syzbot


INFO: rcu detected stall in sys_futex

Status: upstream: reported C repro on 2023/07/05 11:35
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+97f2ac670e5e7a3b48e4@syzkaller.appspotmail.com
First crash: 1029d, last: 19d
Fix commit to backport (bisect log) :
tree: upstream
commit f4bf3ca2e5cba655824b6e0893a98dfb33ed24e5
Author: Lingutla Chandrasekhar <clingutla@codeaurora.org>
Date: Fri Apr 7 23:05:26 2023 +0000

  softirq: Add trace points for tasklet entry/exit

[report pending]
  
Discussions (2)
Title Replies (including bot) Last reply
Re: [PATCH 6.1] softirq: Add trace points for tasklet entry/exit 3 (3) 2025/08/21 22:05
[PATCH 6.1] softirq: Add trace points for tasklet entry/exit 1 (1) 2025/08/21 18:40
Bug presence (2)
Date Name Commit Repro Result
2026/04/10 linux-6.1.y (ToT) 1989cd3d56e2 C [report] INFO: rcu detected stall in corrupted
2026/04/10 upstream (ToT) 9a9c8ce300cd C Didn't crash
Similar bugs (12)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.6 INFO: rcu detected stall in futex (2) origin:lts-only 1 C inconclusive 44 16d 180d 0/2 upstream: reported C repro on 2025/10/31 01:02
upstream INFO: rcu detected stall in sys_futex (7) kernel 1 syz error error 110 3d03h 674d 0/29 upstream: reported syz repro on 2024/06/24 16:48
upstream INFO: rcu detected stall in sys_futex (3) mm 1 959 2303d 2352d 0/29 auto-closed as invalid on 2020/03/08 12:44
upstream INFO: rcu detected stall in sys_futex (2) kernel 1 6 2471d 2615d 0/29 auto-closed as invalid on 2019/10/25 14:11
upstream INFO: rcu detected stall in sys_futex (4) kernel 1 1 1552d 1552d 0/29 closed as invalid on 2022/02/08 10:00
linux-5.15 INFO: rcu detected stall in sys_futex (2) origin:lts-only 1 syz error 74 8d09h 693d 0/3 upstream: reported syz repro on 2024/06/05 16:49
upstream INFO: rcu detected stall in sys_futex kernel 1 1 2677d 2677d 0/29 closed as invalid on 2018/12/31 04:10
linux-6.6 INFO: rcu detected stall in futex origin:lts-only 1 C done 6 245d 262d 2/2 fixed on 2025/10/06 10:09
linux-5.15 INFO: rcu detected stall in sys_futex 1 4 849d 1023d 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 1283d 1528d 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 851d 1087d 0/29 auto-obsoleted due to no activity on 2024/03/29 00:57
upstream INFO: rcu detected stall in futex kvm 1 1 1928d 1928d 0/29 auto-closed as invalid on 2021/04/17 19:46
Last patch testing requests (1)
Created Duration User Patch Repo Result
2025/08/12 15:54 25m sumanth.gavini@yahoo.com patch linux-6.1.y OK log
Fix bisection attempts (1)
Created Duration User Patch Repo Result
2025/04/07 17:31 7h36m fix candidate upstream OK (1) job log

Sample crash report:
rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 1-.... } 2630 jiffies s: 27637 root: 0x2/.
rcu: blocking rcu_node structures (internal RCU debug):
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 18418 Comm: syz.1.6409 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
RIP: 0010:check_kcov_mode kernel/kcov.c:182 [inline]
RIP: 0010:write_comp_data kernel/kcov.c:245 [inline]
RIP: 0010:__sanitizer_cov_trace_const_cmp8+0x2a/0x80 kernel/kcov.c:320
Code: 48 8b 04 24 65 48 8b 0d c4 f6 7f 7e 65 8b 15 c5 f6 7f 7e 81 e2 00 01 ff 00 74 11 81 fa 00 01 00 00 75 57 83 b9 1c 16 00 00 00 <74> 4e 8b 91 f8 15 00 00 83 fa 03 75 43 48 8b 91 00 16 00 00 44 8b
RSP: 0018:ffffc900001e01b8 EFLAGS: 00000046
RAX: ffffffff813a0f35 RBX: 00000000b8f3b9f0 RCX: ffff88802ababb80
RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000001 R08: ffff8880b8f3b9fb R09: 1ffff110171e773f
R10: dffffc0000000000 R11: ffffed10171e7740 R12: 0000000000000000
R13: dffffc0000000001 R14: 000000000000002e R15: 0000000000000000
FS:  00007f39a6c7a6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000037079fec9000 CR3: 000000007d690000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 phys_addr_valid arch/x86/mm/physaddr.h:7 [inline]
 __virt_addr_valid+0xb5/0x540 arch/x86/mm/physaddr.c:61
 kasan_addr_to_slab+0x9/0xc0 mm/kasan/common.c:36
 __kasan_record_aux_stack+0xf/0xc0 mm/kasan/generic.c:471
 irq_work_queue_on+0x10f/0x260 kernel/irq_work.c:140
 rcu_read_unlock_special+0x3c9/0x510 kernel/rcu/tree_plugin.h:678
 __rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:426
 rcu_read_unlock include/linux/rcupdate.h:823 [inline]
 __perf_event_output kernel/events/core.c:7741 [inline]
 perf_event_output_forward+0x271/0x2f0 kernel/events/core.c:7750
 __perf_event_overflow+0x448/0x610 kernel/events/core.c:9496
 perf_swevent_overflow kernel/events/core.c:9579 [inline]
 perf_swevent_event+0x315/0x570 kernel/events/core.c:9630
 perf_tp_event+0x3e7/0xc30 kernel/events/core.c:10064
 perf_trace_run_bpf_submit+0xf3/0x1c0 kernel/events/core.c:10032
 perf_trace_preemptirq_template+0x268/0x320 include/trace/events/preemptirq.h:14
 trace_irq_enable_rcuidle+0xd3/0x140 include/trace/events/preemptirq.h:40
 trace_hardirqs_on+0x24/0x40 kernel/trace/trace_preemptirq.c:44
 asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:728
RIP: 0010:rcu_read_unlock_special+0x7f/0x510 kernel/rcu/tree_plugin.h:685
Code: eb 03 48 b8 f1 f1 f1 f1 f8 f2 f2 f2 4a 89 04 2b 42 c7 44 2b 08 f8 f3 f3 f3 65 44 8b 35 d2 33 95 7e 41 f7 c6 00 00 f0 00 74 40 <48> c7 44 24 40 0e 36 e0 45 4a c7 04 2b 00 00 00 00 42 c7 44 2b 08
RSP: 0018:ffffc900001e0ac0 EFLAGS: 00000206
RAX: 6f28316e77106700 RBX: 1ffff9200003c160 RCX: 6f28316e77106700
RDX: dffffc0000000000 RSI: ffffffff8a8c10a0 RDI: ffffffff8adf0d20
RBP: ffffc900001e0bc0 R08: ffff8880b8f3580b R09: 1ffff110171e6b01
R10: dffffc0000000000 R11: ffffed10171e6b02 R12: 0000000000000246
R13: dffffc0000000000 R14: ffff8880b8f3b900 R15: 0000000000000002
 __rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:426
 rcu_read_unlock include/linux/rcupdate.h:823 [inline]
 ieee80211_rx_napi+0x221/0x3d0 net/mac80211/rx.c:5339
 ieee80211_rx include/net/mac80211.h:4849 [inline]
 ieee80211_handle_queued_frames+0x105/0x1b0 net/mac80211/main.c:317
 tasklet_action_common+0x2fe/0x4d0 kernel/softirq.c:827
 handle_softirqs+0x2a1/0x930 kernel/softirq.c:596
 __do_softirq kernel/softirq.c:630 [inline]
 invoke_softirq kernel/softirq.c:470 [inline]
 __irq_exit_rcu+0x13b/0x230 kernel/softirq.c:679
 irq_exit_rcu+0x5/0x20 kernel/softirq.c:691
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
 sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1118
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:finish_task_switch+0x26a/0x8f0 kernel/sched/core.c:5124
Code: 0f 84 3b 01 00 00 48 85 db 0f 85 5a 01 00 00 0f 1f 44 00 00 4c 8b 75 d0 4c 89 e7 e8 00 2c de 08 e8 8b 2c 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:ffffc900048ef8f8 EFLAGS: 00000282
RAX: 6f28316e77106700 RBX: 0000000000000000 RCX: 6f28316e77106700
RDX: dffffc0000000000 RSI: ffffffff8a8c10a0 RDI: ffffffff8adf0d20
RBP: ffffc900048ef950 R08: ffff8880b8f3580b R09: 1ffff110171e6b01
R10: dffffc0000000000 R11: ffffed10171e6b02 R12: ffff88802ababb80
R13: dffffc0000000000 R14: ffff88802e5c9dc0 R15: ffff8880b8f3b5d0
 context_switch kernel/sched/core.c:5248 [inline]
 __schedule+0x11d9/0x40e0 kernel/sched/core.c:6562
 schedule+0xb9/0x180 kernel/sched/core.c:6638
 futex_wait_queue+0x134/0x1b0 kernel/futex/waitwake.c:355
 futex_wait+0x1e8/0x5e0 kernel/futex/waitwake.c:656
 do_futex+0x310/0x320 kernel/futex/syscalls.c:134
 __do_sys_futex kernel/futex/syscalls.c:211 [inline]
 __se_sys_futex+0x381/0x410 kernel/futex/syscalls.c:192
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f39a5d9c819
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:00007f39a6c7a0e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: ffffffffffffffda RBX: 00007f39a6015fa8 RCX: 00007f39a5d9c819
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f39a6015fa8
RBP: 00007f39a6015fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f39a6016038 R14: 00007ffdbedf94a0 R15: 00007ffdbedf9588
 </TASK>

Crashes (36):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/04/09 23:33 linux-6.1.y 1989cd3d56e2 38c8e246 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in futex
2025/03/14 09:30 linux-6.1.y 344a09659766 e2826670 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in sys_futex
2026/04/01 19:49 linux-6.1.y 1989cd3d56e2 9a1f7828 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in futex
2026/02/08 04:32 linux-6.1.y 0182cb5b74ee 4c131dc4 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in futex
2025/09/20 04:03 linux-6.1.y 363a599da6d9 67c37560 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in futex
2025/01/08 10:23 linux-6.1.y 7dc732d24ff7 f3558dbf .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_futex
2024/10/14 09:18 linux-6.1.y aa4cd140bba5 084d8178 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in sys_futex
2024/10/01 18:17 linux-6.1.y aa4cd140bba5 ea2b66a6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in sys_futex
2024/09/02 03:20 linux-6.1.y 311d8503ef9f 1eda0d14 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in sys_futex
2024/08/05 06:08 linux-6.1.y 48d525b0e463 1786a2a8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in sys_futex
2024/06/19 18:49 linux-6.1.y eb44d83053d6 41b7e219 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_futex
2024/06/11 01:38 linux-6.1.y 88690811da69 048c640a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_futex
2024/06/08 12:33 linux-6.1.y 88690811da69 82c05ab8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_futex
2024/06/07 10:14 linux-6.1.y 88690811da69 121701b6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_futex
2024/06/06 13:57 linux-6.1.y 88690811da69 121701b6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_futex
2024/05/09 12:07 linux-6.1.y 909ba1f1b414 05079661 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_futex
2024/05/05 09:10 linux-6.1.y 909ba1f1b414 610f2a54 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in sys_futex
2024/03/28 15:11 linux-6.1.y e5cd595e23c1 e91187ee .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_futex
2024/01/09 19:35 linux-6.1.y 38fb82ecd144 4807fb37 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_futex
2023/10/04 13:29 linux-6.1.y d23900f974e0 b7d7ff54 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_futex
2023/07/14 08:34 linux-6.1.y 61fd484b2cf6 d624500f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_futex
2023/07/05 11:34 linux-6.1.y 0f4ac6b4c5f0 80298b6f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_futex
2026/04/09 20:21 linux-6.1.y 1989cd3d56e2 38c8e246 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in futex
2026/03/31 06:41 linux-6.1.y 1989cd3d56e2 d0af506e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in futex
2026/03/08 05:25 linux-6.1.y f2ddafa93a25 5cb44a80 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in futex
2026/02/28 20:34 linux-6.1.y 779f9571ac3e 43249bac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in futex
2026/02/23 09:40 linux-6.1.y 779f9571ac3e 6e7b5511 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in futex
2026/01/07 12:28 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in futex
2025/11/26 04:27 linux-6.1.y f6e38ae624cf 64219f15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in futex
2025/11/08 07:25 linux-6.1.y f6e38ae624cf 4e1406b4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in futex
2025/10/31 11:37 linux-6.1.y f6e38ae624cf 2c50b6a9 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in futex
2025/10/16 04:02 linux-6.1.y c2fda4b3f577 19568248 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in futex
2025/10/08 16:56 linux-6.1.y 882efbdd9d34 7e2882b3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in futex
2025/09/22 09:22 linux-6.1.y 363a599da6d9 67c37560 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in futex
2025/09/19 01:34 linux-6.1.y 3db754f56897 e2beed91 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in futex
2025/05/06 00:13 linux-6.1.y ac7079a42ea5 6ca47dd8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in futex
* Struck through repros no longer work on HEAD.