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| FreeBSD 5 内核源代码分析之中断处理 |
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FAKE_MCOUNT(13*4(%esp)) ; /* XXX late to avoid double count */ \ pushl $irq_num; /* pass the IRQ */ \ call atpic_handle_intr ; \ addl $4, %esp ; /* discard the parameter */ \ ; \ MEXITCOUNT ; \ jmp doreti |
IRQ产生时，系统根据产生中断的IRQ号找到相应的中断向量入口，即此处的IDT_VEC(vec_name)，
再这里，构造好函数atpic_handle_intr()的调用栈后，将转到atpic_handle_intr()进行处理。
同系统调用一样，这里的调用栈struct intrframe既是atpic_handle_intr()的参数，也是中断
返回时用以恢复现场的寄存器状态。
| 代码: |
/* Interrupt stack frame */ struct intrframe { int if_vec; int if_fs; int if_es; int if_ds; int if_edi; int if_esi; int if_ebp; int :32; int if_ebx; int if_edx; 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 %d\n", iframe.if_vec)); isrc = &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_ 上一页 [1] [2] [3] [4] [5] [6] [7] 下一页 |
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