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BUG: KCSAN: data-race in event_sched_out / perf_event_update_userpage

write to 0xffff88812db198c8 of 8 bytes by task 20975 on cpu 0:
 __perf_update_times kernel/events/core.c:642 [inline]
 perf_event_update_time kernel/events/core.c:650 [inline]
 perf_event_set_state kernel/events/core.c:669 [inline]
 event_sched_out+0x315/0x7f0 kernel/events/core.c:2276
 group_sched_out+0xbf/0x1a0 kernel/events/core.c:2302
 ctx_sched_out+0x36f/0x410 kernel/events/core.c:3253
 task_ctx_sched_out kernel/events/core.c:2671 [inline]
 perf_event_context_sched_out kernel/events/core.c:3458 [inline]
 __perf_event_task_sched_out+0xc28/0xd30 kernel/events/core.c:3561
 perf_event_task_sched_out include/linux/perf_event.h:1227 [inline]
 prepare_task_switch+0x13d/0x140 kernel/sched/core.c:4124
 context_switch kernel/sched/core.c:4274 [inline]
 __schedule+0x374/0x5b0 kernel/sched/core.c:5073
 schedule+0x67/0x90 kernel/sched/core.c:5152
 exit_to_user_mode_loop kernel/entry/common.c:162 [inline]
 exit_to_user_mode_prepare+0xb6/0x170 kernel/entry/common.c:208
 __syscall_exit_to_user_mode_work kernel/entry/common.c:290 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:301
 do_syscall_64+0x40/0x50 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88812db198c8 of 8 bytes by task 20974 on cpu 1:
 __perf_update_times kernel/events/core.c:641 [inline]
 calc_timer_values kernel/events/core.c:5677 [inline]
 perf_event_update_userpage+0x107/0x2f0 kernel/events/core.c:5732
 perf_mmap+0xb6f/0xce0 kernel/events/core.c:6219
 call_mmap include/linux/fs.h:1982 [inline]
 mmap_region+0xbb6/0x13e0 mm/mmap.c:1805
 do_mmap+0x77d/0xc90 mm/mmap.c:1581
 vm_mmap_pgoff+0xfc/0x1d0 mm/util.c:519
 ksys_mmap_pgoff+0x2a8/0x380 mm/mmap.c:1632
 do_syscall_64+0x34/0x50 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 20974 Comm: syz-executor.0 Not tainted 5.12.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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