[Letux-kernel] v5.9-rc1 compile issue

[H. Nikolaus Schaller]

  CC      fs/exec.o - due to target missing
  CC      fs/pipe.o - due to target missing
  CC      fs/namei.o - due to target missing
  CC      fs/fcntl.o - due to target missing
  CC      fs/ioctl.o - due to target missing
  CC      fs/readdir.o - due to target missing
  CC      fs/select.o - due to target missing
  CC      fs/dcache.o - due to target missing
  CC      fs/dcache.o - due to target missing
In file included from ./include/linux/spinlock_types.h:13:0,
                 from ./include/linux/ratelimit_types.h:7,
                 from ./include/linux/ratelimit.h:5,
                 from fs/dcache.c:18:
./arch/arm/include/asm/spinlock_types.h:13:3: error: unknown type name 'u32'
   u32 slock;
   ^
./arch/arm/include/asm/spinlock_types.h:19:4: error: unknown type name 'u16'
    u16 owner;
    ^
./arch/arm/include/asm/spinlock_types.h:20:4: error: unknown type name 'u16'
    u16 next;
    ^
./arch/arm/include/asm/spinlock_types.h:29:2: error: unknown type name 'u32'
  u32 lock;
  ^
make[3]: *** [fs/dcache.o] Error 1
make[2]: *** [fs] Error 2
make[1]: *** [__build_one_by_one] Error 2
make: *** [__sub-make] Error 2

But:

iMac:master hns$ git diff v5.9-rc1 fs/dcache.c ./include/linux/spinlock_types.h ./include/linux/ratelimit_types.h ./include/linux/ratelimit.h ./arch/arm/include/asm/spinlock_types.h
iMac:master hns$

So none of the reported files has been changed by us...

And git diff v5.8 v5.9-rc1 fs/dcache.c ./include/linux/spinlock_types.h ./include/linux/ratelimit_types.h ./include/linux/ratelimit.h ./arch/arm/include/asm/spinlock_types.h
only shows code moved a little around.

It fails on ARM only. Neither MIPS nor ARM64.

Any ideas how to find the (now missing) #include?
From which header file should u16 and u32 come from?

BR and thanks,
Nikolaus