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BUG: KCSAN: data-race in do_wait / get_wchan

write to 0xffff888126fdb090 of 8 bytes by task 8108 on cpu 1:
 do_wait+0x1f9/0x4c0 kernel/exit.c:1490
 kernel_wait4+0x156/0x240 kernel/exit.c:1639
 __do_sys_wait4+0xea/0x100 kernel/exit.c:1651
 __se_sys_wait4 kernel/exit.c:1647 [inline]
 __x64_sys_wait4+0x5e/0x80 kernel/exit.c:1647
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888126fdb090 of 8 bytes by task 11106 on cpu 0:
 get_wchan+0x47/0x180 arch/x86/kernel/process.c:815
 do_task_stat+0xdf0/0x1370 fs/proc/array.c:522
 proc_tgid_stat+0x3d/0x60 fs/proc/array.c:632
 proc_single_show+0x89/0xe0 fs/proc/base.c:756
 seq_read+0x350/0x960 fs/seq_file.c:229
 __vfs_read+0x67/0xc0 fs/read_write.c:425
 vfs_read fs/read_write.c:461 [inline]
 vfs_read+0x143/0x2c0 fs/read_write.c:446
 ksys_read+0xd5/0x1b0 fs/read_write.c:587
 __do_sys_read fs/read_write.c:597 [inline]
 __se_sys_read fs/read_write.c:595 [inline]
 __x64_sys_read+0x4c/0x60 fs/read_write.c:595
 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: 11106 Comm: ps Not tainted 5.4.0-rc6+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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