Queue of events sorted in time order. More...

#include <eventq.hh>

Classes
class	ScopedMigration

class	ScopedRelease

Public Member Functions
	EventQueue (const std::string &n)

void	schedule (Event *event, Tick when, bool global=false)
	Schedule the given event on this queue. More...

void	deschedule (Event *event)
	Deschedule the specified event. More...

void	reschedule (Event *event, Tick when, bool always=false)
	Reschedule the specified event. More...

Tick	nextTick () const

void	setCurTick (Tick newVal)

Tick	getCurTick () const
	While curTick() is useful for any object assigned to this event queue, if an object that is assigned to another event queue (or a non-event object) need to access the current tick of this event queue, this function is used. More...

Event *	getHead () const

Event *	serviceOne ()

void	serviceEvents (Tick when)
	process all events up to the given timestamp. More...

bool	empty () const
	Returns true if no events are queued. More...

void	dump () const
	This is a debugging function which will print everything on the event queue. More...

bool	debugVerify () const

void	handleAsyncInsertions ()
	Function for moving events from the async_queue to the main queue. More...

virtual void	wakeup (Tick when=(Tick) -1)
	Function to signal that the event loop should be woken up because an event has been scheduled by an agent outside the gem5 event loop(s) whose event insertion may not have been noticed by gem5. More...

Event *	replaceHead (Event *s)
	function for replacing the head of the event queue, so that a different set of events can run without disturbing events that have already been scheduled. More...

void	checkpointReschedule (Event *event)
	Reschedule an event after a checkpoint. More...

virtual	~EventQueue ()


virtual const std::string	name () const

void	name (const std::string &st)


void	lock ()
	Provide an interface for locking/unlocking the event queue. More...

void	unlock ()

Private Member Functions
void	insert (Event *event)
	Insert / remove event from the queue. More...

void	remove (Event *event)

void	asyncInsert (Event *event)
	Function for adding events to the async queue. More...

	EventQueue (const EventQueue &)

Private Attributes
std::string	objName

Event *	head

Tick	_curTick

std::mutex	async_queue_mutex
	Mutex to protect async queue. More...

std::list< Event * >	async_queue
	List of events added by other threads to this event queue. More...

std::mutex	service_mutex
	Lock protecting event handling. More...

Detailed Description

Queue of events sorted in time order.

Events are scheduled (inserted into the event queue) using the schedule() method. This method either inserts a synchronous or asynchronous event.

Synchronous events are scheduled using schedule() method with the argument 'global' set to false (default). This should only be done from a thread holding the event queue lock (EventQueue::service_mutex). The lock is always held when an event handler is called, it can therefore always insert events into its own event queue unless it voluntarily releases the lock.

Events can be scheduled across thread (and event queue borders) by either scheduling asynchronous events or taking the target event queue's lock. However, the lock should never be taken directly since this is likely to cause deadlocks. Instead, code that needs to schedule events in other event queues should temporarily release its own queue and lock the new queue. This prevents deadlocks since a single thread never owns more than one event queue lock. This functionality is provided by the ScopedMigration helper class. Note that temporarily migrating between event queues can make the simulation non-deterministic, it should therefore be limited to cases where that can be tolerated (e.g., handling asynchronous IO or fast-forwarding in KVM).

Asynchronous events can also be scheduled using the normal schedule() method with the 'global' parameter set to true. Unlike the previous queue migration strategy, this strategy is fully deterministic. This causes the event to be inserted in a separate queue of asynchronous events (async_queue), which is merged main event queue at the end of each simulation quantum (by calling the handleAsyncInsertions() method). Note that this implies that such events must happen at least one simulation quantum into the future, otherwise they risk being scheduled in the past by handleAsyncInsertions().

Definition at line 617 of file eventq.hh.

Constructor & Destructor Documentation

◆ EventQueue()

EventQueue::EventQueue ( const EventQueue & )

private

◆ ~EventQueue()

virtual EventQueue::~EventQueue ( )

inlinevirtual

Definition at line 964 of file eventq.hh.

References deschedule(), empty(), and getHead().

Member Function Documentation

◆ asyncInsert()

void EventQueue::asyncInsert ( Event * event )

private

Function for adding events to the async queue.

The added events are added to main event queue later. Threads, other than the owning thread, should call this function instead of insert().

Definition at line 427 of file eventq.cc.

References async_queue, async_queue_mutex, and MipsISA::event.

Referenced by schedule().

◆ checkpointReschedule()

void EventQueue::checkpointReschedule ( Event * event )

Reschedule an event after a checkpoint.

Since events don't know which event queue they belong to, parent objects need to reschedule events themselves. This method conditionally schedules an event that has the Scheduled flag set. It should be called by parent objects after unserializing an object.

@warn Only use this method after unserializing an Event.

Definition at line 279 of file eventq.cc.

References MipsISA::event, and EventBase::Scheduled.

◆ debugVerify()

bool EventQueue::debugVerify ( ) const

Definition at line 313 of file eventq.cc.

References cprintf(), Event::dump(), Event::nextBin, Event::nextInBin, Event::priority(), and Event::when().

◆ getHead()

Event* EventQueue::getHead ( ) const

inline

Definition at line 851 of file eventq.hh.

References head.

Referenced by RubySystem::memWriteback(), and ~EventQueue().

◆ handleAsyncInsertions()

void EventQueue::handleAsyncInsertions ( )

Function for moving events from the async_queue to the main queue.

Definition at line 435 of file eventq.cc.

References async_queue, async_queue_mutex, curEventQueue(), and insert().

Referenced by doSimLoop(), and GlobalSyncEvent::BarrierEvent::process().

◆ insert()

void EventQueue::insert ( Event * event )

private

Insert / remove event from the queue.

Should only be called by thread operating this queue.

Definition at line 111 of file eventq.cc.

References MipsISA::event, Event::insertBefore(), and Event::nextBin.

Referenced by handleAsyncInsertions(), reschedule(), and schedule().

◆ lock()

void EventQueue::lock ( )

inline

Provide an interface for locking/unlocking the event queue.

@warn Do NOT use these methods directly unless you really know what you are doing. Incorrect use can easily lead to simulator deadlocks.

See also: EventQueue::ScopedMigration.; EventQueue::ScopedRelease; EventQueue

Definition at line 947 of file eventq.hh.

References service_mutex.

Referenced by DistIface::RecvScheduler::pushPacket(), DistIface::recvThreadFunc(), EventQueue::ScopedMigration::ScopedMigration(), EventQueue::ScopedMigration::~ScopedMigration(), and EventQueue::ScopedRelease::~ScopedRelease().

◆ nextTick()

Tick EventQueue::nextTick ( ) const

inline

Definition at line 836 of file eventq.hh.

References head, and Event::when().

Referenced by doSimLoop(), Iris::ThreadContext::maintainStepping(), serviceEvents(), and BaseKvmCPU::setupInstStop().

◆ remove()

void EventQueue::remove ( Event * event )

private

Definition at line 165 of file eventq.cc.

References MipsISA::event, Event::nextBin, panic, and Event::removeItem().

Referenced by deschedule(), and reschedule().

◆ replaceHead()

Event * EventQueue::replaceHead ( Event * s )

function for replacing the head of the event queue, so that a different set of events can run without disturbing events that have already been scheduled.

Already scheduled events can be processed by replacing the original head back. USING THIS FUNCTION CAN BE DANGEROUS TO THE HEALTH OF THE SIMULATOR. NOT RECOMMENDED FOR USE.

Definition at line 355 of file eventq.cc.

References ArmISA::s, and ArmISA::t.

Referenced by RubySystem::startup().

◆ serviceOne()

Event * EventQueue::serviceOne ( )

Definition at line 197 of file eventq.cc.

References Flags< T >::clear(), DTRACE, MipsISA::event, Event::flags, EventBase::IsMainQueue, X86ISA::lock, EventBase::Managed, Event::nextBin, Event::nextInBin, EventBase::Scheduled, and EventBase::Squashed.

Referenced by doSimLoop(), and serviceEvents().

◆ setCurTick()

void EventQueue::setCurTick ( Tick newVal )

inline

Definition at line 837 of file eventq.hh.

References _curTick.

Referenced by StatTest::run(), serviceEvents(), and EventManager::setCurTick().

◆ unlock()

void EventQueue::unlock ( )

inline

Definition at line 948 of file eventq.hh.

References service_mutex.

Referenced by DistIface::RecvScheduler::pushPacket(), DistIface::recvThreadFunc(), EventQueue::ScopedMigration::ScopedMigration(), EventQueue::ScopedRelease::ScopedRelease(), and EventQueue::ScopedMigration::~ScopedMigration().

Member Data Documentation

◆ _curTick

Tick EventQueue::_curTick

private

Definition at line 622 of file eventq.hh.

Referenced by getCurTick(), and setCurTick().

◆ async_queue

std::list<Event*> EventQueue::async_queue

private

List of events added by other threads to this event queue.

Definition at line 628 of file eventq.hh.

Referenced by asyncInsert(), and handleAsyncInsertions().

◆ async_queue_mutex

std::mutex EventQueue::async_queue_mutex

private

Mutex to protect async queue.

Definition at line 625 of file eventq.hh.

Referenced by asyncInsert(), and handleAsyncInsertions().

◆ head

Event* EventQueue::head

private

Definition at line 621 of file eventq.hh.

Referenced by empty(), getHead(), and nextTick().

◆ objName

std::string EventQueue::objName

private

Definition at line 620 of file eventq.hh.

Referenced by name().

◆ service_mutex

std::mutex EventQueue::service_mutex

private

Lock protecting event handling.

This lock is always taken when servicing events. It is assumed that the thread scheduling new events (not asynchronous events though) have taken this lock. This is normally done by serviceOne() since new events are typically scheduled as a response to an earlier event.

This lock is intended to be used to temporarily steal an event queue to support inter-thread communication when some deterministic timing can be sacrificed for speed. For example, the KVM CPU can use this support to access devices running in a different thread.

See also: EventQueue::ScopedMigration.; EventQueue::ScopedRelease; EventQueue::lock(); EventQueue::unlock()

Definition at line 650 of file eventq.hh.

Referenced by lock(), and unlock().

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

sim/eventq.hh
sim/eventq.cc

Classes

Public Member Functions

Private Member Functions

Private Attributes

Detailed Description

Constructor & Destructor Documentation

◆ EventQueue()

◆ ~EventQueue()

Member Function Documentation

◆ asyncInsert()

◆ checkpointReschedule()

◆ debugVerify()

◆ getHead()

◆ handleAsyncInsertions()

◆ insert()

◆ lock()

◆ nextTick()

◆ remove()

◆ replaceHead()

◆ serviceOne()

◆ setCurTick()

◆ unlock()

Member Data Documentation

◆ _curTick

◆ async_queue

◆ async_queue_mutex

◆ head

◆ objName

◆ service_mutex