nachos.threads
Class Alarm

java.lang.Object
  nachos.threads.Alarm

public class Alarm
extends Object

Uses the hardware timer to provide preemption, and to allow threads to sleep until a certain time.

Constructor Summary

Alarm()
Allocate a new Alarm.

Method Summary

void	timerInterrupt() The timer interrupt handler.
void	waitUntil(long x) Put the current thread to sleep for at least x ticks, waking it up in the timer interrupt handler.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Alarm

public Alarm()

Allocate a new Alarm. Set the machine's timer interrupt handler to this alarm's callback.

Note: Nachos will not function correctly with more than one alarm.

Method Detail

timerInterrupt

public void timerInterrupt()

The timer interrupt handler. This is called by the machine's timer periodically (approximately every 500 clock ticks). Causes the current thread to yield, forcing a context switch if there is another thread that should be run.

waitUntil

public void waitUntil(long x)

Put the current thread to sleep for at least x ticks, waking it up in the timer interrupt handler. The thread must be woken up (placed in the scheduler ready set) during the first timer interrupt where

(current time) >= (WaitUntil called time)+(x)

Parameters:

x - the minimum number of clock ticks to wait.

See Also:

Timer.getTime()