arm linux kernel startkenal problem

I have been puzzled about the problem of start_kenal in the arm linux kernel for a long time but still can't solve it:

In include\linux\Cupmask.h, there are the following definitions
typedef struct { DECLARE_BITMAP(bits, NR_CPUS); } cpumask_t;
extern cpumask_t _unused_cpumask_arg_;

#define cpu_set(cpu, dst) __cpu_set((cpu), &(dst))
static inline void __cpu_set(int cpu, volatile cpumask_t *dstp)
{
set_bit(cpu, dstp->bits);
}

In include\linux\Types.h, there are the following definitions
#ifdef __KERNEL__
#define BITS_TO_LONGS(bits) \
(((bits)+BITS_PER_LONG-1)/BITS_PER_LONG)
#define DECLARE_BITMAP(name,bits) \
unsigned long name(this bits =32)
#define BITS_PER_BYTE 8
#endif

Problem with using single quotes in awk variables

We can conclude that: cpumask_t is equivalent to unsigned long bits
, so cpumask_t *dstp is a pointer to an unsigned long array.
Then why does this expression appear? set_bit(cpu, dstp->bits); ?????cpusets are represented by bit masks.
For an unsigned int type on a 32-bit machine, it has 32 bits. Then each bit corresponds to a CPU. For example, 0x1 represents the CPU at position 0. 0x3 represents the two CPUs at positions 0 and 1.

You can also look at the sixth post of this thread:
http://www.chinaunix.net/index.php?uid=20551201&url=http://linux.chinaunix.net/bbs/viewthread.php?tid=904906 Thanks to scutan (冬日夜雨) for his help (great guy),
I understand the meaning of the code better.

There is one thing I don't understand
static inline void __cpu_set(int cpu, volatile cpumask_t *dstp) //dest points to unsigned long bits
//I can't understand this expression dstp->bits
{
set_bit(cpuhttp://www.airmaxshoe.net, dstp->bits);
}-> It is generally used in data structures.
For example,
struct student
{
age;
heathy;
}

struct stdent *p;
If I want to access the age of *p, I can write p->age like this;

If you define an unsigned long aaa; unsigned long p; There is no such usage p->bit,,,,, I don't understand here. Original post by eezzrr at 2009-2-17 01:36 http://linux.chinaunix.net/bbs/images/common/back.gif
-> Generally used in data structures.
For example,
struct student
{
age;
heathy;
}

struct stdent *p;
If I want to access the age of *p, I can write p->age;

If you define an unsigned long aaa; unsigned long ...

is like this http://www.posercity.com, for example, unsigned long a, then a is the value of the first element of the array. And you can also use a, then a represents the first address of the array.