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BUG: KCSAN: data-race in arch_perf_update_userpage / arch_perf_update_userpage

write to 0xffff8881025a2028 of 8 bytes by task 26638 on cpu 1:
 arch_perf_update_userpage+0x43/0x210 arch/x86/events/core.c:2311
 perf_event_update_userpage+0x273/0x340 kernel/events/core.c:5416
 cpu_clock_event_add+0x3d/0x60 kernel/events/core.c:9672
 event_sched_in.isra.0.part.0+0x1d5/0x560 kernel/events/core.c:2367
 event_sched_in kernel/events/core.c:2339 [inline]
 group_sched_in+0xd1/0x2c0 kernel/events/core.c:2403
 flexible_sched_in kernel/events/core.c:3418 [inline]
 flexible_sched_in+0x399/0x540 kernel/events/core.c:3407
 visit_groups_merge+0x1d9/0x320 kernel/events/core.c:3366
 ctx_flexible_sched_in kernel/events/core.c:3455 [inline]
 ctx_sched_in+0x1b4/0x360 kernel/events/core.c:3500
 perf_event_sched_in+0x77/0xb0 kernel/events/core.c:2512
 perf_event_context_sched_in kernel/events/core.c:3540 [inline]
 __perf_event_task_sched_in+0x354/0x390 kernel/events/core.c:3579
 perf_event_task_sched_in include/linux/perf_event.h:1150 [inline]
 finish_task_switch+0x108/0x260 kernel/sched/core.c:3221
 context_switch kernel/sched/core.c:3387 [inline]
 __schedule+0x319/0x640 kernel/sched/core.c:4069
 schedule+0x47/0xd0 kernel/sched/core.c:4136
 freezable_schedule include/linux/freezer.h:172 [inline]
 futex_wait_queue_me+0x18d/0x290 kernel/futex.c:2627

write to 0xffff8881025a2028 of 8 bytes by task 26639 on cpu 0:
 arch_perf_update_userpage+0x43/0x210 arch/x86/events/core.c:2311
 perf_event_update_userpage+0x273/0x340 kernel/events/core.c:5416
 perf_mmap+0xe00/0xeb0 kernel/events/core.c:5875
 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:2353 [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+0x91/0xc0 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

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 26639 Comm: syz-executor.5 Not tainted 5.4.0-rc3+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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