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BUG: KCSAN: data-race in mod_timer / timer_clear_idle

write to 0xffff88812bf1b6e4 of 1 bytes by task 0 on cpu 1:
 timer_clear_idle+0x42/0x50 kernel/time/timer.c:1675
 tick_nohz_restart_sched_tick kernel/time/tick-sched.c:839 [inline]
 __tick_nohz_idle_restart_tick+0x36/0x1b0 kernel/time/tick-sched.c:1140
 tick_nohz_idle_exit+0x1af/0x1e0 kernel/time/tick-sched.c:1181
 do_idle+0xb1/0x280 kernel/sched/idle.c:276
 cpu_startup_entry+0x1b/0x20 kernel/sched/idle.c:355
 start_secondary+0x208/0x260 arch/x86/kernel/smpboot.c:264
 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:241

read to 0xffff88812bf1b6e4 of 1 bytes by task 7148 on cpu 0:
 forward_timer_base kernel/time/timer.c:892 [inline]
 __mod_timer kernel/time/timer.c:983 [inline]
 mod_timer+0x50d/0x7a0 kernel/time/timer.c:1100
 sk_reset_timer+0x2d/0x70 net/core/sock.c:2838
 tcp_send_delayed_ack+0x21d/0x2b0 net/ipv4/tcp_output.c:3659
 __tcp_ack_snd_check+0x3d1/0x4f0 net/ipv4/tcp_input.c:5246
 tcp_rcv_established+0xce9/0xf50 net/ipv4/tcp_input.c:5672
 tcp_v4_do_rcv+0x381/0x4e0 net/ipv4/tcp_ipv4.c:1561
 sk_backlog_rcv include/net/sock.h:945 [inline]
 __release_sock+0x135/0x1e0 net/core/sock.c:2435
 release_sock+0x61/0x160 net/core/sock.c:2951
 tcp_recvmsg+0x63b/0x1a30 net/ipv4/tcp.c:2182
 inet_recvmsg+0xbb/0x250 net/ipv4/af_inet.c:838
 sock_recvmsg_nosec net/socket.c:871 [inline]
 sock_recvmsg net/socket.c:889 [inline]
 sock_recvmsg+0x92/0xb0 net/socket.c:885
 sock_read_iter+0x15f/0x1e0 net/socket.c:967
 call_read_iter include/linux/fs.h:1889 [inline]
 new_sync_read+0x389/0x4f0 fs/read_write.c:414

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 7148 Comm: syz-fuzzer Not tainted 5.4.0-rc3+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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