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BUG: KCSAN: data-race in calc_timer_values / perf_event_update_time

read to 0xffff888120c684d0 of 8 bytes by task 22857 on cpu 1:
 __perf_update_times kernel/events/core.c:623 [inline]
 calc_timer_values+0xb9/0x1d0 kernel/events/core.c:5340
 perf_event_update_userpage+0x7b/0x340 kernel/events/core.c:5395
 perf_mmap+0xe00/0xeb0 kernel/events/core.c:5877
 call_mmap include/linux/fs.h:1900 [inline]
 mmap_region+0x83c/0xd50 mm/mmap.c:1806
 do_mmap+0x6d4/0xba0 mm/mmap.c:1577
 do_mmap_pgoff include/linux/mm.h:2348 [inline]
 vm_mmap_pgoff+0x12d/0x190 mm/util.c:496
 ksys_mmap_pgoff+0x2d8/0x420 mm/mmap.c:1629
 __do_sys_mmap arch/x86/kernel/sys_x86_64.c:100 [inline]
 __se_sys_mmap arch/x86/kernel/sys_x86_64.c:91 [inline]
 __x64_sys_mmap+0x2e/0x40 arch/x86/kernel/sys_x86_64.c:91
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff888120c684d0 of 8 bytes by task 22651 on cpu 0:
 perf_event_update_time+0x19f/0x200 kernel/events/core.c:640
 perf_event_set_state.part.0+0x4a/0x100 kernel/events/core.c:657
 perf_event_set_state kernel/events/core.c:654 [inline]
 event_sched_out kernel/events/core.c:2101 [inline]
 event_sched_out.isra.0+0x228/0x540 kernel/events/core.c:2073
 group_sched_out.part.0+0x5c/0x140 kernel/events/core.c:2127
 group_sched_out kernel/events/core.c:2122 [inline]
 ctx_sched_out+0x568/0x5a0 kernel/events/core.c:3059
 task_ctx_sched_out+0x59/0x90 kernel/events/core.c:2500
 perf_event_context_sched_out kernel/events/core.c:3234 [inline]
 __perf_event_task_sched_out+0x544/0xaa0 kernel/events/core.c:3325
 perf_event_task_sched_out include/linux/perf_event.h:1167 [inline]
 prepare_task_switch kernel/sched/core.c:3157 [inline]
 context_switch kernel/sched/core.c:3336 [inline]
 __schedule+0x407/0x690 kernel/sched/core.c:4078
 schedule+0x47/0xd0 kernel/sched/core.c:4145
 freezable_schedule include/linux/freezer.h:172 [inline]
 futex_wait_queue_me+0x18d/0x290 kernel/futex.c:2627
 futex_wait+0x19b/0x3f0 kernel/futex.c:2733
 do_futex+0xe9/0x18d0 kernel/futex.c:3644
 __do_sys_futex kernel/futex.c:3705 [inline]
 __se_sys_futex kernel/futex.c:3673 [inline]
 __x64_sys_futex+0x2cd/0x3f0 kernel/futex.c:3673
 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: 22651 Comm: syz-executor.2 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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