cpumask、cpumask_t 和 cpumask_var_t

1. 实验代码

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define NR_CPUS 32

#define BITS_PER_BYTE        8
#define BITS_PER_TYPE(type)    (sizeof(type) * BITS_PER_BYTE)
#define __KERNEL_DIV_ROUND_UP(n, d) (((n) + (d) - 1) / (d))
#define BITS_TO_LONGS(nr)    __KERNEL_DIV_ROUND_UP(nr, BITS_PER_TYPE(long))

//include/linux/types.h
#define DECLARE_BITMAP(name, bits) unsigned long name[BITS_TO_LONGS(bits)] //unsigned long bits[1];

//include/linux/cpumask.h
typedef struct cpumask { DECLARE_BITMAP(bits, NR_CPUS); } cpumask_t; //cpumask 和 cpumask_t 的定义
typedef struct cpumask cpumask_var_t[1]; //cpumask_var_t == struct cpumask[1]


/*

//编译预处理后：

struct cpumask {
    unsigned long bits[1]; 
}

cpumask_t == struct cpumask

cpumask_var_t == struct cpumask[1]

*/


static void cpumask_copy(struct cpumask *dstp, struct cpumask *srcp)
{
    memcpy(dstp, srcp, sizeof(*dstp));    
}

static void set_bit(int nr, unsigned long *addr)
{
    addr[nr / BITS_PER_TYPE(long)] |= 1UL << (nr % BITS_PER_TYPE(long));
}

static int test_bit(int nr, unsigned long *addr)
{
    return 1UL & (addr[nr / BITS_PER_TYPE(long)] >> (nr & (BITS_PER_TYPE(long)-1)));
}

static void cpumask_set_cpu(int cpu, struct cpumask *dstp)
{
    set_bit(cpu, dstp->bits);
}

static int cpumask_test_cpu(int cpu, struct cpumask *dstp)
{
    return test_bit(cpu, dstp->bits);
}

static void cpumask_clear(struct cpumask *dstp)
{
    memset(dstp->bits, 0, sizeof(dstp->bits));
}

static void struct_cpumask_test(int num)
{
    int i;
    struct cpumask mask;

    cpumask_clear(&mask);

    for (i = 0; i < num; i++) {
        cpumask_set_cpu(i, &mask);
    }

    printf("struct_cpumask mask=0x%lx\n", mask.bits[0]); //0xff
}

static void cpumask_t_test(int num)
{
    int i;
    cpumask_t t_mask;

    cpumask_clear(&t_mask);

    for (i = 0; i < num; i++) {
        cpumask_set_cpu(i, &t_mask);
    }

    printf("cpumask_t t_mask=0x%lx\n", t_mask.bits[0]); //0xff
}

static void cpumask_var_t_test(int num)
{
    int i;
    cpumask_var_t var_t_mask;

    cpumask_clear(var_t_mask); //没有&

    for (i = 0; i < num; i++) {
        cpumask_set_cpu(i, var_t_mask); //没有&
    }

    printf("cpumask_var_t var_t_mask=0x%lx\n", var_t_mask[0].bits[0]); //0xff
}


void main(int argc, char *argv[])
{
    int num = 8;

    if (argc == 2) {
        num = atoi(argv[1]);
    }

    struct_cpumask_test(num);
    cpumask_t_test(num);
    cpumask_var_t_test(num);
}

测试：

~/origin_tmp/8.cpumask$ gcc cpumask_test.c -o pp
~/origin_tmp/8.cpumask$ ./pp
struct_cpumask mask=0xff
cpumask_t t_mask=0xff
cpumask_var_t var_t_mask=0xff
~/origin_tmp/8.cpumask$ ./pp 1
struct_cpumask mask=0x1
cpumask_t t_mask=0x1
cpumask_var_t var_t_mask=0x1
~/origin_tmp/8.cpumask$ ./pp 2
struct_cpumask mask=0x3
cpumask_t t_mask=0x3
cpumask_var_t var_t_mask=0x3