INFO: rcu detected stall in kthread_worker_fn (2)

Status: upstream: reported syz repro on 2025/03/13 09:29
Subsystems: kernel
[Documentation on labels]
Reported-by: syzbot+2ea3f3959d6a151d0865@syzkaller.appspotmail.com
First crash: 513d, last: 13d
Cause bisection: introduced by (bisect log) :
commit 5a781ccbd19e4664babcbe4b4ead7aa2b9283d22
Author: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Date: Sat Sep 29 00:59:43 2018 +0000

  tc: Add support for configuring the taprio scheduler

Crash: no output from test machine (log)
Repro: syz .config
  
Fix bisection: failed (error log, bisect log)
  
▶ ▼ ✨ AI Jobs (6)
ID Workflow Result Correct Bug Created Started Finished Revision Error
f98b6de0 assessment-security 💥 INFO: rcu detected stall in kthread_worker_fn (2) 2026/07/05 06:16 2026/07/05 06:16 2026/07/05 06:41 93f57954 
failed to run ["make" "KERNELVERSION=syzkaller" "KERNELRELEASE=syzkaller" "LOCALVERSION=-syzkaller" "-j" "32" "ARCH=x86_64" "CC=ccache clang" "LD=ld.lld" "O=/app/workdir/cache/build/32bc55683a962153b5...
truncated to first 200 bytes; open job for full error
1c6d722a assessment-security 💥 INFO: rcu detected stall in kthread_worker_fn (2) 2026/06/18 05:50 2026/06/18 05:50 2026/06/18 06:29 b62b3ded 
failed to run ["make" "KERNELVERSION=syzkaller" "KERNELRELEASE=syzkaller" "LOCALVERSION=-syzkaller" "-j" "32" "ARCH=x86_64" "CC=ccache clang" "LD=ld.lld" "O=/app/workdir/cache/build/32bc55683a962153b5...
truncated to first 200 bytes; open job for full error
7ff4d3bd assessment-security 💥 INFO: rcu detected stall in kthread_worker_fn (2) 2026/06/10 01:43 2026/06/10 01:43 2026/06/10 02:10 c36c07f6 
failed to run ["make" "KERNELVERSION=syzkaller" "KERNELRELEASE=syzkaller" "LOCALVERSION=-syzkaller" "-j" "32" "ARCH=x86_64" "CC=ccache clang" "LD=ld.lld" "O=/app/workdir/cache/build/32bc55683a962153b5...
truncated to first 200 bytes; open job for full error
26dd9823 assessment-security 💥 INFO: rcu detected stall in kthread_worker_fn (2) 2026/06/04 04:15 2026/06/04 04:15 2026/06/04 04:35 62fe1528 
failed to run ["make" "KERNELVERSION=syzkaller" "KERNELRELEASE=syzkaller" "LOCALVERSION=-syzkaller" "-j" "32" "ARCH=x86_64" "CC=ccache clang" "LD=ld.lld" "O=/app/workdir/cache/build/32bc55683a962153b5...
truncated to first 200 bytes; open job for full error
d550d69a assessment-security 💥 INFO: rcu detected stall in kthread_worker_fn (2) 2026/06/01 21:20 2026/06/01 21:20 2026/06/01 21:53 386cc6da 
failed to run ["make" "KERNELVERSION=syzkaller" "KERNELRELEASE=syzkaller" "LOCALVERSION=-syzkaller" "-j" "32" "ARCH=x86_64" "CC=ccache clang" "LD=ld.lld" "O=/app/workdir/cache/build/32bc55683a962153b5...
truncated to first 200 bytes; open job for full error
5af426de assessment-security 💥 INFO: rcu detected stall in kthread_worker_fn (2) 2026/05/18 08:13 2026/05/18 08:13 2026/05/18 08:42 de5aae85 
failed to run ["make" "KERNELVERSION=syzkaller" "KERNELRELEASE=syzkaller" "LOCALVERSION=-syzkaller" "-j" "32" "ARCH=x86_64" "CC=ccache clang" "LD=ld.lld" "O=/app/workdir/cache/build/32bc55683a962153b5...
truncated to first 200 bytes; open job for full error
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [kernel?] INFO: rcu detected stall in kthread_worker_fn (2) 0 (1) 2025/03/13 09:29
▶ ▼ Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in kthread_worker_fn kernel 1 12 618d 841d 0/29 auto-obsoleted due to no activity on 2025/02/16 10:22
▶ ▼ Last patch testing requests (10)
Created Duration User Patch Repo Result
2026/06/23 02:18 58m retest repro upstream log
2026/06/10 05:09 38m retest repro upstream log
2026/06/10 05:08 24m retest repro upstream log
2026/04/13 13:21 17m retest repro upstream report log
2026/02/02 10:44 20m retest repro upstream report log
2025/11/30 03:39 20m retest repro upstream report log
2025/11/18 08:39 1h11m retest repro upstream report log
2025/09/21 02:41 25m retest repro upstream report log
2025/09/09 06:53 21m retest repro upstream report log
2025/06/27 02:35 1h14m retest repro upstream report log
▶ ▼ Fix bisection attempts (4)
Created Duration User Patch Repo Result
2026/02/18 07:55 1m bisect fix upstream error job log
2025/12/15 08:39 2h35m bisect fix upstream OK (0) job log log
2025/07/12 19:27 5h19m bisect fix upstream OK (0) job log log
2025/05/21 17:41 2h51m bisect fix upstream OK (0) job log log

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-...!: (0 ticks this GP) idle=bbfc/1/0x4000000000000000 softirq=14781/14781 fqs=0
rcu: 	(detected by 1, t=10502 jiffies, g=11189, q=106 ncpus=2)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 20 Comm: rcu_exp_gp_kthr Not tainted 6.14.0-rc7-syzkaller-00137-g5fc319360819 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
RIP: 0010:lockdep_recursion_finish kernel/locking/lockdep.c:469 [inline]
RIP: 0010:lock_is_held_type+0xf5/0x190 kernel/locking/lockdep.c:5924
Code: ee e8 cf 5a 25 f9 eb cb 31 db eb 1e 41 83 fe ff 74 13 31 c0 f6 43 22 03 0f 95 c0 31 db 44 39 f0 0f 94 c3 eb 05 bb 01 00 00 00 <48> c7 c7 00 c6 2a 8c e8 7f 1a 00 00 b8 ff ff ff ff 65 0f c1 05 62
RSP: 0018:ffffc90000007c28 EFLAGS: 00000046
RAX: 0000000000000001 RBX: 0000000000000001 RCX: ffff88801d69da00
RDX: ffff88801d69da00 RSI: ffff888027cac300 RDI: ffff88801d69e4f0
RBP: 0000000000000000 R08: ffffffff8a05262b R09: fffff52000000f7c
R10: dffffc0000000000 R11: fffff52000000f7c R12: 0000000000000046
R13: ffff88801d69da00 R14: 00000000ffffffff R15: ffff888027cac300
FS:  0000000000000000(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000600 CR3: 000000002f914000 CR4: 0000000000350ef0
Call Trace:
 <NMI>
 </NMI>
 <IRQ>
 lock_is_held include/linux/lockdep.h:249 [inline]
 advance_sched+0xcd/0xca0 net/sched/sch_taprio.c:925
 __run_hrtimer kernel/time/hrtimer.c:1801 [inline]
 __hrtimer_run_queues+0x59d/0xd30 kernel/time/hrtimer.c:1865
 hrtimer_interrupt+0x403/0xa40 kernel/time/hrtimer.c:1927
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1038 [inline]
 __sysvec_apic_timer_interrupt+0x112/0x420 arch/x86/kernel/apic/apic.c:1055
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1049 [inline]
 sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1049
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xd8/0x140 kernel/locking/spinlock.c:194
Code: 9c 8f 44 24 20 42 80 3c 23 00 74 08 4c 89 f7 e8 4e 59 1d f6 f6 44 24 21 02 75 52 41 f7 c7 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> b3 bc 83 f5 65 8b 05 a4 0f f8 73 85 c0 74 43 48 c7 04 24 0e 36
RSP: 0018:ffffc90000197820 EFLAGS: 00000206
RAX: 85548c2d7975cc00 RBX: 1ffff92000032f08 RCX: ffffffff9a654903
RDX: dffffc0000000000 RSI: ffffffff8c2ab3a0 RDI: 0000000000000001
RBP: ffffc900001978b0 R08: ffffffff903cfb77 R09: 1ffffffff2079f6e
R10: dffffc0000000000 R11: fffffbfff2079f6f R12: dffffc0000000000
R13: 1ffff92000032f04 R14: ffffc90000197840 R15: 0000000000000246
 debug_object_assert_init+0x2dd/0x4b0 lib/debugobjects.c:1009
 debug_timer_assert_init kernel/time/timer.c:845 [inline]
 debug_assert_init kernel/time/timer.c:890 [inline]
 __try_to_del_timer_sync+0x29/0x390 kernel/time/timer.c:1499
 __timer_delete_sync+0x245/0x310 kernel/time/timer.c:1662
 del_timer_sync include/linux/timer.h:185 [inline]
 schedule_timeout+0x162/0x290 kernel/time/sleep_timeout.c:100
 synchronize_rcu_expedited_wait_once kernel/rcu/tree_exp.h:543 [inline]
 synchronize_rcu_expedited_wait kernel/rcu/tree_exp.h:656 [inline]
 rcu_exp_wait_wake kernel/rcu/tree_exp.h:685 [inline]
 rcu_exp_sel_wait_wake+0x779/0x1dc0 kernel/rcu/tree_exp.h:719
 kthread_worker_fn+0x4f9/0xb70 kernel/kthread.c:1010
 kthread+0x7ab/0x920 kernel/kthread.c:464
 ret_from_fork+0x4d/0x80 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
rcu: rcu_preempt kthread timer wakeup didn't happen for 10501 jiffies! g11189 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: 	Possible timer handling issue on cpu=0 timer-softirq=3110
rcu: rcu_preempt kthread starved for 10502 jiffies! g11189 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:26104 pid:18    tgid:18    ppid:2      task_flags:0x208040 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5378 [inline]
 __schedule+0x190e/0x4c90 kernel/sched/core.c:6765
 __schedule_loop kernel/sched/core.c:6842 [inline]
 schedule+0x14b/0x320 kernel/sched/core.c:6857
 schedule_timeout+0x15a/0x290 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x2df/0x1330 kernel/rcu/tree.c:2024
 rcu_gp_kthread+0xa7/0x3b0 kernel/rcu/tree.c:2226
 kthread+0x7ab/0x920 kernel/kthread.c:464
 ret_from_fork+0x4d/0x80 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>

Crashes (20):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/03/21 06:14 upstream 5fc319360819 62330552 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in kthread_worker_fn
2025/03/09 09:16 upstream b7c90e3e717a 163f510d .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root INFO: rcu detected stall in kthread_worker_fn
2026/07/15 19:56 upstream 58717b2a1365 209f0369 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in kthread_worker_fn
2026/07/13 14:15 upstream a13c140cc289 a870962e .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in kthread_worker_fn
2026/05/17 05:57 upstream 6916d5703ddf de5aae85 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in kthread_worker_fn
2026/05/07 08:11 upstream 5862221fdded f250db59 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in kthread_worker_fn
2026/04/23 08:45 upstream 2a4c0c11c019 b10da5ec .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in kthread_worker_fn
2026/04/22 20:15 upstream 6596a02b2078 4595e353 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in kthread_worker_fn
2025/12/28 17:14 upstream d26143bb38e2 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in kthread_worker_fn
2025/10/27 20:12 upstream fd57572253bc fd2207e7 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in kthread_worker_fn
2025/08/26 06:16 upstream fab1beda7597 bf27483f .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in kthread_worker_fn
2025/06/12 11:09 upstream 2c4a1f3fe03e 98683f8f .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in kthread_worker_fn
2025/04/16 10:27 upstream 1a1d569a75f3 23b969b7 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in kthread_worker_fn
2025/03/11 01:25 upstream 4d872d51bc9d 16256247 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in kthread_worker_fn
2025/03/02 18:55 upstream 1973160c90d7 c3901742 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root INFO: rcu detected stall in kthread_worker_fn
2026/05/26 13:11 net-next 3baa7ba4ab98 a3e47276 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce INFO: rcu detected stall in kthread_worker_fn
2026/01/19 06:53 net-next b4e486e2c46f d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce INFO: rcu detected stall in kthread_worker_fn
2026/01/12 12:44 net-next 60d8484c4cec d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce INFO: rcu detected stall in kthread_worker_fn
2026/01/11 15:12 net-next 60d8484c4cec d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce INFO: rcu detected stall in kthread_worker_fn
2025/10/13 20:15 linux-next 52ba76324a9d b6605ba8 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root INFO: rcu detected stall in kthread_worker_fn
* Struck through repros no longer work on HEAD.