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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: 29d, last: 3d16h
▶ ▼ 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 180d 330d 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 9 2d06h 286d 0/2 upstream: reported C repro on 2025/09/06 16:11
linux-5.15 INFO: rcu detected stall in sys_getpid 1 1 722d 722d 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 420d 420d 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 138d 198d 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 23 4d11h 565d 0/3 upstream: reported C repro on 2024/11/30 21:19

Sample crash report:
rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	0-...!: (10500 ticks this GP) idle=350c/0/0x1 softirq=24596/24596 fqs=0
	(t=10500 jiffies g=27661 q=193 ncpus=2)
rcu: rcu_preempt kthread timer wakeup didn't happen for 10499 jiffies! g27661 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: 	Possible timer handling issue on cpu=0 timer-softirq=22813
rcu: rcu_preempt kthread starved for 10500 jiffies! g27661 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:26864 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
 schedule+0xb9/0x180 kernel/sched/core.c:6638
 schedule_timeout+0x184/0x2d0 kernel/time/timer.c:2168
 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: 0 PID: 0 Comm: swapper/0 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:default_idle+0xb/0x10 arch/x86/kernel/process.c:742
Code: 48 89 df e8 37 34 9a f7 e9 44 ff ff ff e8 cd 06 f6 ff 00 00 cc cc 00 00 cc cc 00 00 cc cc 00 66 90 0f 00 2d a7 5a 4d 00 fb f4 <c3> 0f 1f 40 00 41 57 41 56 53 49 be 00 00 00 00 00 fc ff df 65 48
RSP: 0018:ffffffff8c807d88 EFLAGS: 000002c6
RAX: 4dae34477ee2e100 RBX: ffffffff8a395407 RCX: 4dae34477ee2e100
RDX: 0000000000000001 RSI: ffffffff8a8c1aa0 RDI: ffffffff8adf2060
RBP: ffffffff8c807ec0 R08: ffff8880b8e3580b R09: 1ffff110171c6b01
R10: dffffc0000000000 R11: ffffed10171c6b02 R12: 0000000000000000
R13: dffffc0000000000 R14: ffffffff8c8bc740 R15: 1ffffffff1900fbc
FS:  0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f896d9456b8 CR3: 000000007e581000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 default_idle_call+0x84/0xc0 kernel/sched/idle.c:109
 cpuidle_idle_call kernel/sched/idle.c:199 [inline]
 do_idle+0x250/0x680 kernel/sched/idle.c:323
 cpu_startup_entry+0x3f/0x60 kernel/sched/idle.c:422
 rest_init+0x2dc/0x300 init/main.c:745
 arch_call_rest_init+0xa/0xa init/main.c:904
 start_kernel+0x493/0x53c init/main.c:1151
 secondary_startup_64_no_verify+0xcf/0xdb
 </TASK>
CPU: 0 PID: 0 Comm: swapper/0 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:default_idle+0xb/0x10 arch/x86/kernel/process.c:742
Code: 48 89 df e8 37 34 9a f7 e9 44 ff ff ff e8 cd 06 f6 ff 00 00 cc cc 00 00 cc cc 00 00 cc cc 00 66 90 0f 00 2d a7 5a 4d 00 fb f4 <c3> 0f 1f 40 00 41 57 41 56 53 49 be 00 00 00 00 00 fc ff df 65 48
RSP: 0018:ffffffff8c807d88 EFLAGS: 000002c6
RAX: 4dae34477ee2e100 RBX: ffffffff8a395407 RCX: 4dae34477ee2e100
RDX: 0000000000000001 RSI: ffffffff8a8c1aa0 RDI: ffffffff8adf2060
RBP: ffffffff8c807ec0 R08: ffff8880b8e3580b R09: 1ffff110171c6b01
R10: dffffc0000000000 R11: ffffed10171c6b02 R12: 0000000000000000
R13: dffffc0000000000 R14: ffffffff8c8bc740 R15: 1ffffffff1900fbc
FS:  0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f896d9456b8 CR3: 000000007e581000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 default_idle_call+0x84/0xc0 kernel/sched/idle.c:109
 cpuidle_idle_call kernel/sched/idle.c:199 [inline]
 do_idle+0x250/0x680 kernel/sched/idle.c:323
 cpu_startup_entry+0x3f/0x60 kernel/sched/idle.c:422
 rest_init+0x2dc/0x300 init/main.c:745
 arch_call_rest_init+0xa/0xa init/main.c:904
 start_kernel+0x493/0x53c init/main.c:1151
 secondary_startup_64_no_verify+0xcf/0xdb
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 7556 Comm: syz.3.732 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:arch_atomic_read arch/x86/include/asm/atomic.h:29 [inline]
RIP: 0010:rcu_dynticks_curr_cpu_in_eqs include/linux/context_tracking.h:122 [inline]
RIP: 0010:rcu_is_watching+0x56/0xa0 kernel/rcu/tree.c:721
Code: f0 48 c1 e8 03 42 80 3c 38 00 74 08 4c 89 f7 e8 f0 0f 67 00 48 c7 c3 08 58 03 00 49 03 1e 48 89 d8 48 c1 e8 03 42 0f b6 04 38 <84> c0 75 2f 8b 03 65 ff 0d c5 fb 95 7e 74 0c 83 e0 04 c1 e8 02 5b
RSP: 0018:ffffc900001e0c50 EFLAGS: 00000802
RAX: 0000000000000000 RBX: ffff8880b8f35808 RCX: 24a13412cac52c00
RDX: ffff888027c33c00 RSI: ffffffff8adf2040 RDI: ffffffff8adf2000
RBP: dffffc0000000000 R08: dffffc0000000000 R09: 1ffffffff215fe48
R10: dffffc0000000000 R11: fffffbfff215fe49 R12: ffff888077bfcc58
R13: ffff888077d38a00 R14: ffffffff8c658988 R15: dffffc0000000000
FS:  00007f29af31e6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c3002f8 CR3: 000000005e0eb000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 rcu_read_lock include/linux/rcupdate.h:792 [inline]
 send_sigqueue+0xcb/0x610 kernel/signal.c:1977
 posix_timer_event kernel/time/posix-timers.c:360 [inline]
 posix_timer_fn+0x16a/0x3d0 kernel/time/posix-timers.c:386
 __run_hrtimer kernel/time/hrtimer.c:1751 [inline]
 __hrtimer_run_queues+0x54a/0xd50 kernel/time/hrtimer.c:1815
 hrtimer_interrupt+0x3c5/0x9c0 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:get_current arch/x86/include/asm/current.h:15 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x4/0x60 kernel/kcov.c:215
Code: 00 00 00 00 00 90 53 48 89 fb e8 17 00 00 00 48 8b 3d 80 b0 9d 0c 48 89 de 5b e9 c7 3e 50 00 00 00 cc cc 00 00 cc 48 8b 04 24 <65> 48 8b 0d 94 f3 7f 7e 65 8b 15 95 f3 7f 7e 81 e2 00 01 ff 00 74
RSP: 0018:ffffc9000337fed0 EFLAGS: 00000246
RAX: ffffffff81562518 RBX: ffffc9000337ff20 RCX: 0000000000080000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff888027c33c00
RBP: 0000000000000001 R08: ffffffff8e2029ef R09: 1ffffffff1c4053d
R10: dffffc0000000000 R11: fffffbfff1c4053e R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: ffff888027c33c00
 __task_pid_nr_ns+0x18/0x460 kernel/pid.c:494
 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: 0033:0x7f29ae396bd7
Code: 8d 3d bd 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:00007f29af31da48 EFLAGS: 00000206 ORIG_RAX: 0000000000000027
RAX: ffffffffffffffda RBX: 00007f29af31dbb0 RCX: 00007f29ae396bd7
RDX: 00007f29af31da80 RSI: 00007f29af31dbb0 RDI: 0000000000000021
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 00007f29ae616038 R14: 00007f29ae615fa0 R15: 00007ffd22450138
 </TASK>

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
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.