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BUG: KCSAN: data-race in pcpu_alloc / pcpu_free_area

write to 0xffffffff8454374c of 4 bytes by task 1705 on cpu 1:
 pcpu_update_empty_pages mm/percpu.c:559 [inline]
 pcpu_block_update_hint_free mm/percpu.c:994 [inline]
 pcpu_free_area+0x531/0x5e0 mm/percpu.c:1254
 free_percpu+0x1d2/0x690 mm/percpu.c:2102
 perf_trace_event_unreg+0x193/0x1d0 kernel/trace/trace_event_perf.c:175
 perf_trace_destroy+0x59/0x70 kernel/trace/trace_event_perf.c:243
 tp_perf_event_destroy+0x11/0x20 kernel/events/core.c:9587
 _free_event+0x7db/0x9a0 kernel/events/core.c:4863
 put_event kernel/events/core.c:4957 [inline]
 perf_event_release_kernel+0x98c/0xa00 kernel/events/core.c:5072
 perf_release+0x21/0x30 kernel/events/core.c:5082
 __fput+0x25b/0x4e0 fs/file_table.c:280
 ____fput+0x11/0x20 fs/file_table.c:313
 task_work_run+0xae/0x130 kernel/task_work.c:140
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:174 [inline]
 exit_to_user_mode_prepare+0x151/0x170 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 0xffffffff8454374c of 4 bytes by task 1719 on cpu 0:
 pcpu_alloc+0x9d6/0x1170 mm/percpu.c:1835
 __alloc_percpu_gfp+0x22/0x30 mm/percpu.c:1894
 percpu_ref_init+0x2c/0x210 lib/percpu-refcount.c:72
 io_ring_ctx_alloc fs/io_uring.c:1146 [inline]
 io_uring_create+0x1d8/0x17d0 fs/io_uring.c:9529
 io_uring_setup fs/io_uring.c:9629 [inline]
 __do_sys_io_uring_setup fs/io_uring.c:9635 [inline]
 __se_sys_io_uring_setup fs/io_uring.c:9632 [inline]
 __x64_sys_io_uring_setup+0xe1/0x120 fs/io_uring.c:9632
 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: 0 PID: 1719 Comm: syz-executor.5 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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