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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:1675
 tick_nohz_idle_retain_tick+0x3e/0x40 kernel/time/tick-sched.c:1004
 cpuidle_idle_call kernel/sched/idle.c:203 [inline]
 do_idle+0x290/0x320 kernel/sched/idle.c:269
 cpu_startup_entry+0x15/0x20 kernel/sched/idle.c:365
 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 8657 on cpu 1:
 forward_timer_base kernel/time/timer.c:891 [inline]
 __mod_timer+0xb87/0xf00 kernel/time/timer.c:983
 mod_timer+0x1b/0x20 kernel/time/timer.c:1100
 sk_reset_timer+0x1f/0xa0 net/core/sock.c:2951
 inet_csk_reset_xmit_timer include/net/inet_connection_sock.h:234 [inline]
 tcp_reset_xmit_timer include/net/tcp.h:1306 [inline]
 tcp_rearm_rto+0x204/0x210 net/ipv4/tcp_input.c:2998
 tcp_event_new_data_sent net/ipv4/tcp_output.c:81 [inline]
 tcp_write_xmit+0x1bee/0x3f30 net/ipv4/tcp_output.c:2524
 __tcp_push_pending_frames+0x68/0x1c0 net/ipv4/tcp_output.c:2692
 tcp_push+0x2c4/0x2e0 net/ipv4/tcp.c:733
 tcp_sendmsg_locked+0x1b90/0x2180 net/ipv4/tcp.c:1411
 tcp_sendmsg+0x2c/0x40 net/ipv4/tcp.c:1441
 inet_sendmsg+0x5f/0x80 net/ipv4/af_inet.c:814
 sock_sendmsg_nosec net/socket.c:652 [inline]
 sock_sendmsg net/socket.c:672 [inline]
 sock_write_iter+0x1a1/0x200 net/socket.c:999
 call_write_iter include/linux/fs.h:1907 [inline]
 new_sync_write fs/read_write.c:484 [inline]
 __vfs_write+0x2d8/0x340 fs/read_write.c:497
 vfs_write+0x19b/0x350 fs/read_write.c:559
 ksys_write+0xce/0x180 fs/read_write.c:612
 __do_sys_write fs/read_write.c:624 [inline]
 __se_sys_write fs/read_write.c:621 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:621
 do_syscall_64+0x71/0x120 arch/x86/entry/common.c:359
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 8657 Comm: syz-fuzzer Not tainted 5.8.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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