[v6.1] INFO: rcu detected stall in __netif_receive_skb_core (2)
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syzbot
Jun 23, 2026, 11:33:28 PM (9 hours ago) Jun 23
to syzkaller...@googlegroups.com
Hello,
syzbot found the following issue on:
HEAD commit: fdb6fcb41cc7 Linux 6.1.176
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=13d1f6ae580000
kernel config: https://syzkaller.appspot.com/x/.config?x=acfbe65fbce84c0c
dashboard link: https://syzkaller.appspot.com/bug?extid=00c36a8c75318fc564ad
compiler: Debian clang version 22.1.6 (++20260514074242+fc4aad7b5db3-1~exp1~20260514074407.73), Debian LLD 22.1.6
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/8a12ae1ddcea/disk-fdb6fcb4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d0dd1b27df77/vmlinux-fdb6fcb4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/871bf60ea1f2/bzImage-fdb6fcb4.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+00c36a...@syzkaller.appspotmail.com
rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 1-.... } 4216 jiffies s: 3661 root: 0x2/.
rcu: blocking rcu_node structures (internal RCU debug):
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 4664 Comm: syz.9.33 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:check_region_inline mm/kasan/generic.c:-1 [inline]
RIP: 0010:kasan_check_range+0xe/0x290 mm/kasan/generic.c:189
Code: 0f 0b b8 ea ff ff ff c3 0f 0b b8 ea ff ff ff c3 00 00 cc cc 00 00 cc cc 00 00 cc cc b0 01 48 85 f6 0f 84 ac 01 00 00 55 41 57 <41> 56 41 54 53 49 89 f8 49 01 f0 0f 82 0e 02 00 00 49 89 f8 49 c1
RSP: 0018:ffffc900001dfda8 EFLAGS: 00000002
RAX: 0000000000000001 RBX: ffff88807f4f1e00 RCX: ffffffff8164ad54
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff90af2248
RBP: 0000000000000009 R08: dffffc0000000000 R09: 1ffffffff215e449
R10: dffffc0000000000 R11: fffffbfff215e44a R12: 0000000000000200
R13: dffffc0000000000 R14: ffff88807f4f2a20 R15: 0000000000000049
FS: 00007f27c4f7c6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f27c23d5990 CR3: 0000000065281000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<IRQ>
instrument_atomic_read include/linux/instrumented.h:72 [inline]
_test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
hlock_class kernel/locking/lockdep.c:228 [inline]
mark_lock+0x94/0x320 kernel/locking/lockdep.c:4606
mark_usage kernel/locking/lockdep.c:4549 [inline]
__lock_acquire+0xd83/0x7bd0 kernel/locking/lockdep.c:5003
lock_acquire+0x1bb/0x4a0 kernel/locking/lockdep.c:5662
seqcount_lockdep_reader_access+0xcd/0x1d0 include/linux/seqlock.h:102
ktime_get_update_offsets_now+0x44/0x3e0 kernel/time/timekeeping.c:2317
hrtimer_update_base kernel/time/hrtimer.c:652 [inline]
hrtimer_interrupt+0x11a/0x980 kernel/time/hrtimer.c:1859
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+0x4d/0xc0 arch/x86/kernel/apic/apic.c:1118
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:stack_trace_consume_entry+0x132/0x270 kernel/stacktrace.c:95
Code: 48 89 de 49 89 37 41 8b 18 41 0f b6 44 15 00 84 c0 0f 85 2f 01 00 00 41 3b 1e 0f 92 c0 48 83 c4 18 5b 41 5c 41 5d 41 5e 41 5f <5d> c3 44 89 c1 80 e1 07 80 c1 03 38 c1 0f 8c eb fe ff ff 48 89 fb
RSP: 0018:ffffc900001e04b8 EFLAGS: 00000296
RAX: 0000000000000001 RBX: ffffc900001e0580 RCX: 0000000000000100
RDX: dffffc0000000000 RSI: ffffffff8831b614 RDI: ffffc900001e0580
RBP: 1ffff9200003c0b2 R08: ffffc900001e0590 R09: 0000000000000006
R10: dffffc0000000000 R11: fffff5200003c0a5 R12: ffff88807f4f1e00
R13: ffffc900001e08e0 R14: ffffffff8170d250 R15: ffffc900001e04c8
arch_stack_walk+0x100/0x140 arch/x86/kernel/stacktrace.c:27
stack_trace_save+0xa6/0xf0 kernel/stacktrace.c:122
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
kasan_save_free_info+0x27/0x40 mm/kasan/generic.c:516
____kasan_slab_free+0x126/0x1f0 mm/kasan/common.c:237
kasan_slab_free include/linux/kasan.h:177 [inline]
slab_free_hook mm/slub.c:1729 [inline]
slab_free_freelist_hook+0x133/0x1b0 mm/slub.c:1755
slab_free mm/slub.c:3687 [inline]
kmem_cache_free+0xf7/0x2a0 mm/slub.c:3709
__netif_receive_skb_core+0x3217/0x38c0 net/core/dev.c:5593
__netif_receive_skb_one_core net/core/dev.c:5617 [inline]
__netif_receive_skb+0x74/0x290 net/core/dev.c:5733
process_backlog+0x37c/0x710 net/core/dev.c:6061
__napi_poll+0xbb/0x460 net/core/dev.c:6628
napi_poll net/core/dev.c:6695 [inline]
net_rx_action+0x622/0xbc0 net/core/dev.c:6809
handle_softirqs+0x291/0x910 kernel/softirq.c:596
__do_softirq kernel/softirq.c:630 [inline]
invoke_softirq kernel/softirq.c:470 [inline]
__irq_exit_rcu+0x13b/0x230 kernel/softirq.c:679
irq_exit_rcu+0x5/0x20 kernel/softirq.c:691
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
sysvec_apic_timer_interrupt+0xa0/0xc0 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:native_save_fl arch/x86/include/asm/irqflags.h:36 [inline]
RIP: 0010:arch_local_save_flags arch/x86/include/asm/irqflags.h:70 [inline]
RIP: 0010:arch_local_irq_save arch/x86/include/asm/irqflags.h:106 [inline]
RIP: 0010:rcu_read_unlock_special+0xe4/0x510 kernel/rcu/tree_plugin.h:640
Code: 5e 41 5f 5d c3 49 89 ff 42 c6 44 2b 08 00 48 c7 84 24 80 00 00 00 00 00 00 00 9c 8f 84 24 80 00 00 00 4c 8b a4 24 80 00 00 00 <42> c6 44 2b 08 f8 fa 41 f7 c4 00 02 00 00 74 0f e8 e7 9d 1b 00 66
RSP: 0018:ffffc900038d7420 EFLAGS: 00000246
RAX: f2f2f2f8f1f1f1f1 RBX: 1ffff9200071ae8c RCX: 0000000000080000
RDX: ffffc90013b56000 RSI: 000000000004d029 RDI: ffff88807f4f1e00
RBP: ffffc900038d7510 R08: ffff888019607b27 R09: 1ffff110032c0f64
R10: dffffc0000000000 R11: ffffed10032c0f65 R12: 0000000000000246
R13: dffffc0000000000 R14: 0000000000000002 R15: ffff88807f4f1e00
__rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:426
rcu_read_unlock include/linux/rcupdate.h:823 [inline]
page_ext_put+0x91/0xb0 mm/page_ext.c:182
page_table_check_pte_set include/linux/page_table_check.h:83 [inline]
set_pte_at arch/x86/include/asm/pgtable.h:1009 [inline]
copy_present_pte mm/memory.c:1000 [inline]
copy_pte_range mm/memory.c:1091 [inline]
copy_pmd_range mm/memory.c:1177 [inline]
copy_pud_range mm/memory.c:1214 [inline]
copy_p4d_range mm/memory.c:1238 [inline]
copy_page_range+0x2586/0x3a60 mm/memory.c:1332
dup_mmap kernel/fork.c:703 [inline]
dup_mm kernel/fork.c:1547 [inline]
copy_mm+0xeb0/0x1680 kernel/fork.c:1596
copy_process+0x19a6/0x40c0 kernel/fork.c:2357
kernel_clone+0x24b/0x900 kernel/fork.c:2764
__do_sys_clone kernel/fork.c:2905 [inline]
__se_sys_clone kernel/fork.c:2889 [inline]
__x64_sys_clone+0x1a7/0x220 kernel/fork.c:2889
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: 0033:0x7f27c419ce59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f27c4f7bfd8 EFLAGS: 00000206 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007f27c4415fa0 RCX: 00007f27c419ce59
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000002000000
RBP: 00007f27c4232e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 00007f27c4416038 R14: 00007f27c4415fa0 R15: 00007ffcda79f2b8
</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: fdb6fcb41cc7 Linux 6.1.176
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=13d1f6ae580000
kernel config: https://syzkaller.appspot.com/x/.config?x=acfbe65fbce84c0c
dashboard link: https://syzkaller.appspot.com/bug?extid=00c36a8c75318fc564ad
compiler: Debian clang version 22.1.6 (++20260514074242+fc4aad7b5db3-1~exp1~20260514074407.73), Debian LLD 22.1.6
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/8a12ae1ddcea/disk-fdb6fcb4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d0dd1b27df77/vmlinux-fdb6fcb4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/871bf60ea1f2/bzImage-fdb6fcb4.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+00c36a...@syzkaller.appspotmail.com
rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 1-.... } 4216 jiffies s: 3661 root: 0x2/.
rcu: blocking rcu_node structures (internal RCU debug):
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 4664 Comm: syz.9.33 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:check_region_inline mm/kasan/generic.c:-1 [inline]
RIP: 0010:kasan_check_range+0xe/0x290 mm/kasan/generic.c:189
Code: 0f 0b b8 ea ff ff ff c3 0f 0b b8 ea ff ff ff c3 00 00 cc cc 00 00 cc cc 00 00 cc cc b0 01 48 85 f6 0f 84 ac 01 00 00 55 41 57 <41> 56 41 54 53 49 89 f8 49 01 f0 0f 82 0e 02 00 00 49 89 f8 49 c1
RSP: 0018:ffffc900001dfda8 EFLAGS: 00000002
RAX: 0000000000000001 RBX: ffff88807f4f1e00 RCX: ffffffff8164ad54
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff90af2248
RBP: 0000000000000009 R08: dffffc0000000000 R09: 1ffffffff215e449
R10: dffffc0000000000 R11: fffffbfff215e44a R12: 0000000000000200
R13: dffffc0000000000 R14: ffff88807f4f2a20 R15: 0000000000000049
FS: 00007f27c4f7c6c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f27c23d5990 CR3: 0000000065281000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<IRQ>
instrument_atomic_read include/linux/instrumented.h:72 [inline]
_test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
hlock_class kernel/locking/lockdep.c:228 [inline]
mark_lock+0x94/0x320 kernel/locking/lockdep.c:4606
mark_usage kernel/locking/lockdep.c:4549 [inline]
__lock_acquire+0xd83/0x7bd0 kernel/locking/lockdep.c:5003
lock_acquire+0x1bb/0x4a0 kernel/locking/lockdep.c:5662
seqcount_lockdep_reader_access+0xcd/0x1d0 include/linux/seqlock.h:102
ktime_get_update_offsets_now+0x44/0x3e0 kernel/time/timekeeping.c:2317
hrtimer_update_base kernel/time/hrtimer.c:652 [inline]
hrtimer_interrupt+0x11a/0x980 kernel/time/hrtimer.c:1859
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+0x4d/0xc0 arch/x86/kernel/apic/apic.c:1118
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:stack_trace_consume_entry+0x132/0x270 kernel/stacktrace.c:95
Code: 48 89 de 49 89 37 41 8b 18 41 0f b6 44 15 00 84 c0 0f 85 2f 01 00 00 41 3b 1e 0f 92 c0 48 83 c4 18 5b 41 5c 41 5d 41 5e 41 5f <5d> c3 44 89 c1 80 e1 07 80 c1 03 38 c1 0f 8c eb fe ff ff 48 89 fb
RSP: 0018:ffffc900001e04b8 EFLAGS: 00000296
RAX: 0000000000000001 RBX: ffffc900001e0580 RCX: 0000000000000100
RDX: dffffc0000000000 RSI: ffffffff8831b614 RDI: ffffc900001e0580
RBP: 1ffff9200003c0b2 R08: ffffc900001e0590 R09: 0000000000000006
R10: dffffc0000000000 R11: fffff5200003c0a5 R12: ffff88807f4f1e00
R13: ffffc900001e08e0 R14: ffffffff8170d250 R15: ffffc900001e04c8
arch_stack_walk+0x100/0x140 arch/x86/kernel/stacktrace.c:27
stack_trace_save+0xa6/0xf0 kernel/stacktrace.c:122
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
kasan_save_free_info+0x27/0x40 mm/kasan/generic.c:516
____kasan_slab_free+0x126/0x1f0 mm/kasan/common.c:237
kasan_slab_free include/linux/kasan.h:177 [inline]
slab_free_hook mm/slub.c:1729 [inline]
slab_free_freelist_hook+0x133/0x1b0 mm/slub.c:1755
slab_free mm/slub.c:3687 [inline]
kmem_cache_free+0xf7/0x2a0 mm/slub.c:3709
__netif_receive_skb_core+0x3217/0x38c0 net/core/dev.c:5593
__netif_receive_skb_one_core net/core/dev.c:5617 [inline]
__netif_receive_skb+0x74/0x290 net/core/dev.c:5733
process_backlog+0x37c/0x710 net/core/dev.c:6061
__napi_poll+0xbb/0x460 net/core/dev.c:6628
napi_poll net/core/dev.c:6695 [inline]
net_rx_action+0x622/0xbc0 net/core/dev.c:6809
handle_softirqs+0x291/0x910 kernel/softirq.c:596
__do_softirq kernel/softirq.c:630 [inline]
invoke_softirq kernel/softirq.c:470 [inline]
__irq_exit_rcu+0x13b/0x230 kernel/softirq.c:679
irq_exit_rcu+0x5/0x20 kernel/softirq.c:691
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
sysvec_apic_timer_interrupt+0xa0/0xc0 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:native_save_fl arch/x86/include/asm/irqflags.h:36 [inline]
RIP: 0010:arch_local_save_flags arch/x86/include/asm/irqflags.h:70 [inline]
RIP: 0010:arch_local_irq_save arch/x86/include/asm/irqflags.h:106 [inline]
RIP: 0010:rcu_read_unlock_special+0xe4/0x510 kernel/rcu/tree_plugin.h:640
Code: 5e 41 5f 5d c3 49 89 ff 42 c6 44 2b 08 00 48 c7 84 24 80 00 00 00 00 00 00 00 9c 8f 84 24 80 00 00 00 4c 8b a4 24 80 00 00 00 <42> c6 44 2b 08 f8 fa 41 f7 c4 00 02 00 00 74 0f e8 e7 9d 1b 00 66
RSP: 0018:ffffc900038d7420 EFLAGS: 00000246
RAX: f2f2f2f8f1f1f1f1 RBX: 1ffff9200071ae8c RCX: 0000000000080000
RDX: ffffc90013b56000 RSI: 000000000004d029 RDI: ffff88807f4f1e00
RBP: ffffc900038d7510 R08: ffff888019607b27 R09: 1ffff110032c0f64
R10: dffffc0000000000 R11: ffffed10032c0f65 R12: 0000000000000246
R13: dffffc0000000000 R14: 0000000000000002 R15: ffff88807f4f1e00
__rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:426
rcu_read_unlock include/linux/rcupdate.h:823 [inline]
page_ext_put+0x91/0xb0 mm/page_ext.c:182
page_table_check_pte_set include/linux/page_table_check.h:83 [inline]
set_pte_at arch/x86/include/asm/pgtable.h:1009 [inline]
copy_present_pte mm/memory.c:1000 [inline]
copy_pte_range mm/memory.c:1091 [inline]
copy_pmd_range mm/memory.c:1177 [inline]
copy_pud_range mm/memory.c:1214 [inline]
copy_p4d_range mm/memory.c:1238 [inline]
copy_page_range+0x2586/0x3a60 mm/memory.c:1332
dup_mmap kernel/fork.c:703 [inline]
dup_mm kernel/fork.c:1547 [inline]
copy_mm+0xeb0/0x1680 kernel/fork.c:1596
copy_process+0x19a6/0x40c0 kernel/fork.c:2357
kernel_clone+0x24b/0x900 kernel/fork.c:2764
__do_sys_clone kernel/fork.c:2905 [inline]
__se_sys_clone kernel/fork.c:2889 [inline]
__x64_sys_clone+0x1a7/0x220 kernel/fork.c:2889
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: 0033:0x7f27c419ce59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f27c4f7bfd8 EFLAGS: 00000206 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007f27c4415fa0 RCX: 00007f27c419ce59
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000002000000
RBP: 00007f27c4232e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 00007f27c4416038 R14: 00007f27c4415fa0 R15: 00007ffcda79f2b8
</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
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