2010.10.8日课堂概念解析
关于中断的三个结构体：
中断控制器描述符irq_chip 和硬件相关
/**
* struct irq_chip - hardware interrupt chip descriptor
*
* @name: name for /proc/interrupts
* @startup: start up the interrupt (defaults to ->enable if NULL)
* @shutdown: shut down the interrupt (defaults to ->disable if NULL)
* @enable: enable the interrupt (defaults to chip->unmask if NULL)
* @disable: disable the interrupt
* @ack: start of a new interrupt
* @mask: mask an interrupt source
* @mask_ack: ack and mask an interrupt source
* @unmask: unmask an interrupt source
* @eoi: end of interrupt - chip level
* @end: end of interrupt - flow level
* @set_affinity: set the CPU affinity on SMP machines
* @retrigger: resend an IRQ to the CPU
* @set_type: set the flow type (IRQ_TYPE_LEVEL/etc.) of an IRQ
* @set_wake: enable/disable power-management wake-on of an IRQ
*
* @bus_lock: function to lock access to slow bus (i2c) chips
* @bus_sync_unlock: function to sync and unlock slow bus (i2c) chips
*
* @release: release function solely used by UML
* @typename: obsoleted by name, kept as migration helper
*/
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;
};
中断服务程序描述符 -- 软件实现
/**
* struct irqaction - per interrupt action descriptor
* @handler: interrupt handler function
* @flags: flags (see IRQF_* above)
* @name: name of the device
* @dev_id: cookie to identify the device
* @next: pointer to the next irqaction for shared interrupts
* @irq: interrupt number
* @dir: pointer to the proc/irq/NN/name entry
* @thread_fn: interupt handler function for threaded interrupts
* @thread: thread pointer for threaded interrupts
* @thread_flags: flags related to @thread
*/
struct irqaction {
irq_handler_t handler;
unsigned long flags;
const char *name;
void *dev_id;
struct irqaction *next;
int irq;
struct proc_dir_entry *dir;
irq_handler_t thread_fn;
struct task_struct *thread;
unsigned long thread_flags;
};
struct irq_2_iommu;
/**
* struct irq_desc - interrupt descriptor
* @irq: interrupt number for this descriptor
* @timer_rand_state: pointer to timer rand state struct
* @kstat_irqs: irq stats per cpu
* @irq_2_iommu: iommu with this irq
* @handle_irq: highlevel irq-events handler [if NULL, __do_IRQ()]
* @chip: low level interrupt hardware access
* @msi_desc: MSI descriptor
* @handler_data: per-IRQ data for the irq_chip methods
* @chip_data: platform-specific per-chip private data for the chip
* methods, to allow shared chip implementations
* @action: the irq action chain
* @status: status information
* @depth: disable-depth, for nested irq_disable() calls
* @wake_depth: enable depth, for multiple set_irq_wake() callers
* @irq_count: stats field to detect stalled irqs
* @last_unhandled: aging timer for unhandled count
* @irqs_unhandled: stats field for spurious unhandled interrupts
* @lock: locking for SMP
* @affinity: IRQ affinity on SMP
* @node: node index useful for balancing
* @pending_mask: pending rebalanced interrupts
* @threads_active: number of irqaction threads currently running
* @wait_for_threads: wait queue for sync_irq to wait for threaded handlers
* @dir: /proc/irq/ procfs entry
* @name: flow handler name for /proc/interrupts output
*/
中断描述符表
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;
struct irq_chip *chip;
struct msi_desc *msi_desc;
void *handler_data;
void *chip_data;
struct irqaction *action; /* IRQ action list */
unsigned int status; /* IRQ status */
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;
raw_spinlock_t lock;
#ifdef CONFIG_SMP
cpumask_var_t affinity;
const struct cpumask *affinity_hint;
unsigned int node;
#ifdef CONFIG_GENERIC_PENDING_IRQ
cpumask_var_t pending_mask;
#endif
#endif
atomic_t threads_active;
wait_queue_head_t wait_for_threads;
#ifdef CONFIG_PROC_FS
struct proc_dir_entry *dir;
#endif
const char *name;
} ____cacheline_internodealigned_in_smp;
中断向量号：
中断向量：Intel X86 的系列微机共支持256种向量中断，为使处理器可以容易地识别每种中断源，将他们从0到256进行了编号，即赋以一个中断类型码n，Intel把这个8位的无符号整数叫做向量，即中断向量。
所有256种中断可分为两大类：异常和中断。
异常又分为故障（fault）和陷阱（Trap），他们的共同特点是既不使用中断控制器，又不能被屏蔽。
中断又分为：外部可屏蔽中断和外部非屏蔽中断。所有I/O设备产生的中断均称引起可屏蔽中断，而紧急的事件（如硬件故障）引起的故障则产生非屏蔽中断。
非屏蔽中断的向量和异常的向量是固定的，而可屏蔽中断的向量可以通过对中断控制器的编程来改变
Linux对256个中断向量的分配如下：
编号0～31的向量对应于异常和非屏蔽中断（中断向量类型是固定的）
编号为32～47的向量（即由I/O设备引起的中断）分配给可屏蔽中断
剩余的、编号为48～255的向量用来标示软中断。Linux只使用了其中的一个（即128或0x80向量）来实现系统调用。
中断描述符表：
在实地址模式中，cpu把内存中从0开始的1KB空间作为一个中断向量表。表中的每个表项占四个字节，有两个字节的段地址和两个字节的偏移量组成，这样构成的地址便是相应中断处理程序的入口地址。但是，在保护 模式下，有4个字节的表项构成的中断向量表显然满足不了要求。这是因为：除了两个字节的段描述符，偏移量必须用4个字节来表示而且要有反应模式切换的信息。因此，在保护模式下，中断向量表中的表项由八个字节组成。中断向量表也该称作中断描述符表（Interrupt Descriptor Table，IDT），其中的每个表项叫做一个门描述符（gate descriptor）
中断控制器：
中断控制器是一种硬件结构，在Inter X86中使用中断控制器8259A来响应15个外部中断源每个8259A可以管理8个中断源。
中断线：
与中断源相连的每条线叫做中断线，常把申请一条中断线称为申请一个IRQ或者是申请一个中断号。
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