Accessing memory causes system to freeze

I'm trying to read the values from memory of a process according to their vma's. However, whenever I try to access these locations en masse the system hangs and then crashes.

void print_mmap(struct vm_area_struct *mmap){         while (mmap != NULL)        {            printk(KERN_INFO "vm_start: %lu vm_end: %lu difference: %lu\n", mmap->vm_start, mmap->vm_end, (mmap->vm_end-mmap->vm_start));            int i;            for (i=0;mmap->vm_start<mmap->vm_end;i++)            {                (unsigned long*) (mmap->vm_start+i);            }            mmap = mmap->vm_next;        }}

Why would this happen? I use rcu_read_lock() and task_lock() prior to calling the function. If I print just one value or a few values from memory then the driver runs just fine, it appears to hang only when I access from beginning to end. Is there a better way of doing this?