void InterruptHandler::dispatch_interrupt(REGS * _r) {
/* -- INTERRUPT NUMBER */
unsigned int int_no = _r->int_no - IRQ_BASE;
//Console::puts("INTERRUPT DISPATCHER: int_no = ");
////Console::putui(int_no);
////Console::puts("\n");
assert((int_no >= 0) && (int_no < IRQ_TABLE_SIZE));
/* -- HAS A HANDLER BEEN REGISTERED FOR THIS INTERRUPT NO? */
InterruptHandler * handler = handler_table[int_no];
/* This is an interrupt that was raised by the interrupt controller. We need
to send and end-of-interrupt (EOI) signal to the controller after the
interrupt has been handled. */
// When the timer ticks 20ms, an interrupt happens.
// Then the interrupt handler will take care of this interrupt and do the following.
// In dispatch_interrupt function, it looks at the handler table, finds the right handler, and
// then calls the corresponding handler function.
// However, this function will not be returned in a short time.
// If the new thread does not pend from here, it will return from somewhere else and therefore the
// EOI signal will not be sent to PIC soon. Also, if this is the case, when this thread regains
// CPU later, it will return from here, causing an unreansonable EOI signal sent.
// To avoid this case, we must send EOI signal before the handler function (context switch) is called.
/* Check if the interrupt was generated by the slave interrupt controller.
If so, send an End-of-Interrupt (EOI) message to the slave controller. */
if (generated_by_slave_PIC(int_no)) {
outportb(0xA0, 0x20);
}
/* Send an EOI message to the master interrupt controller. */
outportb(0x20, 0x20);
//Then we call the corresponding handler function
if (!handler) {
/* --- NO DEFAULT HANDLER HAS BEEN REGISTERED. SIMPLY RETURN AN ERROR. */
Console::puts("INTERRUPT NO: ");
Console::puti(int_no);
Console::puts("\n");
Console::puts("NO DEFAULT INTERRUPT HANDLER REGISTERED\n");
//abort();
}
else {
/* -- HANDLE THE INTERRUPT */
handler->handle_interrupt(_r);
}
}
void InterruptHandler::dispatch_interrupt(REGS * _r) {
/* -- INTERRUPT NUMBER */
unsigned int int_no = _r->int_no - IRQ_BASE;
//Console::puts("INTERRUPT DISPATCHER: int_no = ");
//Console::putui(int_no);
//Console::puts("\n");
assert((int_no >= 0) && (int_no < IRQ_TABLE_SIZE));
/* -- HAS A HANDLER BEEN REGISTERED FOR THIS INTERRUPT NO? */
InterruptHandler * handler = handler_table[int_no];
if (!handler) {
/* --- NO DEFAULT HANDLER HAS BEEN REGISTERED. SIMPLY RETURN AN ERROR. */
Console::puts("INTERRUPT NO: ");
Console::puti(int_no);
Console::puts("\n");
Console::puts("NO DEFAULT INTERRUPT HANDLER REGISTERED\n");
// abort();
}
else {
/* -- HANDLE THE INTERRUPT */
/* This is an interrupt that was raised by the interrupt controller. We need
to send and end-of-interrupt (EOI) signal to the controller after the
interrupt has been handled. */
/* Check if the interrupt was generated by the slave interrupt controller.
If so, send an End-of-Interrupt (EOI) message to the slave controller. */
if (generated_by_slave_PIC(int_no)) {//modified to inform the control the interupt is being handled before the call to the handler
outportb(0xA0, 0x20);//this will allow context switch during handler
}
/* Send an EOI message to the master interrupt controller. */
outportb(0x20, 0x20);
// we send interupt has been handled before calling handle interupt to prevent the interupt from not being acknoledged
//when a context switch occurs inside of the handler
// and when the calling thread finally returns from the context switch to not send the interupt handled message
//because at this point it has already been handled and if the PIC is waiting for a handled message it is a different interupt
handler->handle_interrupt(_r);
//dont do anything after handler to prevent interupts not being handled
}
}
void InterruptHandler::dispatch_interrupt(REGS * _r) {
/* -- INTERRUPT NUMBER */
unsigned int int_no = _r->int_no - IRQ_BASE;
//Console::puts("INTERRUPT DISPATCHER: int_no = ");
//Console::putui(int_no);
//Console::puts("\n");
assert((int_no >= 0) && (int_no < IRQ_TABLE_SIZE));
/* -- HAS A HANDLER BEEN REGISTERED FOR THIS INTERRUPT NO? */
InterruptHandler * handler = handler_table[int_no];
if (!handler) {
/* --- NO DEFAULT HANDLER HAS BEEN REGISTERED. SIMPLY RETURN AN ERROR. */
Console::puts("INTERRUPT NO: ");
Console::puti(int_no);
Console::puts("\n");
Console::puts("NO DEFAULT INTERRUPT HANDLER REGISTERED\n");
// abort();
}
else {
/* -- HANDLE THE INTERRUPT */
/* Signal PIC that the interrupt has been handled and then make the call to handle interrupt */
if(int_no == 0)
outportb(0x20, 0x20);
handler->handle_interrupt(_r);
}
/* This is an interrupt that was raised by the interrupt controller. We need
to send and end-of-interrupt (EOI) signal to the controller after the
interrupt has been handled. */
/* Check if the interrupt was generated by the slave interrupt controller.
If so, send an End-of-Interrupt (EOI) message to the slave controller. */
if (generated_by_slave_PIC(int_no)) {
outportb(0xA0, 0x20);
}
/* Add additional check to see that we don't send EOI for interrupt 0, since its already done*/
/* Send an EOI message to the master interrupt controller. */
outportb(0x20, 0x20);
}
