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BUG: KCSAN: data-race in add_timer_on / timer_clear_idle

write to 0xffff88812c11cb24 of 1 bytes by task 0 on cpu 1:
 timer_clear_idle+0x2e/0x40 kernel/time/timer.c:1686
 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
 start_secondary+0xe3/0x110 arch/x86/kernel/smpboot.c:268
 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243

read to 0xffff88812c11cb24 of 1 bytes by interrupt on cpu 0:
 forward_timer_base kernel/time/timer.c:899 [inline]
 add_timer_on+0x218/0x3b0 kernel/time/timer.c:1182
 clocksource_watchdog+0x729/0x760 kernel/time/clocksource.c:303
 call_timer_fn+0x30/0x2a0 kernel/time/timer.c:1415
 expire_timers+0x116/0x290 kernel/time/timer.c:1460
 __run_timers+0x443/0x500 kernel/time/timer.c:1784
 run_timer_softirq+0x2e/0x60 kernel/time/timer.c:1797
 __do_softirq+0x198/0x360 kernel/softirq.c:292
 run_ksoftirqd+0x2f/0x60 kernel/softirq.c:630
 smpboot_thread_fn+0x347/0x530 kernel/smpboot.c:165
 kthread+0x20d/0x230 kernel/kthread.c:291
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 9 Comm: ksoftirqd/0 Not tainted 5.8.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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