分类： LINUX
2012-05-23 23:22:06
关于kref的操作函数
初始化
void kref_init(struct kref *kref) { atomic_set(&kref->refcount, 1); smp_mb(); } |
注意smp_mb以及smp_mb_*的目的是保证在多核SMP机器上的一致性，初始化后引用计数为1。
递增引用计数
void kref_get(struct kref *kref) { WARN_ON(!atomic_read(&kref->refcount)); atomic_inc(&kref->refcount); smp_mb__after_atomic_inc(); } |
递减引用计数
int kref_put(struct kref *kref, void (*release)(struct kref *kref)) { WARN_ON(release == NULL); WARN_ON(release == (void (*)(struct kref *))kfree); if (atomic_dec_and_test(&kref->refcount)) { release(kref); return 1; } return 0; } |
kref_put使用了回调函数机制。如果引用计数递减后为0，将调用函数release来执行一些释放操作。函数kref_sub与本函数类似，只是kref_sub中引用计数可以减小指定的值，不再局限于1。
int kref_sub(struct kref *kref, unsigned int count, void (*release)(struct kref *kref)) { WARN_ON(release == NULL); WARN_ON(release == (void (*)(struct kref *))kfree); if (atomic_sub_and_test((int) count, &kref->refcount)) { release(kref); return 1; } return 0; } |
关于kobject的函数
初始化
void kobject_init(struct kobject *kobj, struct kobj_type *ktype) { char *err_str; if (!kobj) { err_str = "invalid kobject pointer!"; goto error; } if (!ktype) { err_str = "must have a ktype to be initialized properly!\n"; goto error; } if (kobj->state_initialized) { /* do not error out as sometimes we can recover */ printk(KERN_ERR "kobject (%p): tried to init an initialized " "object, something is seriously wrong.\n", kobj); dump_stack(); } kobject_init_internal(kobj); kobj->ktype = ktype; return; //内核中经常使用goto语句进行错误处理 error: printk(KERN_ERR "kobject (%p): %s\n", kobj, err_str); dump_stack(); } EXPORT_SYMBOL(kobject_init); |
kobj和ktype之间的映射关系。
static void kobject_init_internal(struct kobject *kobj) { if (!kobj) return; kref_init(&kobj->kref); INIT_LIST_HEAD(&kobj->entry); kobj->state_in_sysfs = 0; kobj->state_add_uevent_sent = 0; kobj->state_remove_uevent_sent = 0; kobj->state_initialized = 1; } |
函数kobject_init_internal的主要工作就是初始化引用计数，链表元素以及各种状态标识。
添加，即将kobject加入驱动模型系统中进行管理
int kobject_add(struct kobject *kobj, struct kobject *parent, const char *fmt, ...) { va_list args; int retval; if (!kobj) return -EINVAL; if (!kobj->state_initialized) { printk(KERN_ERR "kobject '%s' (%p): tried to add an " "uninitialized object, something is seriously wrong.\n", kobject_name(kobj), kobj); dump_stack(); return -EINVAL; } va_start(args, fmt); retval = kobject_add_varg(kobj, parent, fmt, args); va_end(args); return retval; } EXPORT_SYMBOL(kobject_add); |
该函数也仅是进行了参数验证之后，就调用函数kobject_add_varg执行真正的具体工作。
static int kobject_add_varg(struct kobject *kobj, struct kobject *parent, const char *fmt, va_list vargs) { int retval; retval = kobject_set_name_vargs(kobj, fmt, vargs); if (retval) { printk(KERN_ERR "kobject: can not set name properly!\n"); return retval; } kobj->parent = parent; return kobject_add_internal(kobj); } |
这个函数先是设置了kobject的名字，最后建立kobj及其父节点之间的映射关系。
int kobject_set_name_vargs(struct kobject *kobj, const char *fmt, va_list vargs) { const char *old_name = kobj->name; char *s; if (kobj->name && !fmt) return 0; kobj->name = kvasprintf(GFP_KERNEL, fmt, vargs); if (!kobj->name) return -ENOMEM; /* e some of these buggers have '/' in the name ... */ /* 因为kobject如果通过sysfs导出到用户空间都对应一个目录，所以名称中不能包含‘/’字符 */ while ((s = strchr(kobj->name, '/'))) s[0] = '!'; kfree(old_name); return 0; } |
删除，即从驱动设备模型系统中去掉本kobject。
void kobject_del(struct kobject *kobj) { if (!kobj) return; sysfs_remove_dir(kobj); kobj->state_in_sysfs = 0; kobj_kset_leave(kobj); kobject_put(kobj->parent); kobj->parent = NULL; } |
该函数首先从sysfs中去掉响应的目录项，然后从所属kset中去掉本kobject，并修改父节点引用计数。
static void kobj_kset_leave(struct kobject *kobj) { if (!kobj->kset) return; spin_lock(&kobj->kset->list_lock); list_del_init(&kobj->entry); spin_unlock(&kobj->kset->list_lock); kset_put(kobj->kset); } |
在本函数中，将本kobject从kset的链表中摘下，调用kset_put函数（下面会有介绍）。
函数kobject_get用于递增kobject引用计数。
struct kobject *kobject_get(struct kobject *kobj) { if (kobj) kref_get(&kobj->kref); return kobj; } |
对应的，函数kobject_put用于递增kobject引用计数，如果kobject引用计数为0，则调用kobject_release。
void kobject_put(struct kobject *kobj) { if (kobj) { if (!kobj->state_initialized) WARN(1, KERN_WARNING "kobject: '%s' (%p): is not " "initialized, yet kobject_put() is being " "called.\n", kobject_name(kobj), kobj); kref_put(&kobj->kref, kobject_release); } } |
以下函数用于删除时的清理工作。
static void kobject_release(struct kref *kref) { kobject_cleanup(container_of(kref, struct kobject, kref)); } static void kobject_cleanup(struct kobject *kobj) { struct kobj_type *t = get_ktype(kobj); const char *name = kobj->name; pr_debug("kobject: '%s' (%p): %s\n", kobject_name(kobj), kobj, __func__); if (t && !t->release) pr_debug("kobject: '%s' (%p): does not have a release() " "function, it is broken and must be fixed.\n", kobject_name(kobj), kobj); /* send "remove" if the caller did not do it but sent "add" */ if (kobj->state_add_uevent_sent && !kobj->state_remove_uevent_sent) { pr_debug("kobject: '%s' (%p): auto cleanup 'remove' event\n", kobject_name(kobj), kobj); kobject_uevent(kobj, KOBJ_REMOVE); } /* remove from sysfs if the caller did not do it */ if (kobj->state_in_sysfs) { pr_debug("kobject: '%s' (%p): auto cleanup kobject_del\n", kobject_name(kobj), kobj); kobject_del(kobj); } if (t && t->release) { pr_debug("kobject: '%s' (%p): calling ktype release\n", kobject_name(kobj), kobj); t->release(kobj); } /* free name if we allocated it */ if (name) { pr_debug("kobject: '%s': free name\n", name); kfree(name); } } |
有关kset的函数操作
初始化
void kset_init(struct kset *k) { kobject_init_internal(&k->kobj); INIT_LIST_HEAD(&k->list); spin_lock_init(&k->list_lock); } |
本函数中初始化kset结构体内嵌的kobject，然后初始化链表以及自旋锁。由此可以看出，通过内嵌方式，可以实现面向对象中的继承机制。
注册
int kset_register(struct kset *k) { int err; if (!k) return -EINVAL; kset_init(k); err = kobject_add_internal(&k->kobj); if (err) return err; kobject_uevent(&k->kobj, KOBJ_ADD); return 0; } |
所谓注册，无非是将内嵌的kobject加入设备模型系统中，当然，还要想用户空间到处uevent事件。此处的kobject_add_internal值得一看，从这个函数中可以看出kobject父子节点以及所属kset之间的关系规则。
static int kobject_add_internal(struct kobject *kobj) { int error = 0; struct kobject *parent; if (!kobj) return -ENOENT; if (!kobj->name || !kobj->name[0]) { WARN(1, "kobject: (%p): attempted to be registered with empty " "name!\n", kobj); return -EINVAL; } parent = kobject_get(kobj->parent); /* join kset if set, use it as parent if we do not already have one */ if (kobj->kset) { if (!parent) parent = kobject_get(&kobj->kset->kobj); kobj_kset_join(kobj); kobj->parent = parent; } pr_debug("kobject: '%s' (%p): %s: parent: '%s', set: '%s'\n", kobject_name(kobj), kobj, __func__, parent ? kobject_name(parent) : " kobj->kset ? kobject_name(&kobj->kset->kobj) : " error = create_dir(kobj); if (error) { kobj_kset_leave(kobj); kobject_put(parent); kobj->parent = NULL; /* be noisy on error issues */ if (error == -EEXIST) printk(KERN_ERR "%s failed for %s with " "-EEXIST, don't try to register things with " "the same name in the same directory.\n", __func__, kobject_name(kobj)); else printk(KERN_ERR "%s failed for %s (%d)\n", __func__, kobject_name(kobj), error); dump_stack(); } else kobj->state_in_sysfs = 1; return error; } |
由函数中可以看出，如果kobject的所属kset设定，而其父节点没有设定，则将本kobject加入kset，并将kset作为作为本kobject的父节点。
注销
void kset_unregister(struct kset *k) { if (!k) return; kobject_put(&k->kobj); } |
仅仅是减少内嵌kobject对象的引用计数
kobject和kset
将某一kobject加入kset
static void kobj_kset_join(struct kobject *kobj) { if (!kobj->kset) return; kset_get(kobj->kset); spin_lock(&kobj->kset->list_lock); list_add_tail(&kobj->entry, &kobj->kset->list); spin_unlock(&kobj->kset->list_lock); } |
将某一Kobject从kset中移除
static void kobj_kset_leave(struct kobject *kobj) { if (!kobj->kset) return; spin_lock(&kobj->kset->list_lock); list_del_init(&kobj->entry); spin_unlock(&kobj->kset->list_lock); kset_put(kobj->kset); } |
此处仅仅讲解了一些静态数据的操作函数，相应的动态数据操作类似，仅仅是数据不再是静态生命，而是动态创建。
注：在内核中经常可以看到某些函数参数和返回值相同，不光类型，也包括值，这样的做法是为了保证代码调用上的一致性，并没有什么特别作用。
