中断触发流程二

主要讲下两个结构体及其关系和在系统中所处的位置：

每一个中断线或者叫中断向量都对应一个desc结构体，系统中所有的desc组成一个结构体数组。

struct irq_desc {
        unsigned int            irq;
        struct timer_rand_state *timer_rand_state;
        unsigned int            *kstat_irqs;
#ifdef CONFIG_INTR_REMAP
        struct irq_2_iommu      *irq_2_iommu;
#endif
        irq_flow_handler_t      handle_irq;   //每个中断线都有一个中断处理程序
        struct irq_chip         *chip;        //包含一些中断开关  屏蔽等工作
        struct msi_desc         *msi_desc;
        void                    *handler_data;
        void                    *chip_data;
        struct irqaction        *action;        /* IRQ action list */   //中断子程序链表
        unsigned int            status;         /* IRQ status */        //说明这个中断线是否可以被共享

        unsigned int            depth;          /* nested irq disables */
        unsigned int            wake_depth;     /* nested wake enables */
        unsigned int            irq_count;      /* For detecting broken IRQs */
        unsigned long           last_unhandled; /* Aging timer for unhandled count */
        unsigned int            irqs_unhandled;
        spinlock_t              lock;
#ifdef CONFIG_SMP
        cpumask_var_t           affinity;
        unsigned int            node;
#ifdef CONFIG_GENERIC_PENDING_IRQ
        cpumask_var_t           pending_mask;
#endif
#endif
        atomic_t                threads_active;    //这里的线程是怎么回事呢？
        wait_queue_head_t       wait_for_threads;
#ifdef CONFIG_PROC_FS
        struct proc_dir_entry   *dir;
#endif
        const char              *name;
} ____cacheline_internodealigned_in_smp;

struct irq_chip {
        const char      *name;
        unsigned int    (*startup)(unsigned int irq);
        void            (*shutdown)(unsigned int irq);
        void            (*enable)(unsigned int irq);
        void            (*disable)(unsigned int irq);

        void            (*ack)(unsigned int irq);
        void            (*mask)(unsigned int irq);
        void            (*mask_ack)(unsigned int irq);
        void            (*unmask)(unsigned int irq);
        void            (*eoi)(unsigned int irq);

        void            (*end)(unsigned int irq);
        int             (*set_affinity)(unsigned int irq,
                                        const struct cpumask *dest);
        int             (*retrigger)(unsigned int irq);
        int             (*set_type)(unsigned int irq, unsigned int flow_type);
        int             (*set_wake)(unsigned int irq, unsigned int on);

        void            (*bus_lock)(unsigned int irq);
        void            (*bus_sync_unlock)(unsigned int irq);

        /* Currently used only by UML, might disappear one day.*/
#ifdef CONFIG_IRQ_RELEASE_METHOD
        void            (*release)(unsigned int irq, void *dev_id);
#endif
        /*
         * For compatibility, ->typename is copied into ->name.
         * Will disappear.
         */
        const char      *typename;
};

struct irqaction {    //每一个中断例程对应一个irqaction,都放在链表中
        irq_handler_t handler;   //这个结构体里面应该有指向中断子程序的指针
        unsigned long flags;
        const char *name;
        void *dev_id;    //在中断共享时用与区分中断子程序的
        struct irqaction *next;   //链表中指向下一个例程
        int irq;              //中断号
        struct proc_dir_entry *dir;
        irq_handler_t thread_fn;     //好奇怪  这里也有线程相关
        struct task_struct *thread;
        unsigned long thread_flags;
};