INFO: rcu detected stall in syscall_enter_from_user_mode (3)

Status: upstream: reported C repro on 2025/02/27 13:22
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+d27661ce10e475e27efe@syzkaller.appspotmail.com
First crash: 557d, last: 5d11h
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

  
Fix bisection: the issue occurs on the latest tested release (bisect log)
Crash: no output from test machine (log)
Repro: syz .config
  
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2025/08/27 linux-6.1.y (ToT) 0bc96de781b4 C [report] INFO: rcu detected stall in perf_event_open
2025/08/27 upstream (ToT) 39f90c196721 C Didn't crash
▶ ▼ Similar bugs (9)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.6 INFO: rcu detected stall in syscall_enter_from_user_mode (2) origin:lts-only 1 syz, C 2 9d23h 71d 0/2 upstream: reported C repro on 2026/06/28 07:45
linux-6.1 INFO: rcu detected stall in syscall_enter_from_user_mode (2) 1 1 763d 763d 0/3 auto-obsoleted due to no activity on 2024/11/13 07:03
linux-6.1 INFO: rcu detected stall in syscall_enter_from_user_mode 1 1 1160d 1160d 0/3 auto-obsoleted due to no activity on 2023/10/13 06:46
upstream INFO: rcu detected stall in syscall_enter_from_user_mode (2) kernel 1 11 1336d 1625d 0/29 auto-obsoleted due to no activity on 2023/04/22 11:15
upstream INFO: rcu detected stall in syscall_enter_from_user_mode (3) kernel 1 5 1000d 1165d 0/29 auto-obsoleted due to no activity on 2024/03/11 14:48
linux-5.15 INFO: rcu detected stall in syscall_enter_from_user_mode missing-backport origin:upstream 1 syz, C done 181 7d18h 999d 0/3 upstream: reported C repro on 2023/12/13 03:22
linux-6.6 INFO: rcu detected stall in syscall_enter_from_user_mode 1 1 300d 300d 0/2 auto-obsoleted due to no activity on 2026/02/19 17:17
upstream INFO: rcu detected stall in syscall_enter_from_user_mode kernel 1 2 1682d 1696d 0/29 closed as invalid on 2022/02/08 10:10
android-5-15 BUG: soft lockup in syscall_enter_from_user_mode 1 1 844d 844d 0/2 auto-obsoleted due to no activity on 2024/08/14 14:14
▶ ▼ Fix bisection attempts (4)
Created Duration User Patch Repo Result
2025/11/13 01:20 11h02m fix candidate upstream OK (1) job log
2025/06/27 04:15 2h09m fix candidate upstream OK (0) job log
2025/06/06 18:47 2h16m bisect fix linux-6.1.y OK (0) job log log
2025/04/07 14:34 2h31m 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 0, t=10502 jiffies, g=8365, q=216 ncpus=2)
rcu: All QSes seen, last rcu_preempt kthread activity 10503 (4294979351-4294968848), jiffies_till_next_fqs=1, root ->qsmask 0x0
rcu: rcu_preempt kthread starved for 10504 jiffies! g8365 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:27888 pid:16    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5245 [inline]
 __schedule+0x107f/0x4030 kernel/sched/core.c:6562
 schedule+0xb9/0x180 kernel/sched/core.c:6638
 schedule_timeout+0x184/0x2d0 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x303/0x1350 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:
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 4355 Comm: syz-executor408 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:__kasan_check_read+0x0/0x10 mm/kasan/shadow.c:31
Code: 41 5c 41 5d 41 5e 41 5f 5d c3 48 c7 c7 ea ce 60 8c eb 0a 48 c7 c7 01 76 45 8c 48 89 de e8 98 5b 4c 08 31 ed eb d7 00 00 cc cc <89> f6 48 8b 0c 24 31 d2 e9 c3 ec ff ff 0f 1f 00 89 f6 48 8b 0c 24
RSP: 0018:ffffc900001e0838 EFLAGS: 00000002
RAX: 00000000000000e0 RBX: 0000000000000000 RCX: ffff888023c5bc00
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff90af2320
RBP: ffffc900001e0a70 R08: dffffc0000000000 R09: 1ffffffff215e44a
R10: dffffc0000000000 R11: fffffbfff215e44b R12: ffff888023c5c700
R13: ffff888023c5bc02 R14: 000000000000070b R15: ffff888023c5c700
FS:  00005555908b6480(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fce6f5abed0 CR3: 00000000285cd000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 instrument_atomic_read include/linux/instrumented.h:72 [inline]
 _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
 hlock_class kernel/locking/lockdep.c:228 [inline]
 check_wait_context kernel/locking/lockdep.c:4748 [inline]
 __lock_acquire+0x929/0x7bd0 kernel/locking/lockdep.c:4999
 lock_acquire+0x1bb/0x4a0 kernel/locking/lockdep.c:5662
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
 _raw_spin_lock_irqsave+0xb0/0x100 kernel/locking/spinlock.c:162
 __lock_task_sighand+0x146/0x2d0 kernel/signal.c:1412
 lock_task_sighand include/linux/sched/signal.h:745 [inline]
 send_sigqueue+0x162/0x5e0 kernel/signal.c:1980
 posix_timer_event kernel/time/posix-timers.c:360 [inline]
 posix_timer_fn+0x149/0x350 kernel/time/posix-timers.c:386
 __run_hrtimer kernel/time/hrtimer.c:1751 [inline]
 __hrtimer_run_queues+0x522/0xc90 kernel/time/hrtimer.c:1815
 hrtimer_interrupt+0x399/0x980 kernel/time/hrtimer.c:1877
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1107 [inline]
 __sysvec_apic_timer_interrupt+0x153/0x5a0 arch/x86/kernel/apic/apic.c:1124
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
 sysvec_apic_timer_interrupt+0x9b/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:__syscall_enter_from_user_work kernel/entry/common.c:97 [inline]
RIP: 0010:syscall_enter_from_user_mode+0x2a/0x80 kernel/entry/common.c:118
Code: 41 56 53 48 89 f3 49 89 fe 48 8b 7c 24 10 e8 ed fa ff ff 66 90 66 90 e8 a4 a8 5d f7 e8 1f a7 5d f7 fb 65 48 8b 05 86 8e d7 75 <48> 8b 70 08 40 f6 c6 3f 74 0b 4c 89 f7 5b 41 5e e9 a1 08 44 f7 48
RSP: 0018:ffffc90004557f08 EFLAGS: 00000286
RAX: ffff888023c5bc00 RBX: 0000000000000027 RCX: e970e9f181ab2800
RDX: dffffc0000000000 RSI: ffffffff8a8c17a0 RDI: ffffffff8adee1a0
RBP: ffffc90004557f48 R08: ffffffff8e200f6f R09: 1ffffffff1c401ed
R10: dffffc0000000000 R11: fffffbfff1c401ee R12: 0000000000000000
R13: 0000000000000000 R14: ffffc90004557f58 R15: 0000000000000000
 do_syscall_64+0x24/0xa0 arch/x86/entry/common.c:72
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fce6f503b57
Code: 1a 07 00 ba 55 00 00 00 48 8d 35 cc df 06 00 48 8d 3d dc df 06 00 e8 88 e7 fd ff e8 d3 24 00 00 0f 1f 00 b8 27 00 00 00 0f 05 <c3> 0f 1f 84 00 00 00 00 00 b8 6e 00 00 00 0f 05 c3 66 2e 0f 1f 84
RSP: 002b:00007ffe0bc7d448 EFLAGS: 00000206 ORIG_RAX: 0000000000000027
RAX: ffffffffffffffda RBX: 00007ffe0bc7d5b0 RCX: 00007fce6f503b57
RDX: 00007ffe0bc7d480 RSI: 00007ffe0bc7d5b0 RDI: 0000000000000021
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 00007fce6f5abed0 R14: 00007fce6f5af248 R15: 00007fce6f5af260
 </TASK>

Crashes (21):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/06/22 13:02 linux-6.1.y fdb6fcb41cc7 43bfcdb0 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in syscall_enter_from_user_mode
2026/04/01 17:03 linux-6.1.y 1989cd3d56e2 9a1f7828 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in syscall_enter_from_user_mode
2026/03/21 21:33 linux-6.1.y f2ddafa93a25 5b92003d .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in syscall_enter_from_user_mode
2025/11/29 05:36 linux-6.1.y f6e38ae624cf d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in syscall_enter_from_user_mode
2025/08/20 21:50 linux-6.1.y 0bc96de781b4 0b9605c8 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in syscall_enter_from_user_mode
2026/06/17 13:39 linux-6.1.y 228da13e907e 62cc6db3 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in syscall_enter_from_user_mode
2026/01/18 00:54 linux-6.1.y cd9b81672742 20d37d28 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in syscall_enter_from_user_mode
2025/10/16 18:59 linux-6.1.y c2fda4b3f577 19568248 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in syscall_enter_from_user_mode
2025/02/27 13:21 linux-6.1.y 3a8358583626 6a8fcbc4 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in syscall_enter_from_user_mode
2026/09/02 08:36 linux-6.1.y d64a499eea6b 587f6b29 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in syscall_enter_from_user_mode
2026/08/25 20:27 linux-6.1.y 05208478041c a9a1fc32 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in syscall_enter_from_user_mode
2026/08/20 14:57 linux-6.1.y 7e6e67054721 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in syscall_enter_from_user_mode
2026/08/12 03:02 linux-6.1.y e4f7d8be268e f8d35649 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in syscall_enter_from_user_mode
2026/08/10 09:12 linux-6.1.y e4f7d8be268e 5d63f80b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in syscall_enter_from_user_mode
2026/06/14 14:22 linux-6.1.y 228da13e907e 1d2f3589 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in syscall_enter_from_user_mode
2026/02/19 02:49 linux-6.1.y 8ce36b2849ef 77d4d919 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in syscall_enter_from_user_mode
2026/01/30 06:19 linux-6.1.y cd9b81672742 bfa73b7b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in syscall_enter_from_user_mode
2025/11/15 11:47 linux-6.1.y f6e38ae624cf f7988ea4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: rcu detected stall in syscall_enter_from_user_mode
2025/11/11 14:28 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 syscall_enter_from_user_mode
2025/09/21 21:32 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 syscall_enter_from_user_mode
2025/08/15 07:02 linux-6.1.y 3594f306da12 1804e95e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in syscall_enter_from_user_mode
* Struck through repros no longer work on HEAD.