[v5.15] INFO: rcu detected stall in sys_getpid (2)

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syzbot

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Nov 30, 2024, 4:19:30 PM11/30/24
to syzkaller...@googlegroups.com
Hello,

syzbot found the following issue on:

HEAD commit: 0a51d2d4527b Linux 5.15.173
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=17625f78580000
kernel config: https://syzkaller.appspot.com/x/.config?x=69147a3052c29ea2
dashboard link: https://syzkaller.appspot.com/bug?extid=4f1638fef5ef98110679
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm64
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=137480df980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/cbeb11c653b7/disk-0a51d2d4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3b646052737b/vmlinux-0a51d2d4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/0f7e7bafd5b2/Image-0a51d2d4.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4f1638...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 0-...!: (1 GPs behind) idle=0a3/1/0x4000000000000002 softirq=6298/6302 fqs=7
(t=10501 jiffies g=5557 q=337)
rcu: rcu_preempt kthread starved for 10487 jiffies! g5557 f0x0 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: 0 pid: 15 ppid: 2 flags:0x00000008
Call trace:
__switch_to+0x308/0x5e8 arch/arm64/kernel/process.c:518
context_switch kernel/sched/core.c:5027 [inline]
__schedule+0xf10/0x1e48 kernel/sched/core.c:6373
schedule+0x11c/0x1c8 kernel/sched/core.c:6456
schedule_timeout+0x1d8/0x344 kernel/time/timer.c:1914
rcu_gp_fqs_loop+0x26c/0x13d4 kernel/rcu/tree.c:1972
rcu_gp_kthread+0xc4/0x2c4 kernel/rcu/tree.c:2145
kthread+0x37c/0x45c kernel/kthread.c:334
ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:870
rcu: Stack dump where RCU GP kthread last ran:
Task dump for CPU 1:
task:syz.0.15 state:R running task stack: 0 pid: 4190 ppid: 4107 flags:0x00000000
Call trace:
__switch_to+0x308/0x5e8 arch/arm64/kernel/process.c:518
mark_usage kernel/locking/lockdep.c:4512 [inline]
__lock_acquire+0xc44/0x7638 kernel/locking/lockdep.c:4966
return_address+0x0/0x1ec
Task dump for CPU 0:
task:syz.3.25 state:R running task stack: 0 pid: 4188 ppid: 4123 flags:0x00000000
Call trace:
dump_backtrace+0x0/0x530 arch/arm64/kernel/stacktrace.c:152
show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:216
sched_show_task+0x43c/0x574 kernel/sched/core.c:8637
dump_cpu_task+0x84/0xa8 kernel/sched/core.c:10924
rcu_dump_cpu_stacks+0x2d8/0x540 kernel/rcu/tree_stall.h:350
print_cpu_stall+0x558/0xc7c kernel/rcu/tree_stall.h:633
check_cpu_stall kernel/rcu/tree_stall.h:727 [inline]
rcu_pending kernel/rcu/tree.c:3932 [inline]
rcu_sched_clock_irq+0xd20/0x1b8c kernel/rcu/tree.c:2619
update_process_times+0x1d4/0x270 kernel/time/timer.c:1818
tick_sched_handle kernel/time/tick-sched.c:254 [inline]
tick_sched_timer+0x340/0x4f8 kernel/time/tick-sched.c:1473
__run_hrtimer kernel/time/hrtimer.c:1688 [inline]
__hrtimer_run_queues+0x458/0xca4 kernel/time/hrtimer.c:1752
hrtimer_interrupt+0x2c0/0xb64 kernel/time/hrtimer.c:1814
timer_handler drivers/clocksource/arm_arch_timer.c:659 [inline]
arch_timer_handler_virt+0x74/0x88 drivers/clocksource/arm_arch_timer.c:670
handle_percpu_devid_irq+0x29c/0x7fc kernel/irq/chip.c:930
generic_handle_irq_desc include/linux/irqdesc.h:158 [inline]
handle_irq_desc kernel/irq/irqdesc.c:652 [inline]
handle_domain_irq+0xec/0x178 kernel/irq/irqdesc.c:707
gic_handle_irq+0x78/0x1c8 drivers/irqchip/irq-gic-v3.c:765
call_on_irq_stack+0x24/0x4c arch/arm64/kernel/entry.S:899
do_interrupt_handler+0x74/0x94 arch/arm64/kernel/entry-common.c:267
el1_interrupt+0x30/0x58 arch/arm64/kernel/entry-common.c:454
el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:470
el1h_64_irq+0x78/0x7c arch/arm64/kernel/entry.S:522
pid_nr_ns kernel/pid.c:479 [inline]
__task_pid_nr_ns+0x24c/0x420 kernel/pid.c:500
task_tgid_vnr include/linux/sched.h:1587 [inline]
__arm64_sys_getpid+0x20/0x30 kernel/sys.c:945
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
el0_svc+0x7c/0x1f0 arch/arm64/kernel/entry-common.c:608
el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:626
el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584


---
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syzbot

unread,
Sep 13, 2025, 4:07:34 AM9/13/25
to syzkaller...@googlegroups.com
syzbot has found a reproducer for the following issue on:

HEAD commit: 43bb85222e53 Linux 5.15.193
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1575eb62580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e1bb6d24ef2164eb
dashboard link: https://syzkaller.appspot.com/bug?extid=4f1638fef5ef98110679
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14fcf362580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11009b12580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/aa8fda38f146/disk-43bb8522.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5cfcd43783fc/vmlinux-43bb8522.xz
kernel image: https://storage.googleapis.com/syzbot-assets/582ede77e278/bzImage-43bb8522.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4f1638...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
(detected by 0, t=10502 jiffies, g=7681, q=310)
rcu: All QSes seen, last rcu_preempt kthread activity 10502 (4294957797-4294947295), jiffies_till_next_fqs=1, root ->qsmask 0x0
rcu: rcu_preempt kthread starved for 10502 jiffies! g7681 f0x2 RCU_GP_WAIT_FQS(5) ->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:27496 pid: 15 ppid: 2 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
schedule_timeout+0x15c/0x280 kernel/time/timer.c:1914
rcu_gp_fqs_loop+0x29e/0x11b0 kernel/rcu/tree.c:1972
rcu_gp_kthread+0x98/0x350 kernel/rcu/tree.c:2145
kthread+0x436/0x520 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>
rcu: Stack dump where RCU GP kthread last ran:
NMI backtrace for cpu 0
CPU: 0 PID: 4445 Comm: syz.1.33 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Call Trace:
<IRQ>
dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
nmi_cpu_backtrace+0x397/0x3d0 lib/nmi_backtrace.c:111
nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62
trigger_single_cpu_backtrace include/linux/nmi.h:166 [inline]
rcu_check_gp_kthread_starvation+0x1cd/0x250 kernel/rcu/tree_stall.h:487
print_other_cpu_stall+0x10c8/0x1220 kernel/rcu/tree_stall.h:592
check_cpu_stall kernel/rcu/tree_stall.h:745 [inline]
rcu_pending kernel/rcu/tree.c:3936 [inline]
rcu_sched_clock_irq+0x831/0x1110 kernel/rcu/tree.c:2619
update_process_times+0x193/0x200 kernel/time/timer.c:1818
tick_sched_handle kernel/time/tick-sched.c:254 [inline]
tick_sched_timer+0x37d/0x560 kernel/time/tick-sched.c:1473
__run_hrtimer kernel/time/hrtimer.c:1690 [inline]
__hrtimer_run_queues+0x4fe/0xc40 kernel/time/hrtimer.c:1754
hrtimer_interrupt+0x3bb/0x8d0 kernel/time/hrtimer.c:1816
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1097 [inline]
__sysvec_apic_timer_interrupt+0x137/0x4a0 arch/x86/kernel/apic/apic.c:1114
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
sysvec_apic_timer_interrupt+0x9b/0xc0 arch/x86/kernel/apic/apic.c:1108
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:lock_acquire+0x1f2/0x3f0 kernel/locking/lockdep.c:5627
Code: 00 9c 8f 84 24 80 00 00 00 f6 84 24 81 00 00 00 02 0f 85 f6 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 66 43 c7 44 3d 09 00 00 43 c6 44 3d 0b
RSP: 0018:ffffc900040dfda0 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: d8538ec39eb7c800
RDX: 0000000000000000 RSI: ffffffff8a0b2ac0 RDI: ffffffff8a59a480
RBP: ffffc900040dfec0 R08: dffffc0000000000 R09: fffffbfff1ff7819
R10: fffffbfff1ff7819 R11: 1ffffffff1ff7818 R12: ffffffff8c11c660
R13: 1ffff9200081bfc0 R14: 0000000000000246 R15: dffffc0000000000
rcu_lock_acquire+0x2a/0x30 include/linux/rcupdate.h:312
rcu_read_lock include/linux/rcupdate.h:739 [inline]
__task_pid_nr_ns+0x21/0x420 kernel/pid.c:497
task_tgid_vnr include/linux/sched.h:1585 [inline]
__ia32_sys_getpid+0x19/0x20 kernel/sys.c:945
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f24d8865b67
Code: 0b e9 68 fe ff ff 48 83 c4 18 48 8d 3d 32 6d d8 00 5b 5d 41 5c 41 5d 41 5e 41 5f e9 23 f8 fb ff 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 0f 1f 84 00 00
RSP: 002b:00007f24d7eddb08 EFLAGS: 00000202 ORIG_RAX: 0000000000000027
RAX: ffffffffffffffda RBX: 00007f24d7eddc70 RCX: 00007f24d8865b67
RDX: 00007f24d7eddb40 RSI: 00007f24d7eddc70 RDI: 0000000000000021
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000
R13: 00007f24d8ab6038 R14: 00007ffdc76e5210 R15: 00007ffdc76e52f8
</TASK>


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