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BUG: KCSAN: data-race in d_alloc_parallel / d_set_d_op

read-write to 0xffff888149a43f00 of 4 bytes by task 15141 on cpu 0:
 d_set_d_op+0xf4/0x1e0 fs/dcache.c:1931
 proc_pident_instantiate+0x164/0x180 fs/proc/base.c:2652
 proc_pident_lookup+0x112/0x180 fs/proc/base.c:2675
 proc_tgid_base_lookup+0x2b/0x30 fs/proc/base.c:3387
 __lookup_slow+0x17a/0x230 fs/namei.c:1694
 lookup_slow+0x3c/0x60 fs/namei.c:1711
 walk_component fs/namei.c:2002 [inline]
 link_path_walk+0x648/0x7e0 fs/namei.c:2329
 path_openat+0x1a0/0x1d70 fs/namei.c:3775
 do_filp_open+0xf6/0x200 fs/namei.c:3809
 do_sys_openat2+0xab/0x110 fs/open.c:1437
 do_sys_open fs/open.c:1452 [inline]
 __do_sys_openat fs/open.c:1468 [inline]
 __se_sys_openat fs/open.c:1463 [inline]
 __x64_sys_openat+0xf3/0x120 fs/open.c:1463
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff888149a43f00 of 4 bytes by task 15140 on cpu 1:
 d_in_lookup include/linux/dcache.h:360 [inline]
 d_wait_lookup fs/dcache.c:2618 [inline]
 d_alloc_parallel+0x621/0xc90 fs/dcache.c:2706
 __lookup_slow+0x8d/0x230 fs/namei.c:1679
 lookup_slow+0x3c/0x60 fs/namei.c:1711
 walk_component fs/namei.c:2002 [inline]
 link_path_walk+0x648/0x7e0 fs/namei.c:2329
 path_openat+0x1a0/0x1d70 fs/namei.c:3775
 do_filp_open+0xf6/0x200 fs/namei.c:3809
 do_sys_openat2+0xab/0x110 fs/open.c:1437
 do_sys_open fs/open.c:1452 [inline]
 __do_sys_openat fs/open.c:1468 [inline]
 __se_sys_openat fs/open.c:1463 [inline]
 __x64_sys_openat+0xf3/0x120 fs/open.c:1463
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x10000000 -> 0x1000000c

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 15140 Comm: syz-executor.4 Not tainted 6.7.0-rc6-syzkaller-00078-ga4aebe936554 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
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