syzbot


INFO: rcu detected stall in sys_getpid (3)

Status: upstream: reported on 2026/05/20 20:58
Reported-by: syzbot+51bc0c08938dfe165e48@syzkaller.appspotmail.com
First crash: 1d03h, last: 4h20m
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 152d 301d 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 C inconclusive 6 8d17h 257d 0/2 upstream: reported C repro on 2025/09/06 16:11
linux-5.15 INFO: rcu detected stall in sys_getpid 1 1 694d 694d 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 391d 391d 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 109d 170d 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 C error 21 79d 537d 0/3 upstream: reported C repro on 2024/11/30 21:19

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
	(detected by 1, t=10502 jiffies, g=102717, q=35 ncpus=2)
rcu: All QSes seen, last rcu_preempt kthread activity 10480 (4295094584-4295084104), jiffies_till_next_fqs=1, root ->qsmask 0x0
rcu: rcu_preempt kthread starved for 10480 jiffies! g102717 f0x2 RCU_GP_CLEANUP(7) ->state=0x0 ->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:R  running task     stack:28016 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_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_irq include/linux/spinlock_api_smp.h:160 [inline]
 _raw_spin_unlock_irq+0x3c/0x40 kernel/locking/spinlock.c:202
 rcu_gp_cleanup+0x4e4/0xc90 kernel/rcu/tree.c:1821
 rcu_gp_kthread+0xa7/0x3b0 kernel/rcu/tree.c:1909
 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 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 17544 Comm: syz.0.3283 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:timerqueue_getnext include/linux/timerqueue.h:36 [inline]
RIP: 0010:__hrtimer_next_event_base+0xa7/0x2d0 kernel/time/hrtimer.c:542
Code: 09 00 00 00 44 89 fe e8 97 24 10 00 41 83 ff 09 0f 83 00 02 00 00 e8 28 21 10 00 48 c1 e5 07 48 03 6c 24 18 0f 84 fa 01 00 00 <4c> 8d 7d 58 4c 89 f8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df 80
RSP: 0018:ffffc90000007e38 EFLAGS: 00000082
RAX: ffffffff81726588 RBX: 0000000000000000 RCX: ffff8880769a8000
RDX: 0000000000010000 RSI: 0000000000000000 RDI: 0000000000000009
RBP: ffff8880b8e2a640 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff52000000f84 R12: 7fffffffffffffff
R13: 7fffffffffffffff R14: 0000000000000000 R15: 0000000000000000
FS:  00007f00ca26f6c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000058 CR3: 000000006761f000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 __hrtimer_get_next_event kernel/time/hrtimer.c:615 [inline]
 hrtimer_update_next_event kernel/time/hrtimer.c:640 [inline]
 hrtimer_interrupt+0x4e6/0x9c0 kernel/time/hrtimer.c:1876
 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:lock_acquire+0x225/0x4a0 kernel/locking/lockdep.c:5666
Code: f7 84 24 80 00 00 00 00 02 00 00 43 c6 44 3d 04 f8 0f 85 f0 00 00 00 41 f7 c6 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 44 3d 00 00 00 00 00 43 c7 44 3d 08 00 00 00 00 65 48 8b 04
RSP: 0018:ffffc90003ec7da0 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: 77aa5a8c34000a00
RDX: 0000000000000000 RSI: ffffffff8a8c2b20 RDI: ffffffff8adf1ba0
RBP: ffffc90003ec7ec0 R08: dffffc0000000000 R09: 1ffffffff215f448
R10: dffffc0000000000 R11: fffffbfff215f449 R12: 0000000000000000
R13: 1ffff920007d8fc0 R14: 0000000000000246 R15: dffffc0000000000
 rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
 rcu_read_lock include/linux/rcupdate.h:791 [inline]
 __task_pid_nr_ns+0x44/0x460 kernel/pid.c:497
 task_tgid_vnr include/linux/sched.h:1631 [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: 0033:0x7f00c9396bd7
Code: 8d 3d 3e 8a 0b 00 e8 58 1d fa ff e8 a3 87 00 00 0f 1f 00 b8 68 00 00 00 0f 05 c3 0f 1f 84 00 00 00 00 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 0f 1f 84 00 00
RSP: 002b:00007f00ca26eb08 EFLAGS: 00000202 ORIG_RAX: 0000000000000027
RAX: ffffffffffffffda RBX: 00007f00ca26ec70 RCX: 00007f00c9396bd7
RDX: 00007f00ca26eb40 RSI: 00007f00ca26ec70 RDI: 0000000000000021
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000
R13: 00007f00c9616038 R14: 00007ffd515c73d0 R15: 00007ffd515c74b8
 </TASK>

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
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.