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初始化

struct hlist_head {	struct hlist_node *first;};static struct hlist_head *pid_hash;static unsigned int pidhash_shift = 4;void __init pidhash_init(void){	int i, pidhash_size;	pid_hash = alloc_large_system_hash("PID", sizeof(*pid_hash), 0, 18,					   HASH_EARLY | HASH_SMALL,					   &pidhash_shift, NULL, 4096);	pidhash_size = 1 << pidhash_shift;	for (i = 0; i < pidhash_size; i++)		INIT_HLIST_HEAD(&pid_hash[i]);}

操作之添加元素

void attach_pid(struct task_struct *task, enum pid_type type,		struct pid *pid){	struct pid_link *link;	link = &task->pids[type];	link->pid = pid;	hlist_add_head_rcu(&link->node, &pid->tasks[type]);	=>static inline void hlist_add_head_rcu(struct hlist_node *n,					struct hlist_head *h)	{		struct hlist_node *first = h->first;		n->next = first;		n->pprev = &h->first;		rcu_assign_pointer(h->first, n);		if (first)			first->pprev = &n->next;	}}

根据进程号搜索进程

struct task_struct *find_task_by_vpid(pid_t vnr){	return find_task_by_pid_ns(vnr, task_active_pid_ns(current));	=>struct task_struct *find_task_by_pid_ns(pid_t nr, struct pid_namespace *ns)	{		return pid_task(find_pid_ns(nr, ns), PIDTYPE_PID);		=>struct pid *find_pid_ns(int nr, struct pid_namespace *ns)		{			struct hlist_node *elem;			struct upid *pnr;			hlist_for_each_entry_rcu(pnr, elem,					&pid_hash[pid_hashfn(nr, ns)], pid_chain)				if (pnr->nr == nr && pnr->ns == ns)					return container_of(pnr, struct pid,							numbers[ns->level]);				=>#define pid_hashfn(nr, ns)	hash_long((unsigned long)nr + (unsigned long)ns, pidhash_shift) // 2.6.34版本用哈希表, 4.16.3版本用基树了			return NULL;		}	}}

Linux内核 hlist_head/hlist_node结构解析

https://www.cnblogs.com/vinozly/p/5707166.html

Linux 内核 hlist 详解

https://blog.csdn.net/hs794502825/article/details/24597773/

Linux内核中哈希链表hlist_head

https://blog.csdn.net/hhhhhyyyyy8/article/details/102642220

Linux内核中的PID散列表实例

http://blog.chinaunix.net/uid-24227137-id-3630753.html