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BUG: KCSAN: data-race in pcpu_alloc_noprof / pcpu_balance_workfn

read-write to 0xffffffff88be03ac of 4 bytes by task 4902 on cpu 0:
 pcpu_update_empty_pages mm/percpu.c:602 [inline]
 pcpu_chunk_populated mm/percpu.c:1531 [inline]
 pcpu_balance_populated mm/percpu.c:2062 [inline]
 pcpu_balance_workfn+0x94e/0xa60 mm/percpu.c:2212
 process_one_work kernel/workqueue.c:3229 [inline]
 process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3310
 worker_thread+0x51d/0x6f0 kernel/workqueue.c:3391
 kthread+0x1d1/0x210 kernel/kthread.c:389
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

read to 0xffffffff88be03ac of 4 bytes by task 17799 on cpu 1:
 pcpu_alloc_noprof+0x9b6/0x10a0 mm/percpu.c:1894
 perf_trace_event_reg kernel/trace/trace_event_perf.c:121 [inline]
 perf_trace_event_init+0x4d9/0x7c0 kernel/trace/trace_event_perf.c:202
 perf_trace_init+0x159/0x1d0 kernel/trace/trace_event_perf.c:226
 perf_tp_event_init+0x67/0xd0 kernel/events/core.c:10357
 perf_try_init_event+0xcb/0x4f0 kernel/events/core.c:11891
 perf_init_event kernel/events/core.c:11977 [inline]
 perf_event_alloc+0xaca/0x1750 kernel/events/core.c:12259
 __do_sys_perf_event_open kernel/events/core.c:12766 [inline]
 __se_sys_perf_event_open+0x840/0x21f0 kernel/events/core.c:12657
 __x64_sys_perf_event_open+0x67/0x80 kernel/events/core.c:12657
 x64_sys_call+0x18d7/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:299
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000001 -> 0x00000004

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 17799 Comm: syz.1.6428 Not tainted 6.12.0-rc7-syzkaller-00192-gb5a24181e461 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/30/2024
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