kernel(一) interrupts

the keyboard controller(the hardware device) =======================> processor=============>operating system

                                                                          an electrical signal                                        signal

 

Different devices can be associated with different interrupts by means of a unique value associated with each interrupt.

the unique value called interrupt request lines( IRQ ). for example, on the classic PC, IRQ zero is the timer interrupt 

and IRQ one is the keyword interrupt.

 

Exceptions:

                exceptions occur synchronously with respect to the processor clock, indeed, they are often called synchronous 

interrupts.Exceptions are produced by the processor while executing instructions either in respon to a programming error.

 

Interrupt Handlers

               The function the kernel runs in response to a specific interrupt is called an interrupt handler or interrupt service routine(ISR).

the interrupt handlers run  in a special context called interrupt context.

 

 

Interrupt Context

                           interrupt context is time-critical because the interrupt handler interrupts other code. it can't sleep. so this limits the 

functions that one can call from an interrupt handler.