Re: [tip:locking/core 19/28] include/linux/fs.h:1422:29: error: array type has incomplete element type 'struct percpu_rw_semaphore'

[Thomas Gleixner]

kbuild test robot <lkp@xxxxxxxxx> writes:
> All errors (new ones prefixed by >>):
>
>    In file included from include/linux/huge_mm.h:8,
>                     from include/linux/mm.h:567,
>                     from arch/m68k/include/asm/uaccess_no.h:8,
>                     from arch/m68k/include/asm/uaccess.h:3,
>                     from include/linux/uaccess.h:11,
>                     from include/linux/sched/task.h:11,
>                     from include/linux/sched/signal.h:9,
>                     from include/linux/rcuwait.h:6,
>                     from include/linux/percpu-rwsem.h:7,
>                     from kernel/locking/percpu-rwsem.c:6:
>>> include/linux/fs.h:1422:29: error: array type has incomplete element type 'struct percpu_rw_semaphore'
>     1422 |  struct percpu_rw_semaphore rw_sem[SB_FREEZE_LEVELS];
>          |                             ^~~~~~

Same problem as in the other architectures and same cure.

Thanks,

        tglx
---
Subject: m68knommu: Remove mm.h include from uaccess_no.h
From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Date: Sat, 21 Mar 2020 20:22:10 +0100

In file included
  from include/linux/huge_mm.h:8,
  from include/linux/mm.h:567,
  from arch/m68k/include/asm/uaccess_no.h:8,
  from arch/m68k/include/asm/uaccess.h:3,
  from include/linux/uaccess.h:11,
  from include/linux/sched/task.h:11,
  from include/linux/sched/signal.h:9,
  from include/linux/rcuwait.h:6,
  from include/linux/percpu-rwsem.h:7,
  from kernel/locking/percpu-rwsem.c:6:
 include/linux/fs.h:1422:29: error: array type has incomplete element type 'struct percpu_rw_semaphore'
    1422 |  struct percpu_rw_semaphore rw_sem[SB_FREEZE_LEVELS];

Removing the include of linux/mm.h from the uaccess header solves the problem
and various build tests of nommu configurations still work.

Fixes: 80fbaf1c3f29 ("rcuwait: Add @state argument to rcuwait_wait_event()")
Reported-by: kbuild test robot <lkp@xxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Greg Ungerer <gerg@xxxxxxxxxxxxxx>
Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Cc: linux-m68k@xxxxxxxxxxxxxxxxxxxx
---
 arch/m68k/include/asm/uaccess_no.h |    1 -
 1 file changed, 1 deletion(-)

--- a/arch/m68k/include/asm/uaccess_no.h
+++ b/arch/m68k/include/asm/uaccess_no.h
@@ -5,7 +5,6 @@
 /*
  * User space memory access functions
  */
-#include <linux/mm.h>
 #include <linux/string.h>
 
 #include <asm/segment.h>