thread.h File Reference

Data structures for managing threads. More...

#include "copyright.h"
#include "utility.h"
#include "synch.h"

Go to the source code of this file.

Classes
class	Thread
	The following class defines a "thread control block" – which represents a single thread of execution. More...

Macros
#define	MachineStateSize   18
	CPU register state to be saved on context switch. The SPARC and MIPS only need 10 registers, but the Snake needs 18. For simplicity, this is just the max over all architectures.
#define	StackSize   (4 * 1024)
	Size of the thread's private execution stack. WATCH OUT IF THIS ISN'T BIG ENOUGH!!!!!

Enumerations
enum	ThreadStatus { JUST_CREATED, RUNNING, READY, BLOCKED }
	Thread state.

Functions
void	ThreadPrint (int arg)
	external function, dummy routine whose sole job is to call Thread::Print More...
void	ThreadRoot ()
void	SWITCH (Thread *oldThread, Thread *newThread)

Detailed Description

Data structures for managing threads.

Author

Olivier Hureau, Hugo Feydel , Julien ALaimo Data structures for managing threads. A thread represents sequential execution of code within a program. So the state of a thread includes the program counter, the processor registers, and the execution stack.

Note that because we allocate a fixed size stack for each thread, it is possible to overflow the stack – for instance, by recursing to too deep a level. The most common reason for this occuring is allocating large data structures on the stack. For instance, this will cause problems:

    void foo() { int buf[1000]; ...}

Instead, you should allocate all data structures dynamically:

    void foo() { int *buf = new int[1000]; ...}

Bad things happen if you overflow the stack, and in the worst case, the problem may not be caught explicitly. Instead, the only symptom may be bizarre segmentation faults. (Of course, other problems can cause seg faults, so that isn't a sure sign that your thread stacks are too small.)

One thing to try if you find yourself with seg faults is to increase the size of thread stack – ThreadStackSize.

In this interface, forking a thread takes two steps. We must first allocate a data structure for it: "t = new Thread". Only then can we do the fork: "t->fork(f, arg)".

Copyright (c) 1992-1993 The Regents of the University of California. All rights reserved. See copyright.h for copyright notice and limitation of liability and disclaimer of warranty provisions.

Function Documentation

void ThreadPrint

(

int

arg

)

external function, dummy routine whose sole job is to call Thread::Print

external function, dummy routine whose sole job is to call Thread::Print