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BUG: KCSAN: data-race in perf_event_update_userpage / perf_event_update_userpage

write to 0xffff888114954008 of 4 bytes by task 5192 on cpu 0:
 perf_event_update_userpage+0x166/0x340 kernel/events/core.c:5672
 cpu_clock_event_add+0x11d/0x130 kernel/events/core.c:10228
 event_sched_in+0x888/0x1010 kernel/events/core.c:2516
 group_sched_in kernel/events/core.c:2552 [inline]
 merge_sched_in kernel/events/core.c:3632 [inline]
 visit_groups_merge+0xccc/0x1e00 kernel/events/core.c:3605
 ctx_flexible_sched_in kernel/events/core.c:3672 [inline]
 ctx_sched_in+0x30b/0x330 kernel/events/core.c:3717
 perf_event_sched_in kernel/events/core.c:2661 [inline]
 perf_event_context_sched_in kernel/events/core.c:3757 [inline]
 __perf_event_task_sched_in+0x2e0/0x440 kernel/events/core.c:3796
 perf_event_task_sched_in include/linux/perf_event.h:1199 [inline]
 finish_task_switch+0x195/0x270 kernel/sched/core.c:3295
 context_switch kernel/sched/core.c:3461 [inline]
 __schedule+0x3b4/0x580 kernel/sched/core.c:4215
 preempt_schedule_irq+0x55/0x90 kernel/sched/core.c:4473
 idtentry_exit_cond_resched+0x30/0x40 arch/x86/entry/common.c:663
 idtentry_exit_cond_rcu+0x2e/0x30 arch/x86/entry/common.c:710
 sysvec_apic_timer_interrupt+0xc6/0xd0 arch/x86/kernel/apic/apic.c:1091
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:585
 __x64_sys_clock_gettime+0x0/0x150 kernel/time/posix-timers.c:1067
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888114954008 of 4 bytes by task 5193 on cpu 1:
 perf_event_update_userpage+0x153/0x340 kernel/events/core.c:5672
 perf_mmap+0xb78/0xcf0 kernel/events/core.c:6150
 call_mmap include/linux/fs.h:1913 [inline]
 mmap_region+0xbd1/0x1330 mm/mmap.c:1772
 do_mmap+0x7c2/0xcf0 mm/mmap.c:1545
 do_mmap_pgoff include/linux/mm.h:2596 [inline]
 vm_mmap_pgoff+0xed/0x170 mm/util.c:506
 ksys_mmap_pgoff+0x342/0x3a0 mm/mmap.c:1595
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 5193 Comm: syz-executor.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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