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BUG: KCSAN: data-race in pcpu_balance_workfn / pcpu_nr_pages

read-write to 0xffffffff88bff2f8 of 8 bytes by task 3394 on cpu 1:
 pcpu_chunk_depopulated mm/percpu.c:1553 [inline]
 pcpu_reclaim_populated mm/percpu.c:2164 [inline]
 pcpu_balance_workfn+0x2c0/0xa60 mm/percpu.c:2211
 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 0xffffffff88bff2f8 of 8 bytes by task 7492 on cpu 0:
 pcpu_nr_pages+0x16/0x40 mm/percpu.c:3393
 meminfo_proc_show+0x937/0x9b0 fs/proc/meminfo.c:133
 seq_read_iter+0x2d1/0x930 fs/seq_file.c:230
 proc_reg_read_iter+0xec/0x190 fs/proc/inode.c:295
 copy_splice_read+0x3a0/0x5d0 fs/splice.c:365
 do_splice_read fs/splice.c:985 [inline]
 splice_direct_to_actor+0x269/0x670 fs/splice.c:1089
 do_splice_direct_actor fs/splice.c:1207 [inline]
 do_splice_direct+0xd7/0x150 fs/splice.c:1233
 do_sendfile+0x398/0x660 fs/read_write.c:1363
 __do_sys_sendfile64 fs/read_write.c:1424 [inline]
 __se_sys_sendfile64 fs/read_write.c:1410 [inline]
 __x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1410
 x64_sys_call+0xfbd/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:41
 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: 0x00000000000033c6 -> 0x00000000000033c5

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 7492 Comm: syz.0.6196 Not tainted 6.12.0-syzkaller-07834-g06afb0f36106 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/30/2024
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