本文簡單看看linux kernel 中的 hlist長什么樣

• API

// include/linux/types.h
struct hlist_head {
        struct hlist_node *first;
};

struct hlist_node {
        struct hlist_node *next, **pprev;
};

敲十幾遍記?。?/p>

#define DEFINE_HASHTABLE(name, bits)                        \
    struct hlist_head name[1 << (bits)] =                   \
            { [0 ... ((1 << (bits)) - 1)] = HLIST_HEAD_INIT }
            
#define HLIST_HEAD_INIT { .first = NULL }

解析上面兩個macro

DEFINE_HASHTABLE(htable, 3); 
// =>
struct hlist_head htable[8] = {[0 ... 7] = {.first=NULL} };


// 初始化一個hlist_head數(shù)組，大小為8，每個成員htable[i]初始化為：
htable[i] = {
    .first = NULL;
};

看看初始化后的樣子

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/hashtable.h>
#include <linux/vmalloc.h>

#define HBITS 3

DEFINE_HASHTABLE(test_htable, HBITS);

void hlist_t(void){
        char *buff, *pos;
        int i;

        buff = vmalloc(4096);
        if(!buff){
                pr_err("[!] vmalloc failed!\n");
                return;
        }

        pos = buff;

        for(i = 0; i < 1<<HBITS; i++){
                pos += sprintf(pos, "<%px> test_htable[%d].first: %px\n", &test_htable[i], i, test_htable[i].first);
        }

        pr_info("%s\n", buff);

        vfree(buff);

}

static int __init hlist_t_init(void)
{
    printk(KERN_INFO "Hello hlist_t\n");
    hlist_t();
    return 0;
}

static void __exit hlist_t_exit(void)
{
    printk(KERN_INFO "Goodbye hlist_t\n");
}


module_init(hlist_t_init);
module_exit(hlist_t_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("X++0");
MODULE_DESCRIPTION("Kernel xxx Module.");
MODULE_VERSION("0.1");

obj-m += hlist-t.o
KDIR := /lib/modules/$(shell uname -r)/build

all:
        make -C $(KDIR) M=$(PWD) modules

clean:
        @rm -rf *.o *.mod.c *.mod.o *.order *.symvers .*.cmd *.mod .tmp_versions

clean_all:
        @rm -rf *.o *.mod.c *.mod.o *.order *.symvers .*.cmd *.mod *.ko .tmp_versions

$ dmesg
...
[  412.576930] <ffffffffa0002340> test_htable[0].first: 0000000000000000
[  412.576930] <ffffffffa0002348> test_htable[1].first: 0000000000000000
[  412.576930] <ffffffffa0002350> test_htable[2].first: 0000000000000000
[  412.576930] <ffffffffa0002358> test_htable[3].first: 0000000000000000
[  412.576930] <ffffffffa0002360> test_htable[4].first: 0000000000000000
[  412.576930] <ffffffffa0002368> test_htable[5].first: 0000000000000000
[  412.576930] <ffffffffa0002370> test_htable[6].first: 0000000000000000
[  412.576930] <ffffffffa0002378> test_htable[7].first: 0000000000000000
...