中断产生流程
中断向量表
entry.S (arch\arm64\kernel)
ENTRY(vectors)
kernel_ventry 1, sync_invalid // Synchronous EL1t
kernel_ventry 1, irq_invalid // IRQ EL1t
kernel_ventry 1, fiq_invalid // FIQ EL1t
kernel_ventry 1, error_invalid // Error EL1t
kernel_ventry 1, sync // Synchronous EL1h
kernel_ventry 1, irq // IRQ EL1h
kernel_ventry 1, fiq_invalid // FIQ EL1h
kernel_ventry 1, error_invalid // Error EL1h
kernel_ventry 0, sync // Synchronous 64-bit EL0
kernel_ventry 0, irq // IRQ 64-bit EL0
kernel_ventry 0, fiq_invalid // FIQ 64-bit EL0
kernel_ventry 0, error_invalid // Error 64-bit EL0
#ifdef CONFIG_COMPAT
kernel_ventry 0, sync_compat, 32 // Synchronous 32-bit EL0
kernel_ventry 0, irq_compat, 32 // IRQ 32-bit EL0
kernel_ventry 0, fiq_invalid_compat, 32 // FIQ 32-bit EL0
kernel_ventry 0, error_invalid_compat, 32 // Error 32-bit EL0
#else
kernel_ventry 0, sync_invalid, 32 // Synchronous 32-bit EL0
kernel_ventry 0, irq_invalid, 32 // IRQ 32-bit EL0
kernel_ventry 0, fiq_invalid, 32 // FIQ 32-bit EL0
kernel_ventry 0, error_invalid, 32 // Error 32-bit EL0
#endif
END(vectors)
以el1_irq为例
el1_irq:
kernel_entry 1
enable_dbg
#ifdef CONFIG_TRACE_IRQFLAGS
bl trace_hardirqs_off
#endif
irq_handler
#ifdef CONFIG_PREEMPT
ldr w24, [tsk, #TSK_TI_PREEMPT] // get preempt count
cbnz w24, 1f // preempt count != 0
ldr x0, [tsk, #TSK_TI_FLAGS] // get flags
tbz x0, #TIF_NEED_RESCHED, 1f // needs rescheduling?
bl el1_preempt
1:
#endif
#ifdef CONFIG_TRACE_IRQFLAGS
bl trace_hardirqs_on
#endif
kernel_exit 1
ENDPROC(el1_irq)
从上kernel_entry 保存现场， irq_handler是中断处理函数，kernel_exit是恢复现场
中间CONFIG_PREEMPT宏包含一段抢占调度的代码，下面介绍一下irq_handler函数
.macro irq_handler
ldr_l x1, handle_arch_irq
mov x0, sp
irq_stack_entry //栈指针切换,切换到中断栈空间
blr x1 //跳到handle_arch_irq函数执行
irq_stack_exit //栈指针切换,退出中断栈空间
.endm
handle_arch_irq是通过set_handle_irq赋值的
路径：entry.S (kernel4.14\arch\arm64\kernel)
void __init set_handle_irq(void (*handle_irq)(struct pt_regs *))
{
if (handle_arch_irq)
return;
handle_arch_irq = handle_irq;
}
此set_handle_irq函数是在gic_init_bases函数中调用的 set_handle_irq(gic_handle_irq);
gic_handle_irq函数路径：Irq-gic-v3.c (kernel4.14\drivers\irqchip)
static asmlinkage void __exception_irq_entry gic_handle_irq(struct pt_regs *regs)
{
u32 irqnr;
do {
irqnr = gic_read_iar();//读取硬件中断号
if (likely(irqnr > 15 && irqnr < 1020) || irqnr >= 8192) {
int err;
if (static_key_true(&supports_deactivate))
gic_write_eoir(irqnr);
else
isb();
err = handle_domain_irq(gic_data.domain, irqnr, regs);
if (err) {
WARN_ONCE(true, "Unexpected interrupt received!\n");
if (static_key_true(&supports_deactivate)) {
if (irqnr < 8192)
gic_write_dir(irqnr);
} else {
gic_write_eoir(irqnr);
}
}
continue;
}
if (irqnr < 16) {//主要用于核间通信的中断
gic_write_eoir(irqnr);
if (static_key_true(&supports_deactivate))
gic_write_dir(irqnr);
#ifdef CONFIG_SMP
/*
* Unlike GICv2, we don't need an smp_rmb() here.
* The control dependency from gic_read_iar to
* the ISB in gic_write_eoir is enough to ensure
* that any shared data read by handle_IPI will
* be read after the ACK.
*/
handle_IPI(irqnr, regs);
#else
WARN_ONCE(true, "Unexpected SGI received!\n");
#endif
continue;
}
} while (irqnr != ICC_IAR1_EL1_SPURIOUS);
}
static inline int handle_domain_irq(struct irq_domain *domain,
unsigned int hwirq, struct pt_regs *regs)
{
return __handle_domain_irq(domain, hwirq, true, regs);
}
int __handle_domain_irq(struct irq_domain *domain, unsigned int hwirq,
bool lookup, struct pt_regs *regs)
{
struct pt_regs *old_regs = set_irq_regs(regs);
unsigned int irq = hwirq;
int ret = 0;
irq_enter();//进入中断上下文
#ifdef CONFIG_IRQ_DOMAIN
if (lookup)
irq = irq_find_mapping(domain, hwirq);//根据硬件中断号找到对应的软件中断号
#endif
/*
* Some hardware gives randomly wrong interrupts. Rather
* than crashing, do something sensible.
*/
if (unlikely(!irq || irq >= nr_irqs)) {
ack_bad_irq(irq);
ret = -EINVAL;
} else {
generic_handle_irq(irq);//进入一个中断的处理函数
}
irq_exit();//退出中断上下文
set_irq_regs(old_regs);
return ret;
}‘
generic_handle_irq函数如下：
int generic_handle_irq(unsigned int irq)
{
struct irq_desc *desc = irq_to_desc(irq);
if (!desc)
return -EINVAL;
generic_handle_irq_desc(desc);
return 0;
}
static inline void generic_handle_irq_desc(struct irq_desc *desc)
{
desc->handle_irq(desc);
}
desc->handle_irq通过gic_irq_domain_map初始化的，根据不同的中断号走不同的路径
gic_irq_domain_map’如下：
static int gic_irq_domain_map(struct irq_domain *d, unsigned int irq,
irq_hw_number_t hw)
{
struct irq_chip *chip = &gic_chip;
if (static_key_true(&supports_deactivate))
chip = &gic_eoimode1_chip;
/* SGIs are private to the core kernel */
if (hw < 16)
return -EPERM;
/* Nothing here */
if (hw >= gic_data.irq_nr && hw < 8192)
return -EPERM;
/* Off limits */
if (hw >= GIC_ID_NR)
return -EPERM;
/* PPIs *///PPI（Private Peripheral Interrupts）是指专用私有中断,通常用于CPU本地时钟等应用场景
if (hw < 32) {
irq_set_percpu_devid(irq);
irq_domain_set_info(d, irq, hw, chip, d->host_data,
handle_percpu_devid_irq, NULL, NULL);
irq_set_status_flags(irq, IRQ_NOAUTOEN);
}
/* SPIs */ //共享中断源允许多个处理器共享同一个中断源。SPI 中断主要用于处理外部设备引发的中断事件，如网络接口卡、硬盘控制器、串口控制器等外设的中断。
if (hw >= 32 && hw < gic_data.irq_nr) {
irq_domain_set_info(d, irq, hw, chip, d->host_data,
handle_fasteoi_irq, NULL, NULL);
irq_set_probe(irq);
}
/* LPIs *///特定于位置的外设中断(lpi)总是基于消息的，可以来自外设，也可以来自PCle根复核。
if (hw >= 8192 && hw < GIC_ID_NR) {
if (!gic_dist_supports_lpis())
return -EPERM;
irq_domain_set_info(d, irq, hw, chip, d->host_data,
handle_fasteoi_irq, NULL, NULL);
}
return 0;
}
通过gic_irq_domain_map函数可以看出desc->handle_irq(desc);是handle_percpu_devid_irq和handle_fasteoi_irq二选一
handle_percpu_devid_irq如下：
void handle_percpu_devid_irq(struct irq_desc *desc)
{
struct irq_chip *chip = irq_desc_get_chip(desc);
struct irqaction *action = desc->action;
unsigned int irq = irq_desc_get_irq(desc);
irqreturn_t res;
/*
* PER CPU interrupts are not serialized. Do not touch
* desc->tot_count.
*/
__kstat_incr_irqs_this_cpu(desc);
if (chip->irq_ack)
chip->irq_ack(&desc->irq_data);
if (likely(action)) {
trace_irq_handler_entry(irq, action);
res = action->handler(irq, raw_cpu_ptr(action->percpu_dev_id));//此处调用的就是注册中断时传递的中断处理函数
trace_irq_handler_exit(irq, action, res);
} else {
unsigned int cpu = smp_processor_id();
bool enabled = cpumask_test_cpu(cpu, desc->percpu_enabled);
if (enabled)
irq_percpu_disable(desc, cpu);
pr_err_once("Spurious%s percpu IRQ%u on CPU%u\n",
enabled ? " and unmasked" : "", irq, cpu);
}
if (chip->irq_eoi)
chip->irq_eoi(&desc->irq_data);
}
handle_fasteoi_irq如下：
void handle_fasteoi_irq(struct irq_desc *desc)
{
struct irq_chip *chip = desc->irq_data.chip;
raw_spin_lock(&desc->lock);
if (!irq_may_run(desc))
goto out;
desc->istate &= ~(IRQS_REPLAY | IRQS_WAITING);
/*
* If its disabled or no action available
* then mask it and get out of here:
*/
if (unlikely(!desc->action || irqd_irq_disabled(&desc->irq_data))) {
desc->istate |= IRQS_PENDING;
mask_irq(desc);
goto out;
}
kstat_incr_irqs_this_cpu(desc);
if (desc->istate & IRQS_ONESHOT)
mask_irq(desc);
preflow_handler(desc);
handle_irq_event(desc);
cond_unmask_eoi_irq(desc, chip);
raw_spin_unlock(&desc->lock);
return;
out:
if (!(chip->flags & IRQCHIP_EOI_IF_HANDLED))
chip->irq_eoi(&desc->irq_data);
raw_spin_unlock(&desc->lock);
}
irqreturn_t handle_irq_event(struct irq_desc *desc)
{
irqreturn_t ret;
desc->istate &= ~IRQS_PENDING;
irqd_set(&desc->irq_data, IRQD_IRQ_INPROGRESS);//设置中断状态
raw_spin_unlock(&desc->lock);
ret = handle_irq_event_percpu(desc);
raw_spin_lock(&desc->lock);
irqd_clear(&desc->irq_data, IRQD_IRQ_INPROGRESS);//清除中断状态
return ret;
}
irqreturn_t handle_irq_event_percpu(struct irq_desc *desc)
{
irqreturn_t retval;
unsigned int flags = 0;
retval = __handle_irq_event_percpu(desc, &flags);
add_interrupt_randomness(desc->irq_data.irq, flags);
if (!noirqdebug)
note_interrupt(desc, retval);
return retval;
}
irqreturn_t __handle_irq_event_percpu(struct irq_desc *desc, unsigned int *flags)
{
irqreturn_t retval = IRQ_NONE;
unsigned int irq = desc->irq_data.irq;
struct irqaction *action;
for_each_action_of_desc(desc, action) {//处理中断描述中的每一个action
irqreturn_t res;
trace_irq_handler_entry(irq, action);
res = action->handler(irq, action->dev_id);//此处调用的就是注册中断时传递的中断处理函数
trace_irq_handler_exit(irq, action, res);
if (WARN_ONCE(!irqs_disabled(),"irq %u handler %pF enabled interrupts\n",
irq, action->handler))
local_irq_disable();
switch (res) {
case IRQ_WAKE_THREAD:
/*
* Catch drivers which return WAKE_THREAD but
* did not set up a thread function
*/
if (unlikely(!action->thread_fn)) {
warn_no_thread(irq, action);
break;
}
__irq_wake_thread(desc, action);//此处中断线程化唤醒线程
/* Fall through to add to randomness */
case IRQ_HANDLED:
*flags |= action->flags;
break;
default:
break;
}
retval |= res;
}
return retval;
}
handle_IPI后续再写。
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