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system.cc

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// system.cc 
//      Nachos initialization and cleanup routines.
//
// 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.

#include "copyright.h"
#include "system.h"

// This defines *all* of the global data structures used by Nachos.
// These are all initialized and de-allocated by this file.

Thread *currentThread;                  // the thread we are running now
Thread *threadToBeDestroyed;            // the thread that just finished
Scheduler *scheduler;                   // the ready list
Interrupt *interrupt;                   // interrupt status
Statistics *stats;                      // performance metrics
Timer *timer;                           // the hardware timer device,
                                        // for invoking context switches

#ifdef FILESYS_NEEDED
FileSystem  *fileSystem;
#endif

#ifdef FILESYS
SynchDisk   *synchDisk;
#endif

#ifdef USER_PROGRAM     // requires either FILESYS or FILESYS_STUB
Machine *machine;       // user program memory and registers
#endif

#ifdef NETWORK
PostOffice *postOffice;
#endif


// External definition, to allow us to take a pointer to this function
extern void Cleanup();


//----------------------------------------------------------------------
// TimerInterruptHandler
//      Interrupt handler for the timer device.  The timer device is
//      set up to interrupt the CPU periodically (once every TimerTicks).
//      This routine is called each time there is a timer interrupt,
//      with interrupts disabled.
//
//      Note that instead of calling Yield() directly (which would
//      suspend the interrupt handler, not the interrupted thread
//      which is what we wanted to context switch), we set a flag
//      so that once the interrupt handler is done, it will appear as 
//      if the interrupted thread called Yield at the point it is 
//      was interrupted.
//
//      "dummy" is because every interrupt handler takes one argument,
//              whether it needs it or not.
//----------------------------------------------------------------------
static void
TimerInterruptHandler(int dummy)
{
    if (interrupt->getStatus() != IdleMode)
        interrupt->YieldOnReturn();
}

//----------------------------------------------------------------------
// Initialize
//      Initialize Nachos global data structures.  Interpret command
//      line arguments in order to determine flags for the initialization.  
// 
//      "argc" is the number of command line arguments (including the name
//              of the command) -- ex: "nachos -d +" -> argc = 3 
//      "argv" is an array of strings, one for each command line argument
//              ex: "nachos -d +" -> argv = {"nachos", "-d", "+"}
//----------------------------------------------------------------------
void
Initialize(int argc, char **argv)
{
    int argCount;
    char* debugArgs = "";
    bool randomYield = FALSE;

#ifdef USER_PROGRAM
    bool debugUserProg = FALSE; // single step user program
#endif
#ifdef FILESYS_NEEDED
    bool format = FALSE;        // format disk
#endif
#ifdef NETWORK
    double rely = 1;            // network reliability
    int netname = 0;            // UNIX socket name
#endif
    
    for (argc--, argv++; argc > 0; argc -= argCount, argv += argCount) {
        argCount = 1;
        if (!strcmp(*argv, "-d")) {
            if (argc == 1)
                debugArgs = "+";        // turn on all debug flags
            else {
                debugArgs = *(argv + 1);
                argCount = 2;
            }
        } else if (!strcmp(*argv, "-rs")) {
            ASSERT(argc > 1);
            RandomInit(atoi(*(argv + 1)));      // initialize pseudo-random
                                                // number generator
            randomYield = TRUE;
            argCount = 2;
        }
#ifdef USER_PROGRAM
        if (!strcmp(*argv, "-s"))
            debugUserProg = TRUE;
#endif
#ifdef FILESYS_NEEDED
        if (!strcmp(*argv, "-f"))
            format = TRUE;
#endif
#ifdef NETWORK
        if (!strcmp(*argv, "-l")) {
            ASSERT(argc > 1);
            rely = atof(*(argv + 1));
            argCount = 2;
        } else if (!strcmp(*argv, "-m")) {
            ASSERT(argc > 1);
            netname = atoi(*(argv + 1));
            argCount = 2;
        }
#endif
    }

    DebugInit(debugArgs);                       // initialize DEBUG messages
    stats = new Statistics();                   // collect statistics
    interrupt = new Interrupt;                  // start up interrupt handling
    scheduler = new Scheduler();                // initialize the ready queue
    if (randomYield)                            // start the timer (if needed)
        timer = new Timer(TimerInterruptHandler, 0, randomYield);

    threadToBeDestroyed = NULL;

    // We didn't explicitly allocate the current thread we are running in.
    // But if it ever tries to give up the CPU, we better have a Thread
    // object to save its state. 
    currentThread = new Thread("main");         
    currentThread->setStatus(RUNNING);

    interrupt->Enable();
    CallOnUserAbort(Cleanup);                   // if user hits ctl-C
    
#ifdef USER_PROGRAM
    machine = new Machine(debugUserProg);       // this must come first
#endif

#ifdef FILESYS
    synchDisk = new SynchDisk("DISK");
#endif

#ifdef FILESYS_NEEDED
    fileSystem = new FileSystem(format);
#endif

#ifdef NETWORK
    postOffice = new PostOffice(netname, rely, 10);
#endif
}

//----------------------------------------------------------------------
// Cleanup
//      Nachos is halting.  De-allocate global data structures.
//----------------------------------------------------------------------
void
Cleanup()
{
    printf("\nCleaning up...\n");
#ifdef NETWORK
    delete postOffice;
#endif
    
#ifdef USER_PROGRAM
    delete machine;
#endif

#ifdef FILESYS_NEEDED
    delete fileSystem;
#endif

#ifdef FILESYS
    delete synchDisk;
#endif
    
    delete timer;
    delete scheduler;
    delete interrupt;
    
    Exit(0);
}

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