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BUG: KCSAN: data-race in d_alloc_parallel / d_set_d_op

read-write to 0xffff888120b54840 of 4 bytes by task 14362 on cpu 0:
 d_set_d_op+0xf4/0x1e0 fs/dcache.c:1932
 proc_pident_instantiate+0x164/0x180 fs/proc/base.c:2656
 proc_pident_lookup+0x112/0x180 fs/proc/base.c:2679
 proc_tgid_base_lookup+0x2b/0x30 fs/proc/base.c:3378
 __lookup_slow+0x17a/0x230 fs/namei.c:1690
 lookup_slow+0x3c/0x60 fs/namei.c:1707
 walk_component fs/namei.c:1998 [inline]
 link_path_walk+0x648/0x7e0 fs/namei.c:2325
 path_openat+0x1a1/0x1d10 fs/namei.c:3789
 do_filp_open+0xf6/0x200 fs/namei.c:3820
 do_sys_openat2+0xb5/0x2e0 fs/open.c:1402
 do_sys_open fs/open.c:1418 [inline]
 __do_sys_openat fs/open.c:1434 [inline]
 __se_sys_openat fs/open.c:1429 [inline]
 __x64_sys_openat+0xf3/0x120 fs/open.c:1429
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff888120b54840 of 4 bytes by task 14363 on cpu 1:
 d_in_lookup include/linux/dcache.h:359 [inline]
 d_wait_lookup fs/dcache.c:2619 [inline]
 d_alloc_parallel+0x621/0xc90 fs/dcache.c:2707
 __lookup_slow+0x8d/0x230 fs/namei.c:1675
 lookup_slow+0x3c/0x60 fs/namei.c:1707
 walk_component fs/namei.c:1998 [inline]
 link_path_walk+0x648/0x7e0 fs/namei.c:2325
 path_openat+0x1a1/0x1d10 fs/namei.c:3789
 do_filp_open+0xf6/0x200 fs/namei.c:3820
 do_sys_openat2+0xb5/0x2e0 fs/open.c:1402
 do_sys_open fs/open.c:1418 [inline]
 __do_sys_openat fs/open.c:1434 [inline]
 __se_sys_openat fs/open.c:1429 [inline]
 __x64_sys_openat+0xf3/0x120 fs/open.c:1429
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x10000000 -> 0x1000000c

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 14363 Comm: syz-executor.3 Not tainted 6.4.0-syzkaller-04247-g3a8a670eeeaa #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023
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