INFO: rcu detected stall in task_work_run (3)

Status: upstream: reported syz repro on 2025/09/13 23:38
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+746695ac27c8f3020623@syzkaller.appspotmail.com
First crash: 354d, last: 2d17h
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2025/09/16 linux-5.15.y (ToT) 43bb85222e53 syz [report] INFO: rcu detected stall in corrupted
2025/09/16 upstream (ToT) 46a51f4f5eda syz Didn't crash
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 INFO: rcu detected stall in task_work_run origin:lts-only 1 syz, C error 4 2d20h 364d 0/3 upstream: reported C repro on 2025/09/04 00:43
linux-5.15 INFO: rcu detected stall in task_work_run (2) origin:lts-only 1 syz error 1 640d 640d 0/3 auto-obsoleted due to no activity on 2025/03/24 21:44
linux-5.15 INFO: rcu detected stall in task_work_run 1 1 891d 891d 0/3 auto-obsoleted due to no activity on 2024/07/04 00:01
upstream INFO: rcu detected stall in task_work_run kernel 1 2 1120d 1170d 0/29 auto-obsoleted due to no activity on 2023/11/07 12:15
linux-6.6 INFO: rcu detected stall in task_work_run 1 1 9d20h 9d20h 0/2 upstream: reported on 2026/08/24 04:09
▶ ▼ Last patch testing requests (10)
Created Duration User Patch Repo Result
2026/07/30 21:29 19m retest repro linux-5.15.y report log
2026/07/30 21:29 19m retest repro linux-5.15.y report log
2026/07/30 21:29 30m retest repro linux-5.15.y report log
2026/06/12 12:33 19m retest repro linux-5.15.y report log
2026/05/17 02:38 20m retest repro linux-5.15.y report log
2026/05/17 02:38 28m retest repro linux-5.15.y report log
2026/05/17 02:38 19m retest repro linux-5.15.y report log
2026/04/01 09:14 17m retest repro linux-5.15.y report log
2026/04/01 09:05 14m retest repro linux-5.15.y report log
2026/03/07 10:58 12m retest repro linux-5.15.y report log
▶ ▼ Fix bisection attempts (7)
Created Duration User Patch Repo Result
2026/05/23 18:48 19m fix candidate upstream error job log
2026/03/24 15:25 1m fix candidate upstream error job log
2026/02/22 07:57 1m fix candidate upstream error job log
2026/01/23 05:34 5m fix candidate upstream error job log
2025/12/21 07:18 16m fix candidate upstream error job log
2025/11/14 04:11 58m fix candidate upstream error job log
2025/10/18 02:26 32m bisect fix linux-5.15.y error job log

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-....: (1 GPs behind) idle=f49/1/0x4000000000000002 softirq=17697/17698 fqs=2098 
	(detected by 1, t=10504 jiffies, g=28297, q=262379)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 6880 Comm: syz.1.2465 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:perf_trace_preemptirq_template+0x2f5/0x360 include/trace/events/preemptirq.h:14
Code: 24 20 0e 36 e0 45 49 c7 04 1f 00 00 00 00 41 c7 44 1f 08 00 00 00 00 65 48 8b 04 25 28 00 00 00 48 3b 84 24 80 00 00 00 75 28 <48> 8d 65 d8 5b 41 5c 41 5d 41 5e 41 5f 5d c3 e8 47 d9 f9 ff 48 c7
RSP: 0018:ffffc90000007800 EFLAGS: 00000046
RAX: d2c93d29cb1ff400 RBX: dffffc0000000000 RCX: f8f8f8f8f8f8f8f8
RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000008
RBP: ffffc900000078c8 R08: ffffffff8d8b0eef R09: 1ffffffff1b161dd
R10: dffffc0000000000 R11: fffffbfff1b161de R12: 000000007f000000
R13: ffffe8ffffc7c00c R14: ffffe8ffffc7c000 R15: 1ffff92000000f04
FS:  000055555d1a1500(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffe7378cf88 CR3: 0000000058854000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 trace_irq_enable_rcuidle+0x108/0x180 include/trace/events/preemptirq.h:40
 trace_hardirqs_on+0x57/0x80 kernel/trace/trace_preemptirq.c:44
 asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:713
RIP: 0010:rcu_read_unlock_special+0x7f/0x4a0 kernel/rcu/tree_plugin.h:674
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 f2 0f 9d 7e 41 f7 c6 00 00 f0 00 74 40 <48> c7 44 24 20 0e 36 e0 45 4a c7 04 2b 00 00 00 00 42 c7 44 2b 08
RSP: 0018:ffffc900000079c0 EFLAGS: 00000206
RAX: d2c93d29cb1ff400 RBX: 1ffff92000000f3c RCX: d2c93d29cb1ff400
RDX: dffffc0000000000 RSI: ffffffff8a2b2be0 RDI: ffffffff8a7a43c0
RBP: ffffc90000007aa0 R08: ffffffff901ef1df R09: 1ffffffff203de3b
R10: dffffc0000000000 R11: fffffbfff203de3c R12: ffffffff8c323400
R13: dffffc0000000000 R14: 0000000000000246 R15: 0000000000000001
 __rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:422
 rcu_read_unlock include/linux/rcupdate.h:772 [inline]
 hsr_announce+0x29a/0x310 net/hsr/hsr_device.c:410
 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_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1108
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:call_rcu+0x697/0x900 kernel/rcu/tree.c:3092
Code: f7 84 24 a0 00 00 00 00 02 00 00 43 c6 44 25 04 f8 75 4f f7 44 24 58 00 02 00 00 74 01 fb 48 c7 84 24 80 00 00 00 0e 36 e0 45 <4b> c7 44 25 00 00 00 00 00 43 c7 44 25 08 00 00 00 00 65 48 8b 04
RSP: 0018:ffffc9000cfa7d40 EFLAGS: 00000206
RAX: d2c93d29cb1ff400 RBX: ffff88802ce10c80 RCX: d2c93d29cb1ff400
RDX: dffffc0000000000 RSI: ffffffff8a2b2be0 RDI: ffffffff8a7a43c0
RBP: ffffc9000cfa7e78 R08: ffff8880b903b30b R09: 1ffff11017207661
R10: dffffc0000000000 R11: ffffed1017207662 R12: dffffc0000000000
R13: 1ffff920019f4fb8 R14: ffff8880b903b2d0 R15: 000000000000001a
 task_work_run+0x125/0x1a0 kernel/task_work.c:188
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop+0x10f/0x130 kernel/entry/common.c:181
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f5a86a1f159
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:00007ffdb617dea8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007ffdb617df90 RCX: 00007f5a86a1f159
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 0000000000037dd3 R08: 0000000000000001 R09: 0000000000000000
R10: 0000001b30d20000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5a86ca6fac R14: 00007f5a86ca6fa8 R15: 00007f5a86ca6fa0
 </TASK>

Crashes (8):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/31 07:11 linux-5.15.y 28c35638ec51 2f52988a .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in task_work_run
2025/12/12 00:06 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in task_work_run
2025/12/10 23:06 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in task_work_run
2025/10/19 13:41 linux-5.15.y 29e53a5b1c4f 1c8c8cd8 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in task_work_run
2025/09/13 23:37 linux-5.15.y 43bb85222e53 e2beed91 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in task_work_run
2026/03/09 08:11 linux-5.15.y 91d48252ad4b 5cb44a80 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in task_work_run
2026/02/17 05:53 linux-5.15.y e45d5d41c134 e439b951 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in task_work_run
2026/01/07 06:40 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in task_work_run
* Struck through repros no longer work on HEAD.