Raspberry Pi RT Preempt Linux Kernel Build Error

Question

I am trying to Build and install a Raspberry Pi RT Preempt Linux Kernel.

These are the steps that I had followed:

1. I installed the pre-compiled kernel kernel-4.4.9-rt17.tgz

2. I downloaded Raspberry Pi kernel sources and applied the Real Time patch-4.4.9-rt17.patch.gz.

3. I configured my kernel for Raspberry Pi3, Model B using:

   export KERNEL=kernel7
   make bcm2709_defconfig
   

4. I configured the kernel to support Fully Preemptible Kernel (RT) using

   make -j$(nproc) menuconfig
   

5. I built the kernel using

   make -j$(nproc) zImage 
   

   but I received the error:

   In file included from arch/arm/kernel/asm-offsets.c:14:0:
   ./include/linux/sched.h:2040:32: error: expected identifier or ‘(’ before ‘&’ token
   #define tsk_cpus_allowed(tsk) (&(tsk)->cpus_allowed)
                                   ^
   ./include/linux/sched.h:3679:37: note: in expansion of macro ‘tsk_cpus_allowed’
   static inline const struct cpumask *tsk_cpus_allowed(struct task_struct *p)
                                        ^
   In file included from arch/arm/kernel/asm-offsets.c:14:0:
   ./include/linux/sched.h:3687:19: error: redefinition of ‘tsk_nr_cpus_allowed’
    static inline int tsk_nr_cpus_allowed(struct task_struct *p)
                      ^
   In file included from arch/arm/kernel/asm-offsets.c:14:0:
   ./include/linux/sched.h:2042:19: note: previous definition of ‘tsk_nr_cpus_allowed’ was here
   

Here is the kernel build output

Do you have any idea to solve this? I don't know what I am doing wrong. I have been stuck at this for some time now and would really appreciate any help.