Build error for nommu if CONFIG_DEBUG_ATOMIC_SLEEP is selected

[Axel Lin]

2013/10/18 Michael S. Tsirkin <mst at redhat.com>:
> On Fri, Oct 18, 2013 at 05:27:55PM +0800, Axel Lin wrote:
>> Hi Michael,
>>
>> I got below build error for nommu if CONFIG_DEBUG_ATOMIC_SLEEP is selected.
>> Also got the same build error if CONFIG_PROVE_LOCKING is selected.
>>
>> Seems this issue is introduced by commit 662bbcb2747c2
>> "mm, sched: Allow uaccess in atomic with pagefault_disable()".
>>
>> arch/arm/kernel/built-in.o: In function `arch_ptrace':
>> arch/arm/kernel/ptrace.c:852: undefined reference to `might_fault'
>> arch/arm/kernel/built-in.o: In function `restore_sigframe':
>> arch/arm/kernel/signal.c:173: undefined reference to `might_fault'
>> arch/arm/kernel/signal.c:174: undefined reference to `might_fault'
>> arch/arm/kernel/signal.c:175: undefined reference to `might_fault'
>> arch/arm/kernel/signal.c:176: undefined reference to `might_fault'
>> arch/arm/kernel/built-in.o:arch/arm/kernel/signal.c:177: more undefined references to `might_fault' follow
>> make: *** [vmlinux] Error 1
>>
>> Regards,
>> Axel
>
> Can you send/upload your full .config please?

I patch the kernel to port it for an arm7tdmi SoC.
But I think you can easily reproduce it by simply
select ARM7TDMI cpu and then enable either
CONFIG_DEBUG_ATOMIC_SLEEP or CONFIG_PROVE_LOCKING.

Note, might_fault is implemented in mm/memory.c which is not built if
!CONFIG_MMU.

Regards,
Axel