INFO: rcu detected stall in sys_getpid (3)

Status: upstream: reported C repro on 2026/05/20 20:58
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+51bc0c08938dfe165e48@syzkaller.appspotmail.com
First crash: 176d, last: 50d
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2026/10/19 linux-6.1.y (ToT) 79807e970724 C [report] INFO: rcu detected stall in corrupted
2026/09/29 upstream (ToT) a243ede71846 C Didn't crash
▶ ▼ Similar bugs (6)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in sys_getpid kernel 1 5 327d 477d 0/29 auto-obsoleted due to no activity on 2026/03/20 23:07
linux-6.6 INFO: rcu detected stall in sys_getpid origin:lts-only 1 syz, C inconclusive 11 102d 432d 0/2 upstream: reported C repro on 2025/09/06 16:11
linux-5.15 INFO: rcu detected stall in sys_getpid 1 1 869d 869d 0/3 auto-obsoleted due to no activity on 2024/10/04 19:18
linux-6.1 INFO: rcu detected stall in sys_getpid 1 1 567d 567d 0/3 auto-obsoleted due to no activity on 2025/08/03 12:49
linux-6.1 INFO: rcu detected stall in sys_getpid (2) 1 2 285d 345d 0/3 auto-obsoleted due to no activity on 2026/05/12 11:26
linux-5.15 INFO: rcu detected stall in sys_getpid (2) origin:lts-only 1 syz, C error 27 23d 712d 0/3 upstream: reported C repro on 2024/11/30 21:19
▶ ▼ Fix bisection attempts (1)
Created Duration User Patch Repo Result
2026/09/22 09:49 3h35m bisect fix linux-6.1.y OK (0) job log log

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P4299/1:b..l
	(detected by 0, t=10503 jiffies, g=8301, q=150 ncpus=2)
task:syz-executor136 state:R  running task     stack:26288 pid:4299  ppid:4297   flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5245 [inline]
 __schedule+0x107f/0x4030 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:__preempt_count_add kernel/rcu/tree.c:717 [inline]
RIP: 0010:rcu_is_watching+0x4/0xa0 kernel/rcu/tree.c:720
Code: 92 27 c4 08 48 c7 c7 60 46 b3 8c 4c 89 f6 e8 b3 e3 d0 02 e9 44 ff ff ff 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 41 57 41 56 <53> 65 ff 05 8c 4c 96 7e e8 0f 3c c4 08 89 c3 83 f8 08 73 60 49 bf
RSP: 0018:ffffc90003f27ec0 EFLAGS: 00000202
RAX: ffffffff8155f89a RBX: ffff88807e40a640 RCX: 0000000000000000
RDX: ffff8880206d8000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: 00000000000010cb R08: dffffc0000000000 R09: 1ffffffff2162048
R10: dffffc0000000000 R11: fffffbfff2162049 R12: ffff88807e40a718
R13: dffffc0000000000 R14: 0000000000000001 R15: 0000000000000000
 rcu_read_unlock include/linux/rcupdate.h:820 [inline]
 __task_pid_nr_ns+0x314/0x460 kernel/pid.c:501
 task_tgid_vnr include/linux/sched.h:1635 [inline]
 __ia32_sys_getpid+0x19/0x20 kernel/sys.c:953
 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: 0033:0x7ff077a65077
RSP: 002b:00007ffec716b908 EFLAGS: 00000202 ORIG_RAX: 0000000000000027
RAX: ffffffffffffffda RBX: 00007ffec716ba70 RCX: 00007ff077a65077
RDX: 00007ffec716b940 RSI: 00007ffec716ba70 RDI: 0000000000000021
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 001e1693921c4480 R11: 0000000000000202 R12: 0000000000000005
R13: 00007ff077b15b20 R14: 00007ff077b15b2c R15: 00000000000003e8
 </TASK>
rcu: rcu_preempt kthread starved for 10531 jiffies! g8301 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->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:I stack:27840 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
 preempt_schedule_common+0x82/0xd0 kernel/sched/core.c:6731
 preempt_schedule+0xbc/0xd0 kernel/sched/core.c:6755
 preempt_schedule_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:34
 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
 _raw_spin_unlock_irqrestore+0x10d/0x120 kernel/locking/spinlock.c:194
 init_timer_on_stack_key kernel/time/timer.c:805 [inline]
 schedule_timeout+0x12d/0x2d0 kernel/time/timer.c:2166
 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: 52 Comm: kworker/1:1H Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Workqueue: kblockd blk_mq_timeout_work
RIP: 0010:bytes_is_nonzero mm/kasan/generic.c:85 [inline]
RIP: 0010:memory_is_nonzero mm/kasan/generic.c:102 [inline]
RIP: 0010:memory_is_poisoned_n mm/kasan/generic.c:128 [inline]
RIP: 0010:memory_is_poisoned mm/kasan/generic.c:159 [inline]
RIP: 0010:check_region_inline mm/kasan/generic.c:180 [inline]
RIP: 0010:kasan_check_range+0x80/0x290 mm/kasan/generic.c:189
Code: ff 4d 89 c1 49 c1 e9 03 4b 8d 1c 21 49 89 df 4d 29 df 49 83 ff 10 7f 29 4d 85 ff 0f 84 38 01 00 00 4c 89 cb 48 f7 d3 4c 01 f3 <41> 80 3b 00 0f 85 86 01 00 00 49 ff c3 48 ff c3 75 ee e9 18 01 00
RSP: 0018:ffffc900001e0b78 EFLAGS: 00000086
RAX: 1ffffffff18cbf01 RBX: ffffffffffffffff RCX: ffffffff81594e5a
RDX: 0000000000000001 RSI: 0000000000000010 RDI: ffffc900001e0be8
RBP: 0000000000000000 R08: ffffc900001e0bf7 R09: 1ffff9200003c17e
R10: dffffc0000000000 R11: fffff5200003c17e R12: dffffc0000000001
R13: ffff8880206c0014 R14: 1ffff9200003c17d R15: 0000000000000002
FS:  0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000058 CR3: 0000000077ab6000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 memset+0x1e/0x40 mm/kasan/shadow.c:44
 ttwu_queue kernel/sched/core.c:3898 [inline]
 try_to_wake_up+0x4ba/0x10b0 kernel/sched/core.c:4228
 signal_wake_up_state kernel/signal.c:781 [inline]
 signal_wake_up include/linux/sched/signal.h:457 [inline]
 complete_signal+0x806/0xc50 kernel/signal.c:1075
 send_sigqueue+0x380/0x5e0 kernel/signal.c:2005
 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:finish_task_switch+0x267/0x8e0 kernel/sched/core.c:5124
Code: d6 08 85 c0 0f 84 38 01 00 00 48 85 db 0f 85 57 01 00 00 0f 1f 44 00 00 4c 89 e7 e8 d3 e3 e0 08 e8 8e 04 2f 00 fb 4c 8b 65 b8 <49> 8d bc 24 f8 15 00 00 48 89 f8 48 c1 e8 03 42 0f b6 04 30 84 c0
RSP: 0018:ffffc90000bd75c0 EFLAGS: 00000282
RAX: f03a91c3b1cb8000 RBX: 0000000000000000 RCX: f03a91c3b1cb8000
RDX: dffffc0000000000 RSI: ffffffff8a8c17a0 RDI: ffffffff8adf42e0
RBP: ffffc90000bd7610 R08: ffffffff90b102a7 R09: 1ffffffff2162054
R10: dffffc0000000000 R11: fffffbfff2162055 R12: ffff8880192cbc00
R13: 1ffff110171e76fa R14: dffffc0000000000 R15: ffff8880b8f3b7d0
 context_switch kernel/sched/core.c:5248 [inline]
 __schedule+0x1087/0x4030 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:blk_mq_queue_tag_busy_iter+0x2db/0x7e0 block/blk-mq-tag.c:522
Code: a0 01 00 00 00 00 00 00 48 8b 44 24 18 48 8d 78 48 48 89 7c 24 20 48 c7 c2 ff ff ff ff b9 08 00 00 00 e8 a8 7a 26 06 48 85 c0 <0f> 84 ff 02 00 00 49 89 c6 48 8d 84 24 b0 00 00 00 48 83 c0 21 48
RSP: 0018:ffffc90000bd7920 EFLAGS: 00000286
RAX: ffff8880258bc800 RBX: 0000000000000000 RCX: ffff8880192cbc00
RDX: 0000000000000000 RSI: ffffffff8a8c2920 RDI: ffffffff8adf42e0
RBP: ffffc90000bd7b30 R08: ffffffff8e2121af R09: 1ffffffff1c42435
R10: dffffc0000000000 R11: fffffbfff1c42436 R12: dffffc0000000000
R13: 1ffff9200017af2c R14: ffff888019f241f8 R15: ffff888019f24250
 blk_mq_timeout_work+0x103/0x380 block/blk-mq.c:1665
 process_one_work+0x8ab/0x1160 kernel/workqueue.c:2292
 worker_thread+0xaf5/0x12a0 kernel/workqueue.c:2439
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>
INFO: NMI handler (nmi_cpu_backtrace_handler) took too long to run: 1.411 msecs

Crashes (7):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/18 22:03 linux-6.1.y 090666d3cc90 72524a66 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_getpid
2026/08/18 17:03 linux-6.1.y e4f7d8be268e 1e72964b .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_getpid
2026/09/24 06:14 linux-6.1.y 1a8763b93150 0281b448 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_getpid
2026/07/24 07:00 linux-6.1.y 090666d3cc90 544adce9 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_getpid
2026/06/16 02:08 linux-6.1.y 228da13e907e 50bb0618 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_getpid
2026/05/21 20:04 linux-6.1.y c27210688955 e195359d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_getpid
2026/05/20 20:58 linux-6.1.y c27210688955 62fb93a2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_getpid
* Struck through repros no longer work on HEAD.