.c:656
 do_futex+0x2ff/0x3e0 kernel/futex/syscalls.c:134
 __do_sys_futex kernel/futex/syscalls.c:211 [inline]
 __se_sys_futex+0x36f/0x3f0 kernel/futex/syscalls.c:192
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fd7dd18f749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffee8727d98 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: ffffffffffffffda RBX: 000000000001942d RCX: 00007fd7dd18f749
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007fd7dd3e609c
RBP: 0000000000000032 R08: 0000000000745d1e R09: 0000000ce872808f
R10: 00007ffee8727e90 R11: 0000000000000246 R12: 00007fd7dd3e609c
R13: 00007ffee8727e90 R14: 000000000001945f R15: 00007ffee8727eb0
 </TASK>

Crashes (21):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/01/08 15:47 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-linux-6-6-kasan INFO: rcu detected stall in futex
2025/12/26 17:47 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in futex
2025/12/14 02:06 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in futex
2026/01/08 23:26 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in futex
2026/01/08 20:18 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in futex
2026/01/07 06:56 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in futex
2026/01/05 20:31 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in futex
2025/12/29 18:58 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in futex
2025/12/24 23:30 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in futex
2025/12/22 06:01 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in futex
2025/12/21 17:46 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in futex
2025/12/21 16:52 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in futex
2025/12/13 23:17 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in futex
2025/12/10 02:10 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in futex
2025/12/05 11:56 linux-6.6.y 4791134e4aeb d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in futex
2025/12/03 21:22 linux-6.6.y 4791134e4aeb d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in futex
2025/11/29 16:12 linux-6.6.y 1e89a1be4fe9 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in futex
2025/11/16 13:42 linux-6.6.y 0a805b6ea8cd f7988ea4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in futex
2025/11/11 08:38 linux-6.6.y 0a805b6ea8cd 4e1406b4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in futex
2025/11/04 02:45 linux-6.6.y 0a805b6ea8cd 686bf657 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in futex
2025/10/31 01:02 linux-6.6.y e5bbb12db2c7 2c50b6a9 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in futex
* Struck through repros no longer work on HEAD.