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BUG: KCSAN: data-race in get_cpu_idle_time_us / tick_irq_enter

write to 0xffff88812c11f1a8 of 8 bytes by task 0 on cpu 1:
 update_ts_time_stats kernel/time/tick-sched.c:554 [inline]
 tick_nohz_stop_idle kernel/time/tick-sched.c:564 [inline]
 tick_nohz_irq_enter kernel/time/tick-sched.c:1284 [inline]
 tick_irq_enter+0x14f/0x250 kernel/time/tick-sched.c:1303
 irq_enter_rcu+0x2d/0x60 kernel/softirq.c:359
 sysvec_apic_timer_interrupt+0x14/0xd0 arch/x86/kernel/apic/apic.c:1091
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:581
 native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:60
 arch_safe_halt arch/x86/include/asm/paravirt.h:150 [inline]
 acpi_safe_halt drivers/acpi/processor_idle.c:111 [inline]
 acpi_idle_do_entry drivers/acpi/processor_idle.c:524 [inline]
 acpi_idle_enter+0x30d/0x680 drivers/acpi/processor_idle.c:650
 cpuidle_enter_state+0x245/0x5d0 drivers/cpuidle/cpuidle.c:235
 cpuidle_enter+0x3c/0x60 drivers/cpuidle/cpuidle.c:346
 call_cpuidle kernel/sched/idle.c:126 [inline]
 cpuidle_idle_call kernel/sched/idle.c:214 [inline]
 do_idle+0x229/0x310 kernel/sched/idle.c:276
 cpu_startup_entry+0x15/0x20 kernel/sched/idle.c:372
 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243

read to 0xffff88812c11f1a8 of 8 bytes by task 11469 on cpu 0:
 get_cpu_idle_time_us+0x1d1/0x1f0 kernel/time/tick-sched.c:605
 get_idle_time fs/proc/stat.c:53 [inline]
 show_stat+0x24f/0xd10 fs/proc/stat.c:131
 seq_read+0x2ee/0x900 fs/seq_file.c:208
 pde_read fs/proc/inode.c:306 [inline]
 proc_reg_read+0xde/0x1a0 fs/proc/inode.c:316
 do_loop_readv_writev fs/read_write.c:734 [inline]
 do_iter_read+0x3d2/0x4b0 fs/read_write.c:955
 vfs_readv fs/read_write.c:1073 [inline]
 do_preadv+0x13b/0x230 fs/read_write.c:1165
 __do_sys_preadv fs/read_write.c:1215 [inline]
 __se_sys_preadv fs/read_write.c:1210 [inline]
 __x64_sys_preadv+0x54/0x60 fs/read_write.c:1210
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 11469 Comm: syz-executor.4 Not tainted 5.9.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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