Initial version

code/machine/interrupt.h

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+// interrupt.h 
+//	Data structures to emulate low-level interrupt hardware.
+//
+//	The hardware provides a routine (SetLevel) to enable or disable
+//	interrupts.
+//
+//	In order to emulate the hardware, we need to keep track of all
+//	interrupts the hardware devices would cause, and when they
+//	are supposed to occur.  
+//
+//	This module also keeps track of simulated time.  Time advances
+//	only when the following occur: 
+//		interrupts are re-enabled
+//		a user instruction is executed
+//		there is nothing in the ready queue
+//
+//	As a result, unlike real hardware, interrupts (and thus time-slice 
+//	context switches) cannot occur anywhere in the code where interrupts
+//	are enabled, but rather only at those places in the code where 
+//	simulated time advances (so that it becomes time to invoke an
+//	interrupt in the hardware simulation).
+//
+//	NOTE: this means that incorrectly synchronized code may work
+//	fine on this hardware simulation (even with randomized time slices),
+//	but it wouldn't work on real hardware.  (Just because we can't
+//	always detect when your program would fail in real life, does not 
+//	mean it's ok to write incorrectly synchronized code!)
+//
+//  DO NOT CHANGE -- part of the machine emulation
+//
+// 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.
+
+#ifndef INTERRUPT_H
+#define INTERRUPT_H
+
+#include "copyright.h"
+#include "list.h"
+
+// Interrupts can be disabled (IntOff) or enabled (IntOn)
+enum IntStatus { IntOff, IntOn };
+
+// Nachos can be running kernel code (SystemMode), user code (UserMode),
+// or there can be no runnable thread, because the ready list 
+// is empty (IdleMode).
+enum MachineStatus {IdleMode, SystemMode, UserMode};
+
+// IntType records which hardware device generated an interrupt.
+// In Nachos, we support a hardware timer device, a disk, a console
+// display and keyboard, and a network.
+enum IntType { TimerInt, DiskInt, ConsoleWriteInt, ConsoleReadInt, 
+				NetworkSendInt, NetworkRecvInt};
+
+// The following class defines an interrupt that is scheduled
+// to occur in the future.  The internal data structures are
+// left public to make it simpler to manipulate.
+
+class PendingInterrupt {
+  public:
+    PendingInterrupt(VoidFunctionPtr func, void *param,
+		     long long time, IntType kind);
+				// initialize an interrupt that will
+				// occur in the future
+
+    VoidFunctionPtr handler;    // The function (in the hardware device
+				// emulator) to call when the interrupt occurs
+    void *arg;                  // The argument to the function.
+    long long when;		// When the interrupt is supposed to fire
+    IntType type;		// for debugging
+};
+
+// The following class defines the data structures for the simulation
+// of hardware interrupts.  We record whether interrupts are enabled
+// or disabled, and any hardware interrupts that are scheduled to occur
+// in the future.
+
+class Interrupt:public dontcopythis {
+  public:
+    Interrupt();			// initialize the interrupt simulation
+    ~Interrupt();			// de-allocate data structures
+    
+    IntStatus SetLevel(IntStatus level);// Disable or enable interrupts 
+					// and return previous setting.
+
+    void Enable();			// Enable interrupts.
+    IntStatus getLevel() {return level;}// Return whether interrupts
+					// are enabled or disabled
+    
+    void Idle(); 			// The ready queue is empty, roll 
+					// simulated time forward until the 
+					// next interrupt
+
+    void Powerdown(); 			// quit and print out stats
+    
+    void YieldOnReturn();		// cause a context switch on return 
+					// from an interrupt handler
+
+    MachineStatus getStatus() { return status; } // idle, kernel, user
+    void setStatus(MachineStatus st) { status = st; }
+
+    void DumpState();			// Print interrupt state
+
+
+    // NOTE: the following are internal to the hardware simulation code.
+    // DO NOT call these directly.  I should make them "private",
+    // but they need to be public since they are called by the
+    // hardware device simulators.
+
+    void Schedule(VoidFunctionPtr handler,// Schedule an interrupt to occur
+	void *arg, long long when, IntType type);// at time ``when''.  This is called
+    					// by the hardware device simulators.
+    
+    void OneTick();       		// Advance simulated time
+
+  private:
+    IntStatus level;		// are interrupts enabled or disabled?
+    List *pending;		// the list of interrupts scheduled
+				// to occur in the future
+    bool inHandler;		// TRUE if we are running an interrupt handler
+    bool yieldOnReturn; 	// TRUE if we are to context switch
+				// on return from the interrupt handler
+    MachineStatus status;	// idle, kernel mode, user mode
+
+    // these functions are internal to the interrupt simulation code
+
+    bool CheckIfDue(bool advanceClock); // Check if an interrupt is supposed
+					// to occur now
+
+    void ChangeLevel(IntStatus old, 	// SetLevel, without advancing the
+	IntStatus now);  		// simulated time
+};
+
+#endif // INTERRRUPT_H