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BUG: KCSAN: data-race in __mod_timer / timer_clear_idle

write to 0xffff88812c01cb24 of 1 bytes by task 0 on cpu 0:
 timer_clear_idle+0x2e/0x40 kernel/time/timer.c:1687
 tick_nohz_idle_retain_tick+0x3e/0x40 kernel/time/tick-sched.c:1004
 cpuidle_idle_call kernel/sched/idle.c:210 [inline]
 do_idle+0x287/0x310 kernel/sched/idle.c:276
 cpu_startup_entry+0x15/0x20 kernel/sched/idle.c:372
 rest_init+0xd8/0xe0 init/main.c:705
 arch_call_rest_init+0xa/0xb
 start_kernel+0x608/0x6d0 init/main.c:1043
 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243

read to 0xffff88812c01cb24 of 1 bytes by task 8664 on cpu 1:
 forward_timer_base kernel/time/timer.c:900 [inline]
 __mod_timer+0xbd7/0x1020 kernel/time/timer.c:995
 mod_timer+0x1b/0x20 kernel/time/timer.c:1112
 sk_reset_timer+0x1f/0xa0 net/core/sock.c:2953
 tcp_send_delayed_ack+0x191/0x250 net/ipv4/tcp_output.c:3753
 __tcp_ack_snd_check+0x313/0x530 net/ipv4/tcp_input.c:5296
 tcp_rcv_established+0x12e2/0x1520 net/ipv4/tcp_input.c:5721
 tcp_v4_do_rcv+0x25e/0x480 net/ipv4/tcp_ipv4.c:1641
 sk_backlog_rcv include/net/sock.h:997 [inline]
 __release_sock+0xf5/0x260 net/core/sock.c:2550
 release_sock+0x40/0x110 net/core/sock.c:3066
 tcp_recvmsg+0x16ba/0x1c10 net/ipv4/tcp.c:2252
 inet_recvmsg+0xa9/0x210 net/ipv4/af_inet.c:845
 sock_recvmsg_nosec net/socket.c:886 [inline]
 sock_recvmsg net/socket.c:904 [inline]
 sock_read_iter+0x19c/0x1e0 net/socket.c:977
 call_read_iter include/linux/fs.h:1902 [inline]
 new_sync_read fs/read_write.c:415 [inline]
 vfs_read+0x523/0x590 fs/read_write.c:481
 ksys_read+0xce/0x180 fs/read_write.c:607
 __do_sys_read fs/read_write.c:617 [inline]
 __se_sys_read fs/read_write.c:615 [inline]
 __x64_sys_read+0x3e/0x50 fs/read_write.c:615
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 8664 Comm: syz-fuzzer Not tainted 5.8.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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