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BUG: KCSAN: data-race in hrtimer_interrupt / print_cpu

read-write to 0xffff888237d1b8d8 of 4 bytes by interrupt on cpu 1:
 hrtimer_interrupt+0x5d/0x850 kernel/time/hrtimer.c:2091
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1050 [inline]
 __sysvec_apic_timer_interrupt+0x5f/0x1c0 arch/x86/kernel/apic/apic.c:1067
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1061 [inline]
 sysvec_apic_timer_interrupt+0x32/0x80 arch/x86/kernel/apic/apic.c:1061
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
 ip6_protocol_deliver_rcu+0xa6c/0x1170 net/ipv6/ip6_input.c:479
 ip6_input_finish+0xf0/0x1c0 net/ipv6/ip6_input.c:534
 NF_HOOK include/linux/netfilter.h:318 [inline]
 ip6_input+0x5e/0x160 net/ipv6/ip6_input.c:545
 dst_input include/net/dst.h:480 [inline]
 ip6_rcv_finish+0x1f5/0x330 net/ipv6/ip6_input.c:119
 NF_HOOK include/linux/netfilter.h:318 [inline]
 ipv6_rcv+0x72/0x170 net/ipv6/ip6_input.c:351
 __netif_receive_skb_one_core net/core/dev.c:6202 [inline]
 __netif_receive_skb net/core/dev.c:6315 [inline]
 process_backlog+0x2a5/0x670 net/core/dev.c:6666
 __napi_poll+0x61/0x300 net/core/dev.c:7733
 napi_poll net/core/dev.c:7796 [inline]
 net_rx_action+0x452/0x930 net/core/dev.c:7953
 handle_softirqs+0xb9/0x280 kernel/softirq.c:622
 do_softirq+0x45/0x60 kernel/softirq.c:523
 __local_bh_enable_ip+0x70/0x80 kernel/softirq.c:450
 local_bh_enable include/linux/bottom_half.h:33 [inline]
 rcu_read_unlock_bh include/linux/rcupdate.h:912 [inline]
 __dev_queue_xmit+0x1396/0x1ec0 net/core/dev.c:4905
 dev_queue_xmit include/linux/netdevice.h:3418 [inline]
 neigh_connected_output+0x253/0x2c0 net/core/neighbour.c:1648
 neigh_output include/net/neighbour.h:560 [inline]
 ip6_finish_output2+0x88e/0xd70 net/ipv6/ip6_output.c:136
 __ip6_finish_output net/ipv6/ip6_output.c:-1 [inline]
 ip6_finish_output+0x1e1/0x410 net/ipv6/ip6_output.c:219
 NF_HOOK_COND include/linux/netfilter.h:307 [inline]
 ip6_output+0x10a/0x280 net/ipv6/ip6_output.c:246
 dst_output include/net/dst.h:470 [inline]
 ip6_local_out+0x77/0xd0 net/ipv6/output_core.c:129
 ip6_send_skb net/ipv6/ip6_output.c:2018 [inline]
 ip6_push_pending_frames+0x7f/0x150 net/ipv6/ip6_output.c:2039
 rawv6_push_pending_frames+0x408/0x480 net/ipv6/raw.c:590
 rawv6_sendmsg+0x1136/0x1230 net/ipv6/raw.c:920
 inet_sendmsg+0xc5/0xd0 net/ipv4/af_inet.c:866
 sock_sendmsg_nosec net/socket.c:787 [inline]
 __sock_sendmsg net/socket.c:802 [inline]
 ____sys_sendmsg+0x519/0x5b0 net/socket.c:2698
 ___sys_sendmsg+0x195/0x1e0 net/socket.c:2752
 __sys_sendmsg net/socket.c:2784 [inline]
 __do_sys_sendmsg net/socket.c:2789 [inline]
 __se_sys_sendmsg net/socket.c:2787 [inline]
 __x64_sys_sendmsg+0xd4/0x160 net/socket.c:2787
 x64_sys_call+0x194c/0x3020 arch/x86/include/generated/asm/syscalls_64.h:47
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888237d1b8d8 of 4 bytes by task 8385 on cpu 0:
 print_cpu+0x346/0x670 kernel/time/timer_list.c:131
 timer_list_show+0x107/0x170 kernel/time/timer_list.c:291
 seq_read_iter+0x636/0x940 fs/seq_file.c:273
 proc_reg_read_iter+0x110/0x180 fs/proc/inode.c:299
 copy_splice_read+0x471/0x6c0 fs/splice.c:362
 do_splice_read fs/splice.c:980 [inline]
 splice_direct_to_actor+0x26e/0x670 fs/splice.c:1084
 do_splice_direct_actor fs/splice.c:1202 [inline]
 do_splice_direct+0x119/0x1a0 fs/splice.c:1228
 do_sendfile+0x382/0x650 fs/read_write.c:1372
 __do_sys_sendfile64 fs/read_write.c:1433 [inline]
 __se_sys_sendfile64 fs/read_write.c:1419 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1419
 x64_sys_call+0x2dc4/0x3020 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x000c4bd5 -> 0x000c4bd6

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 8385 Comm: syz.5.1575 Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
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