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BUG: KCSAN: data-race in d_alloc_parallel / d_set_d_op

read to 0xffff88812449b480 of 4 bytes by task 7396 on cpu 1:
 d_wait_lookup fs/dcache.c:2500 [inline]
 d_alloc_parallel+0x8e9/0xea0 fs/dcache.c:2588
 lookup_open fs/namei.c:3137 [inline]
 do_last fs/namei.c:3314 [inline]
 path_openat+0x1d3c/0x36e0 fs/namei.c:3525
 do_filp_open+0x11e/0x1b0 fs/namei.c:3555
 do_sys_open+0x3b3/0x4f0 fs/open.c:1097
 __do_sys_open fs/open.c:1115 [inline]
 __se_sys_open fs/open.c:1110 [inline]
 __x64_sys_open+0x55/0x70 fs/open.c:1110
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff88812449b480 of 4 bytes by task 7388 on cpu 0:
 d_set_d_op+0x17b/0x230 fs/dcache.c:1854
 proc_pident_instantiate+0x11e/0x170 fs/proc/base.c:2472
 proc_pident_lookup+0x146/0x160 fs/proc/base.c:2495
 proc_tgid_base_lookup+0x35/0x50 fs/proc/base.c:3124
 lookup_open fs/namei.c:3203 [inline]
 do_last fs/namei.c:3314 [inline]
 path_openat+0x15b6/0x36e0 fs/namei.c:3525
 do_filp_open+0x11e/0x1b0 fs/namei.c:3555
 do_sys_open+0x3b3/0x4f0 fs/open.c:1097
 __do_sys_open fs/open.c:1115 [inline]
 __se_sys_open fs/open.c:1110 [inline]
 __x64_sys_open+0x55/0x70 fs/open.c:1110
 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: 7388 Comm: ps Not tainted 5.4.0-rc3+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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