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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+0x168/0x1b0 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 7595 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:2842
 inet_csk_reset_xmit_timer include/net/inet_connection_sock.h:234 [inline]
 tcp_reset_xmit_timer include/net/tcp.h:1279 [inline]
 tcp_rearm_rto net/ipv4/tcp_input.c:3011 [inline]
 tcp_rearm_rto+0x1e7/0x2a0 net/ipv4/tcp_input.c:2987
 tcp_event_new_data_sent+0x218/0x220 net/ipv4/tcp_output.c:77
 tcp_write_xmit+0xa77/0x3120 net/ipv4/tcp_output.c:2447
 __tcp_push_pending_frames+0x7b/0x1d0 net/ipv4/tcp_output.c:2616
 tcp_push+0x1e9/0x3d0 net/ipv4/tcp.c:726
 tcp_sendmsg_locked+0x1d2b/0x1fb0 net/ipv4/tcp.c:1405
 tcp_sendmsg+0x39/0x60 net/ipv4/tcp.c:1436
 inet_sendmsg+0x6d/0x90 net/ipv4/af_inet.c:807
 sock_sendmsg_nosec net/socket.c:637 [inline]
 sock_sendmsg+0x9f/0xc0 net/socket.c:657
 sock_write_iter+0x16b/0x210 net/socket.c:989
 call_write_iter include/linux/fs.h:1895 [inline]
 new_sync_write+0x388/0x4a0 fs/read_write.c:483
 __vfs_write+0xb1/0xc0 fs/read_write.c:496
 vfs_write fs/read_write.c:558 [inline]
 vfs_write+0x18a/0x390 fs/read_write.c:542
 ksys_write+0xd5/0x1b0 fs/read_write.c:611
 __do_sys_write fs/read_write.c:623 [inline]
 __se_sys_write fs/read_write.c:620 [inline]
 __x64_sys_write+0x4c/0x60 fs/read_write.c:620
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 7595 Comm: syz-fuzzer Not tainted 5.4.0-rc7+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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