Scheduler Class Reference

The scheduler plans the threads' execution order and, from this, selects the next thread to be running. More...

#include <thread/scheduler.h>

Inheritance diagram for Scheduler:

Collaboration diagram for Scheduler:

Static Public Member Functions
static void	schedule ()
	Start scheduling. More...
static void	ready (Thread *that)
	Include a thread in scheduling decisions. More...
static void	exit ()
	(Self-)termination of the calling thread. More...
static void	kill (Thread *that)
	Kills the passed thread. More...
static void	resume ()
	Issue a thread change. More...
static bool	isEmpty ()
	Checks whether the ready queue is empty. More...
static void	block (Waitingroom *waitingroom)
	Blocks the calling thread in and enqueues the thread in the provided waitingroom. More...
static void	wakeup (Thread *customer)
	Wake up a sleeping thread. More...
Static Public Member Functions inherited from Dispatcher
static Thread *	active ()
	Returns the thread currently running on the CPU core calling this method.
static bool	isActive (const Thread *thread, unsigned *cpu=nullptr)
	Check if thread is currently active. More...
static void	go (Thread *first)
	This method stores first as life pointer for this CPU core and triggers the execution of first thread. More...
static void	dispatch (Thread *next)
	Updates the life pointer to next and issues a thread change from the old to the new life pointer. More...

Detailed Description

The scheduler plans the threads' execution order and, from this, selects the next thread to be running.

The scheduler manages the ready queue (a private Queue object), that is the list of threads that are ready to execute. The scheduler arranges threads in a FIFO order, that is, when a thread is set ready, it will be appended to the end of the queue, while threads to be executed are taken from the front of the queue.

Member Function Documentation

schedule()

void Scheduler::schedule ( )

static

Start scheduling.

This method starts the scheduling by removing the first thread from the ready queue and activating it. MPStuBS needs to call this method once for every CPU core to dispatch the first thread.

ready()

void Scheduler::ready ( Thread *  that )

static

Include a thread in scheduling decisions.

This method will register a thread for scheduling. It will be appended to the ready queue and dispatched once its time has come.

Parameters

that	Thread to be scheduled

exit()

void Scheduler::exit ( )

static

(Self-)termination of the calling thread.

This method can be used by a thread to exit itself. The calling thread will not be appended to the ready queue; a reschedule will be issued.

kill()

void Scheduler::kill ( Thread *  that )

static

Kills the passed thread.

This method is used to kill the Thread that. For OOStuBS, it is sufficient to remove that from the ready queue and, thereby, exclude the thread from scheduling. For MPStuBS, a simple removal is not sufficient, as the thread might currently be running on another CPU core. In this case, the thread needs to be marked as dying (a flag checked by resume prior to enqueuing into the ready queue) and the executing CPU core needs to be notified.

Note

The thread should be able to kill itself.

resume()

void Scheduler::resume ( )

static

Issue a thread change.

This method issues the change of the currently active thread without requiring the calling thread to be aware of the other threads. Scheduling decisions, i.e. which thread will be run next, are made by the scheduler itself with the knowledge of the currently ready threads. The currently active thread is appended to the end of the queue; the first thread in the queue will be activated (to implement the FIFO policy).

isEmpty()

static bool Scheduler::isEmpty ( )

inlinestatic

Checks whether the ready queue is empty.

Todo:

Implement Method

block()

void Scheduler::block ( Waitingroom *  waitingroom )

static

Blocks the calling thread in and enqueues the thread in the provided waitingroom.

Calling this method will issue a reschedule and, resultingly, pass the processor to the next thread from the ready queue. The calling thread will be waiting in the provided waitingroom.

Todo:

Implement Method

wakeup()

void Scheduler::wakeup ( Thread *  customer )

static

Wake up a sleeping thread.

Waking up a thread means inserting the thread into the ready queue and removing it from the event it might be waiting for.

Parameters

customer

Sleeping thread to be woken up.

Todo:

Implement Method

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The documentation for this class was generated from the following files:

• thread/scheduler.h
• thread/scheduler.cc