int count; //ary数组使用情况
int layer; //层号
struct rcu_head rcu_head;
};
[cpp]
#if BITS_PER_LONG == 32
# define IDR_BITS 5
# define IDR_FULL 0xfffffffful
# define TOP_LEVEL_FULL (IDR_FULL >> 30)
#elif BITS_PER_LONG == 64
# define IDR_BITS 6
# define IDR_FULL 0xfffffffffffffffful
# define TOP_LEVEL_FULL (IDR_FULL >> 62)
#else
# error "BITS_PER_LONG is not 32 or 64"
#endif
二.idr的初始化
[cpp]
#define IDR_INIT(name) \
{ \
.top = NULL, \
.id_free = NULL, \
.layers = 0, \
.id_free_cnt = 0, \
.lock = __SPIN_LOCK_UNLOCKED(name.lock), \
}
#define DEFINE_IDR(name) struct idr name = IDR_INIT(name)
定义一个idr结构体并赋值
三.分配id
1.idr_pre_get
[cpp]
int idr_pre_get(struct idr *idp, gfp_t gfp_mask)
{
while (idp->id_free_cnt < IDR_FREE_MAX) { //IDR_FREE_MAX=14
struct idr_layer *new; //定义新的idr_layer结构体指针
new = kmem_cache_zalloc(idr_layer_cache, gfp_mask); //分配*new内存空间
if (new == NULL)
return (0);
move_to_free_list(idp, new); //-->move_to_free_list
}
return 1;
}
EXPORT_SYMBOL(idr_pre_get);
move_to_free_list
[cpp]
static void move_to_free_list(struct idr *idp, struct idr_layer *p)
{
unsigned long flags;
spin_lock_irqsave(&idp->lock, flags);
__move_to_free_list(idp, p); //-->__move_to_free_list
spin_unlock_irqrestore(&idp->lock, flags);
}
__move_to_free_list
[cpp]
static void __move_to_free_list(struct idr *idp, struct idr_layer *p)
{
p->ary[0] = idp->id_free;
idp->id_free = p;
idp->id_free_cnt++;
}
第一次循环结果
接着循环
再接着
一直这样下去直到循环结束(14次)
2.idr_get_new和idr_get_new_above
idr_get_new
[cpp]
int idr_get_new(struct idr *idp, void *ptr, int *id)
{
int rv;
rv = idr_get_new_above_int(idp, ptr, 0);
if (rv < 0)
return _idr_rc_to_errno(rv);
*id = rv;
return 0;
}
EXPORT_SYMBOL(idr_get_new);
idr_get_new_above
[cpp]
int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id)
{
int rv;
rv = idr_get_new_above_int(idp, ptr, starting_id);
if (rv < 0)
return _idr_rc_to_errno(rv);
*id = rv;
return 0;
}
EXPORT_SYMBOL(idr_get_new_above);
两个函数都会调用idr_get_new_above_int函数,差别在于starting_id不同
下面分情况讨论,先以id为0走个过场
idr的top简称为根top,free简称为根free均为idr_layer指针类型,分别指向使用中和空闲idr_layer链表头
[cpp]
static int idr_get_new_above_int(struct idr *idp, void *ptr, int starting_id)
{
struct idr_layer *pa[MAX_LEVEL]; //MAX_LEVEL=7
int id;
id = idr_get_empty_slot(idp, starting_id, pa); //-->idr_get_empty_slot
if (id >= 0) {
rcu_assign_pointer(pa[0]->ary[id & IDR_MASK],(struct idr_layer *)ptr
//pa[
