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BUG: KCSAN: data-race in d_alloc_parallel / d_set_d_op

write to 0xffff8881251d03c0 of 4 bytes by task 7738 on cpu 0:
 d_set_d_op+0x10c/0x230 fs/dcache.c:1850
 proc_pid_instantiate+0xdc/0x110 fs/proc/base.c:3238
 proc_fill_cache+0x1db/0x290 fs/proc/base.c:1900
 proc_pid_readdir+0x1c4/0x3ce fs/proc/base.c:3349
 proc_root_readdir+0x8f/0xb0 fs/proc/root.c:263
 iterate_dir+0x312/0x380 fs/readdir.c:65
 __do_sys_getdents fs/readdir.c:285 [inline]
 __se_sys_getdents fs/readdir.c:266 [inline]
 __x64_sys_getdents+0x14b/0x280 fs/readdir.c:266
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8881251d03c0 of 4 bytes by task 7736 on cpu 1:
 d_wait_lookup fs/dcache.c:2500 [inline]
 d_alloc_parallel+0x884/0xe00 fs/dcache.c:2588
 proc_fill_cache+0x182/0x290 fs/proc/base.c:1895
 proc_pid_readdir+0x1c4/0x3ce fs/proc/base.c:3349
 proc_root_readdir+0x8f/0xb0 fs/proc/root.c:263
 iterate_dir+0x312/0x380 fs/readdir.c:65
 __do_sys_getdents fs/readdir.c:285 [inline]
 __se_sys_getdents fs/readdir.c:266 [inline]
 __x64_sys_getdents+0x14b/0x280 fs/readdir.c:266
 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: 1 PID: 7736 Comm: ps Not tainted 5.4.0-rc7+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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