syzbot


INFO: rcu detected stall in schedule_timeout (2)

Status: upstream: reported C repro on 2025/09/02 23:57
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+7dca4d8f5e1c02ee5ebf@syzkaller.appspotmail.com
First crash: 268d, last: 11d
Fix bisection: the issue occurs on the latest tested release (bisect log)
Crash: INFO: rcu detected stall in corrupted (log)
Repro: C syz .config
  
Bug presence (2)
Date Name Commit Repro Result
2025/09/20 linux-6.1.y (ToT) 363a599da6d9 C [report] INFO: rcu detected stall in corrupted
2025/09/20 upstream (ToT) cd89d487374c C Didn't crash
Similar bugs (10)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in schedule_timeout (3) cgroups mm 1 11 2333d 2333d 0/29 closed as invalid on 2020/01/09 08:13
upstream INFO: rcu detected stall in schedule_timeout (7) kernel 1 C error error 43 1d15h 566d 0/29 upstream: reported C repro on 2024/11/09 08:24
upstream INFO: rcu detected stall in schedule_timeout (2) kernel 1 2 2333d 2333d 0/29 closed as invalid on 2020/01/08 05:23
upstream INFO: rcu detected stall in schedule_timeout (4) kernel 1 1 1038d 1038d 0/29 closed as invalid on 2023/09/01 06:44
linux-6.1 INFO: rcu detected stall in schedule_timeout 1 28 706d 771d 0/3 auto-obsoleted due to no activity on 2024/08/31 04:44
upstream INFO: rcu detected stall in schedule_timeout (5) kernel 1 2 944d 979d 0/29 auto-obsoleted due to no activity on 2024/01/26 16:31
upstream INFO: rcu detected stall in schedule_timeout cgroups mm 1 69 2368d 2369d 0/29 closed as invalid on 2019/12/04 14:14
upstream INFO: rcu detected stall in schedule_timeout (6) usb 1 C done 40 585d 742d 28/29 fixed on 2024/10/22 11:57
linux-5.15 INFO: rcu detected stall in schedule_timeout origin:upstream 1 C inconclusive 13 31d 737d 0/3 upstream: reported C repro on 2024/05/22 14:45
linux-6.6 INFO: rcu detected stall in schedule_timeout origin:upstream 1 C error 5 133d 205d 0/2 upstream: reported C repro on 2025/11/04 19:17
Fix bisection attempts (4)
Created Duration User Patch Repo Result
2026/01/16 11:59 2h19m fix candidate upstream OK (0) job log
2025/12/26 20:01 3h08m bisect fix linux-6.1.y OK (0) job log log
2025/11/23 07:04 2h42m bisect fix linux-6.1.y OK (0) job log log
2025/10/23 23:10 2h10m bisect fix linux-6.1.y OK (0) job log log

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
	(detected by 1, t=10502 jiffies, g=9613, q=289 ncpus=2)
rcu: All QSes seen, last rcu_preempt kthread activity 10500 (4294958713-4294948213), jiffies_till_next_fqs=1, root ->qsmask 0x0
rcu: rcu_preempt kthread starved for 10500 jiffies! g9613 f0x2 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:27760 pid:16    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5245 [inline]
 __schedule+0x11d1/0x40e0 kernel/sched/core.c:6562
 preempt_schedule_irq+0xbb/0x160 kernel/sched/core.c:6874
 irqentry_exit+0x63/0x70 kernel/entry/common.c:439
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:__timer_delete_sync+0x1a8/0x2e0 kernel/time/timer.c:1564
Code: 00 4d 85 f6 75 16 e8 77 9a 10 00 eb 15 e8 70 9a 10 00 e8 8b 09 bc 08 4d 85 f6 74 ea e8 61 9a 10 00 fb 65 44 8b 35 f0 82 90 7e <44> 89 f6 81 e6 00 00 0f 00 31 ff e8 a8 9d 10 00 41 81 e6 00 00 0f
RSP: 0018:ffffc90000157ae0 EFLAGS: 00000293
RAX: ffffffff8171ec4f RBX: ffffc90000157be0 RCX: ffff88813fef5940
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90000157bb0 R08: ffffffff8e1ffbef R09: 1ffffffff1c3ff7d
R10: dffffc0000000000 R11: fffffbfff1c3ff7e R12: ffffffff8171ebba
R13: 1ffff9200002af60 R14: 0000000080000000 R15: 0000000000000000
 timer_delete_sync kernel/time/timer.c:1629 [inline]
 del_timer_sync include/linux/timer.h:200 [inline]
 schedule_timeout+0x18e/0x2d0 kernel/time/timer.c:2169
 rcu_gp_fqs_loop+0x303/0x1340 kernel/rcu/tree.c:1706
 rcu_gp_kthread+0x99/0x3b0 kernel/rcu/tree.c:1905
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 1 PID: 4497 Comm: syz.0.37 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:__raw_spin_unlock_irq include/linux/spinlock_api_smp.h:160 [inline]
RIP: 0010:_raw_spin_unlock_irq+0x25/0x40 kernel/locking/spinlock.c:202
Code: 00 00 00 66 90 53 48 89 fb 48 83 c7 18 48 8b 74 24 08 e8 5e c1 2c f7 48 89 df e8 a6 89 2d f7 e8 81 e0 50 f7 fb bf 01 00 00 00 <e8> f6 ed 20 f7 65 8b 05 f7 5f ca 75 85 c0 74 02 5b c3 e8 44 74 c8
RSP: 0000:ffffc90003567bd8 EFLAGS: 00000286
RAX: 5733535010718900 RBX: ffff88802e9b65c0 RCX: 5733535010718900
RDX: dffffc0000000000 RSI: ffffffff8a8c19a0 RDI: 0000000000000001
RBP: ffff88802e9b6a58 R08: ffff88802e9b65c3 R09: 1ffff11005d36cb8
R10: dffffc0000000000 R11: ffffed1005d36cb9 R12: 1ffff11005d36d4b
R13: 0000000000000021 R14: dffffc0000000000 R15: 0000000000000000
FS:  00007f6ef471f6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000058 CR3: 00000000792f0000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 spin_unlock_irq include/linux/spinlock.h:401 [inline]
 get_signal+0x1163/0x1350 kernel/signal.c:2874
 arch_do_signal_or_restart+0xc4/0x1350 arch/x86/kernel/signal.c:871
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 irqentry_exit_to_user_mode+0x5/0x30 kernel/entry/common.c:316
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0033:0x7f6ef379ce57
Code: 83 c8 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
RSP: 002b:00007f6ef471f0e8 EFLAGS: 00000246
RAX: 00000000000000ca RBX: 00007f6ef3a15fa8 RCX: 00007f6ef379ce59
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f6ef3a15fa8
RBP: 00007f6ef3a15fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6ef3a16038 R14: 00007ffd9a90fb20 R15: 00007ffd9a90fc08
 </TASK>

Crashes (6):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/05/17 21:37 linux-6.1.y c27210688955 de5aae85 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in schedule_timeout
2026/04/12 11:50 linux-6.1.y 8e8fc038cad5 38c8e246 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in schedule_timeout
2025/09/16 19:25 linux-6.1.y 3db754f56897 e2beed91 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in schedule_timeout
2026/04/06 07:50 linux-6.1.y 1989cd3d56e2 4440e7c2 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in schedule_timeout
2026/04/06 05:43 linux-6.1.y 1989cd3d56e2 4440e7c2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in schedule_timeout
2025/09/02 23:56 linux-6.1.y f89b6e15694c 96a211bc .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in schedule_timeout
* Struck through repros no longer work on HEAD.