[v6.6] INFO: rcu detected stall in futex (2)
2 views
Skip to first unread message
syzbot
Oct 30, 2025, 9:02:29 PM (5 days ago) Oct 30
to syzkaller...@googlegroups.com
Hello,
syzbot found the following issue on:
HEAD commit: e5bbb12db2c7 Linux 6.6.115
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=178fbe7c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=12606d4b8832c7e4
dashboard link: https://syzkaller.appspot.com/bug?extid=aa74f9a1d1d8b3371105
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e6860876f0ec/disk-e5bbb12d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d6c28d7cc7f3/vmlinux-e5bbb12d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/8f52ba3964b2/bzImage-e5bbb12d.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+aa74f9...@syzkaller.appspotmail.com
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 1-...!: (1 GPs behind) idle=bd4c/1/0x4000000000000000 softirq=56260/56261 fqs=1
rcu: (detected by 0, t=10502 jiffies, g=64909, q=37 ncpus=2)
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 14443 Comm: syz.2.1793 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:get_current arch/x86/include/asm/current.h:41 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x8/0x60 kernel/kcov.c:215
Code: 00 00 f3 0f 1e fa 53 48 89 fb e8 13 00 00 00 48 8b 3d 0c fe c4 0c 48 89 de 5b e9 33 89 56 00 cc cc cc f3 0f 1e fa 48 8b 04 24 <65> 48 8b 0d 20 28 7e 7e 65 8b 15 21 28 7e 7e 81 e2 00 01 ff 00 74
RSP: 0018:ffffc900001f0bf8 EFLAGS: 00000086
RAX: ffffffff889dab86 RBX: ffff88801a2ce2c0 RCX: dffffc0000000000
RDX: ffff88805d760c00 RSI: ffff88805d760400 RDI: ffff88801a2ce2c0
RBP: ffff88805d760d50 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff5200003e17c R12: ffff88801a2ce340
R13: dffffc0000000000 R14: ffff88805d760400 R15: ffff88805d760c00
FS: 0000555576aa1500(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c32d958 CR3: 000000005b20a000 CR4: 00000000003506e0
Call Trace:
<IRQ>
taprio_set_budgets+0x26/0x390 net/sched/sch_taprio.c:675
advance_sched+0x964/0xc80 net/sched/sch_taprio.c:993
__run_hrtimer kernel/time/hrtimer.c:1750 [inline]
__hrtimer_run_queues+0x51e/0xc40 kernel/time/hrtimer.c:1814
hrtimer_interrupt+0x3c9/0x9c0 kernel/time/hrtimer.c:1876
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1077 [inline]
__sysvec_apic_timer_interrupt+0xfb/0x3b0 arch/x86/kernel/apic/apic.c:1094
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
sysvec_apic_timer_interrupt+0x9f/0xc0 arch/x86/kernel/apic/apic.c:1088
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:seqcount_lockdep_reader_access+0x17f/0x1c0 include/linux/seqlock.h:105
Code: 00 4d 85 e4 75 16 e8 d0 8f 0f 00 eb 15 e8 c9 8f 0f 00 e8 e4 cd f8 08 4d 85 e4 74 ea e8 ba 8f 0f 00 fb 48 c7 04 24 0e 36 e0 45 <4b> c7 04 3e 00 00 00 00 66 43 c7 44 3e 09 00 00 43 c6 44 3e 0b 00
RSP: 0018:ffffc9000e267d20 EFLAGS: 00000293
RAX: ffffffff8175ffd6 RBX: 0000000000000000 RCX: ffff888022bf8000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc9000e267dd0 R08: ffffffff8e4a8b6f R09: 1ffffffff1c9516d
R10: dffffc0000000000 R11: fffffbfff1c9516e R12: 0000000000000200
R13: 0000000002faf080 R14: 1ffff92001c4cfa4 R15: dffffc0000000000
timekeeping_get_delta kernel/time/timekeeping.c:254 [inline]
timekeeping_get_ns kernel/time/timekeeping.c:388 [inline]
ktime_get+0x7f/0x280 kernel/time/timekeeping.c:848
futex_init_timeout kernel/futex/syscalls.c:158 [inline]
__do_sys_futex kernel/futex/syscalls.c:177 [inline]
__se_sys_futex+0x2b2/0x3f0 kernel/futex/syscalls.c:164
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f29c2b8efc9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffeccfc5038 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: ffffffffffffffda RBX: 00000000000f085c RCX: 00007f29c2b8efc9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f29c2de618c
RBP: 0000000000000032 R08: 0000000000745d1e R09: 00000018ccfc532f
R10: 00007ffeccfc5130 R11: 0000000000000246 R12: 00007f29c2de618c
R13: 00007ffeccfc5130 R14: 00000000000f088e R15: 00007ffeccfc5150
</TASK>
rcu: rcu_preempt kthread starved for 10500 jiffies! g64909 f0x0 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:27192 pid:17 ppid:2 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5380 [inline]
__schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
schedule+0xbd/0x170 kernel/sched/core.c:6773
schedule_timeout+0x160/0x280 kernel/time/timer.c:2167
rcu_gp_fqs_loop+0x302/0x1560 kernel/rcu/tree.c:1667
rcu_gp_kthread+0x99/0x380 kernel/rcu/tree.c:1866
kthread+0x2fa/0x390 kernel/kthread.c:388
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
</TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 0 PID: 9542 Comm: kworker/u4:18 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Workqueue: events_unbound toggle_allocation_gate
RIP: 0010:csd_lock_wait kernel/smp.c:311 [inline]
RIP: 0010:smp_call_function_many_cond+0xde4/0x1130 kernel/smp.c:855
Code: 89 ee 83 e6 01 31 ff e8 da d6 0a 00 41 83 e5 01 49 bd 00 00 00 00 00 fc ff df 75 07 e8 15 d3 0a 00 eb 38 f3 90 42 0f b6 04 2b <84> c0 75 11 41 f7 04 24 01 00 00 00 74 1e e8 f9 d2 0a 00 eb e4 44
RSP: 0018:ffffc900037e7780 EFLAGS: 00000293
RAX: 0000000000000000 RBX: 1ffff110171e82ad RCX: ffff888076813c00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc900037e7900 R08: ffffffff90da8507 R09: 1ffffffff21b50a0
R10: dffffc0000000000 R11: fffffbfff21b50a1 R12: ffff8880b8f41568
R13: dffffc0000000000 R14: ffff8880b8e3d348 R15: 0000000000000001
FS: 0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000000cb30000 CR4: 00000000003506f0
Call Trace:
<TASK>
on_each_cpu_cond_mask+0x3f/0x80 kernel/smp.c:1022
on_each_cpu include/linux/smp.h:71 [inline]
text_poke_sync arch/x86/kernel/alternative.c:2222 [inline]
text_poke_bp_batch+0x318/0x930 arch/x86/kernel/alternative.c:2432
text_poke_flush arch/x86/kernel/alternative.c:2623 [inline]
text_poke_finish+0x30/0x50 arch/x86/kernel/alternative.c:2630
arch_jump_label_transform_apply+0x1c/0x30 arch/x86/kernel/jump_label.c:146
static_key_enable_cpuslocked+0x123/0x240 kernel/jump_label.c:207
static_key_enable+0x1a/0x20 kernel/jump_label.c:220
toggle_allocation_gate+0xaa/0x250 mm/kfence/core.c:831
process_one_work kernel/workqueue.c:2634 [inline]
process_scheduled_works+0xa45/0x15b0 kernel/workqueue.c:2711
worker_thread+0xa55/0xfc0 kernel/workqueue.c:2792
kthread+0x2fa/0x390 kernel/kthread.c:388
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
</TASK>
---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.
syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title
If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)
If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report
If you want to undo deduplication, reply with:
#syz undup
syzbot found the following issue on:
HEAD commit: e5bbb12db2c7 Linux 6.6.115
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=178fbe7c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=12606d4b8832c7e4
dashboard link: https://syzkaller.appspot.com/bug?extid=aa74f9a1d1d8b3371105
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e6860876f0ec/disk-e5bbb12d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d6c28d7cc7f3/vmlinux-e5bbb12d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/8f52ba3964b2/bzImage-e5bbb12d.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+aa74f9...@syzkaller.appspotmail.com
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 1-...!: (1 GPs behind) idle=bd4c/1/0x4000000000000000 softirq=56260/56261 fqs=1
rcu: (detected by 0, t=10502 jiffies, g=64909, q=37 ncpus=2)
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 14443 Comm: syz.2.1793 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:get_current arch/x86/include/asm/current.h:41 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x8/0x60 kernel/kcov.c:215
Code: 00 00 f3 0f 1e fa 53 48 89 fb e8 13 00 00 00 48 8b 3d 0c fe c4 0c 48 89 de 5b e9 33 89 56 00 cc cc cc f3 0f 1e fa 48 8b 04 24 <65> 48 8b 0d 20 28 7e 7e 65 8b 15 21 28 7e 7e 81 e2 00 01 ff 00 74
RSP: 0018:ffffc900001f0bf8 EFLAGS: 00000086
RAX: ffffffff889dab86 RBX: ffff88801a2ce2c0 RCX: dffffc0000000000
RDX: ffff88805d760c00 RSI: ffff88805d760400 RDI: ffff88801a2ce2c0
RBP: ffff88805d760d50 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff5200003e17c R12: ffff88801a2ce340
R13: dffffc0000000000 R14: ffff88805d760400 R15: ffff88805d760c00
FS: 0000555576aa1500(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c32d958 CR3: 000000005b20a000 CR4: 00000000003506e0
Call Trace:
<IRQ>
taprio_set_budgets+0x26/0x390 net/sched/sch_taprio.c:675
advance_sched+0x964/0xc80 net/sched/sch_taprio.c:993
__run_hrtimer kernel/time/hrtimer.c:1750 [inline]
__hrtimer_run_queues+0x51e/0xc40 kernel/time/hrtimer.c:1814
hrtimer_interrupt+0x3c9/0x9c0 kernel/time/hrtimer.c:1876
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1077 [inline]
__sysvec_apic_timer_interrupt+0xfb/0x3b0 arch/x86/kernel/apic/apic.c:1094
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
sysvec_apic_timer_interrupt+0x9f/0xc0 arch/x86/kernel/apic/apic.c:1088
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:seqcount_lockdep_reader_access+0x17f/0x1c0 include/linux/seqlock.h:105
Code: 00 4d 85 e4 75 16 e8 d0 8f 0f 00 eb 15 e8 c9 8f 0f 00 e8 e4 cd f8 08 4d 85 e4 74 ea e8 ba 8f 0f 00 fb 48 c7 04 24 0e 36 e0 45 <4b> c7 04 3e 00 00 00 00 66 43 c7 44 3e 09 00 00 43 c6 44 3e 0b 00
RSP: 0018:ffffc9000e267d20 EFLAGS: 00000293
RAX: ffffffff8175ffd6 RBX: 0000000000000000 RCX: ffff888022bf8000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc9000e267dd0 R08: ffffffff8e4a8b6f R09: 1ffffffff1c9516d
R10: dffffc0000000000 R11: fffffbfff1c9516e R12: 0000000000000200
R13: 0000000002faf080 R14: 1ffff92001c4cfa4 R15: dffffc0000000000
timekeeping_get_delta kernel/time/timekeeping.c:254 [inline]
timekeeping_get_ns kernel/time/timekeeping.c:388 [inline]
ktime_get+0x7f/0x280 kernel/time/timekeeping.c:848
futex_init_timeout kernel/futex/syscalls.c:158 [inline]
__do_sys_futex kernel/futex/syscalls.c:177 [inline]
__se_sys_futex+0x2b2/0x3f0 kernel/futex/syscalls.c:164
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f29c2b8efc9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffeccfc5038 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: ffffffffffffffda RBX: 00000000000f085c RCX: 00007f29c2b8efc9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f29c2de618c
RBP: 0000000000000032 R08: 0000000000745d1e R09: 00000018ccfc532f
R10: 00007ffeccfc5130 R11: 0000000000000246 R12: 00007f29c2de618c
R13: 00007ffeccfc5130 R14: 00000000000f088e R15: 00007ffeccfc5150
</TASK>
rcu: rcu_preempt kthread starved for 10500 jiffies! g64909 f0x0 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:27192 pid:17 ppid:2 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5380 [inline]
__schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
schedule+0xbd/0x170 kernel/sched/core.c:6773
schedule_timeout+0x160/0x280 kernel/time/timer.c:2167
rcu_gp_fqs_loop+0x302/0x1560 kernel/rcu/tree.c:1667
rcu_gp_kthread+0x99/0x380 kernel/rcu/tree.c:1866
kthread+0x2fa/0x390 kernel/kthread.c:388
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
</TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 0 PID: 9542 Comm: kworker/u4:18 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Workqueue: events_unbound toggle_allocation_gate
RIP: 0010:csd_lock_wait kernel/smp.c:311 [inline]
RIP: 0010:smp_call_function_many_cond+0xde4/0x1130 kernel/smp.c:855
Code: 89 ee 83 e6 01 31 ff e8 da d6 0a 00 41 83 e5 01 49 bd 00 00 00 00 00 fc ff df 75 07 e8 15 d3 0a 00 eb 38 f3 90 42 0f b6 04 2b <84> c0 75 11 41 f7 04 24 01 00 00 00 74 1e e8 f9 d2 0a 00 eb e4 44
RSP: 0018:ffffc900037e7780 EFLAGS: 00000293
RAX: 0000000000000000 RBX: 1ffff110171e82ad RCX: ffff888076813c00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc900037e7900 R08: ffffffff90da8507 R09: 1ffffffff21b50a0
R10: dffffc0000000000 R11: fffffbfff21b50a1 R12: ffff8880b8f41568
R13: dffffc0000000000 R14: ffff8880b8e3d348 R15: 0000000000000001
FS: 0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000000cb30000 CR4: 00000000003506f0
Call Trace:
<TASK>
on_each_cpu_cond_mask+0x3f/0x80 kernel/smp.c:1022
on_each_cpu include/linux/smp.h:71 [inline]
text_poke_sync arch/x86/kernel/alternative.c:2222 [inline]
text_poke_bp_batch+0x318/0x930 arch/x86/kernel/alternative.c:2432
text_poke_flush arch/x86/kernel/alternative.c:2623 [inline]
text_poke_finish+0x30/0x50 arch/x86/kernel/alternative.c:2630
arch_jump_label_transform_apply+0x1c/0x30 arch/x86/kernel/jump_label.c:146
static_key_enable_cpuslocked+0x123/0x240 kernel/jump_label.c:207
static_key_enable+0x1a/0x20 kernel/jump_label.c:220
toggle_allocation_gate+0xaa/0x250 mm/kfence/core.c:831
process_one_work kernel/workqueue.c:2634 [inline]
process_scheduled_works+0xa45/0x15b0 kernel/workqueue.c:2711
worker_thread+0xa55/0xfc0 kernel/workqueue.c:2792
kthread+0x2fa/0x390 kernel/kthread.c:388
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
</TASK>
---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.
syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title
If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)
If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report
If you want to undo deduplication, reply with:
#syz undup
Reply all
Reply to author
Forward
0 new messages