FreeBSD 5 内核源代码分析之中断处理( 五 ) _云知道

int if_ecx;
int if_eax;
int :32; /* for compat with trap frame - trapno */
int :32; /* for compat with trap frame - err */
/* below portion defined in 386 hardware */
int if_eip;
int if_cs;
int if_eflags;
/* below only when crossing rings (e.g. user to kernel) */
int if_esp;
int if_ss;
};

void
atpic_handle_intr(struct intrframe iframe)
{
struct intsrc *isrc;

KASSERT((uint)iframe.if_vec < ICU_LEN,
("unknown int %dn", iframe.if_vec));
isrc = https://www.rkxy.com.cn/dnjc/&atintrs[iframe.if_vec].at_intsrc;

/*
* If we don"t have an ithread, see if this is a spurious
* interrupt.
*/
if (isrc->is_ithread == NULL &&
(iframe.if_vec == 7 || iframe.if_vec == 15)) {
int port, isr;

/*
* Read the ISR register to see if IRQ 7/15 is really
* pending. Reset read register back to IRR when done.
*/
port = ((struct atpic *)isrc->is_pic)->at_ioaddr;
mtx_lock_spin(&icu_lock);
outb(port, OCW3_SEL | OCW3_RR | OCW3_RIS);
isr = inb(port);
outb(port, OCW3_SEL | OCW3_RR);
mtx_unlock_spin(&icu_lock);
if ((isr & IRQ7) == 0)
return;
}
intr_execute_handlers(isrc, &iframe);
}

经过简单的有关8259A特有的检查，atpic_handle_intr()就转到intr_execute_handlers()
继续处理。

intr_execute_handlers()是一个重要的函数，它先得到IRQ号，然后判断是否是快速中断，
如果是，则直接在当前线程的上下文中运行，如果不是，则调度对应的中断线程来运行。
这个处理是被critical_enter()/critical_exit()保护起来的，以保证不会嵌套调度中断线程。
代码:
void
intr_execute_handlers(struct intsrc *isrc, struct intrframe *iframe)
{
struct thread *td;
struct ithd *it;
struct intrhand *ih;
int error, vector;

td = curthread;
td->td_intr_nesting_level;

/*
* We count software interrupts when we process them. The
* code here follows previous practice, but there"s an
* argument for counting hardware interrupts when they"re
* processed too.
*/
atomic_add_long(isrc->is_count, 1);
atomic_add_int(&cnt.v_intr, 1);

it = isrc->is_ithread;
if (it == NULL)
ih = NULL;
else
ih = TAILQ_FIRST(&it->it_handlers);

/*
* XXX: We assume that IRQ 0 is only used for the ISA timer
* device (clk).
*/
vector = isrc->is_pic->pic_vector(isrc);
if (vector == 0)
clkintr_pending = 1;

critical_enter();
if (ih != NULL && ih->ih_flags & IH_FAST) {
/*
* Execute fast interrupt handlers directly.
* To support clock handlers, if a handler registers
* with a NULL argument, then we pass it a pointer to
* a trapframe as its argument.
*/
TAILQ_FOREACH(ih, &it->it_handlers, ih_next) {
MPASS(ih->ih_flags & IH_FAST);
CTR3(KTR_INTR, "%s: executing handler %p(%p)",
__func__, ih->ih_handler,
ih->ih_argument == NULL ? iframe :
ih->ih_argument);
if (ih->ih_argument == NULL)
ih->ih_handler(iframe);
else
ih->ih_handler(ih->ih_argument);
}
isrc->is_pic->pic_eoi_source(isrc);
error = 0;

凡是总是有例外，fast中断不在中断线程的上下文中运行，而是直接在用户进程的上下文中运行
代码:
} else {
/*
* For stray and threaded interrupts, we mask and EOI the
* source.
*/
isrc->is_pic->pic_disable_source(isrc);
isrc->is_pic->pic_eoi_source(isrc);
if (ih == NULL)
error = EINVAL;
else
error = ithread_schedule(it, !cold);
}

其他的非快速中断则需要调度。这里先应答中断控制器，然后调度。
代码:
critical_exit();
if (error == EINVAL) {
atomic_add_long(isrc->is_straycount, 1);
if (*isrc->is_straycount < MAX_STRAY_LOG)
log(LOG_ERR, "stray irq%dn", vector);
else if (*isrc->is_straycount == MAX_STRAY_LOG)
log(LOG_CRIT,
"too many stray irq %d"s: not logging anymoren",
vector);

FreeBSD 5 内核源代码分析之中断处理( 五 )

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