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/*
* Copyright (c) 2000-2005 The Regents of The University of Michigan
* Copyright (c) 2013 Advanced Micro Devices, Inc.
* Copyright (c) 2013 Mark D. Hill and David A. Wood
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met: redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer;
* redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution;
* neither the name of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Authors: Steve Reinhardt
* Nathan Binkert
*/
/* @file
* EventQueue interfaces
*/
#ifndef __SIM_EVENTQ_HH__
#define __SIM_EVENTQ_HH__
#include <algorithm>
#include <cassert>
#include <climits>
#include <functional>
#include <iosfwd>
#include <memory>
#include <mutex>
#include <string>
#include "base/flags.hh"
#include "base/types.hh"
#include "debug/Event.hh"
#include "sim/serialize.hh"
class EventQueue; // forward declaration
class BaseGlobalEvent;
//! Simulation Quantum for multiple eventq simulation.
//! The quantum value is the period length after which the queues
//! synchronize themselves with each other. This means that any
//! event to scheduled on Queue A which is generated by an event on
//! Queue B should be at least simQuantum ticks away in future.
extern Tick simQuantum;
//! Current number of allocated main event queues.
extern uint32_t numMainEventQueues;
//! Array for main event queues.
extern std::vector<EventQueue *> mainEventQueue;
//! The current event queue for the running thread. Access to this queue
//! does not require any locking from the thread.
extern __thread EventQueue *_curEventQueue;
//! Current mode of execution: parallel / serial
extern bool inParallelMode;
//! Function for returning eventq queue for the provided
//! index. The function allocates a new queue in case one
//! does not exist for the index, provided that the index
//! is with in bounds.
EventQueue *getEventQueue(uint32_t index);
inline EventQueue *curEventQueue() { return _curEventQueue; }
inline void curEventQueue(EventQueue *q) { _curEventQueue = q; }
/**
* Common base class for Event and GlobalEvent, so they can share flag
* and priority definitions and accessor functions. This class should
* not be used directly.
*/
class EventBase
{
protected:
typedef unsigned short FlagsType;
typedef ::Flags<FlagsType> Flags;
static const FlagsType PublicRead = 0x003f; // public readable flags
static const FlagsType PublicWrite = 0x001d; // public writable flags
static const FlagsType Squashed = 0x0001; // has been squashed
static const FlagsType Scheduled = 0x0002; // has been scheduled
static const FlagsType Managed = 0x0004; // Use life cycle manager
static const FlagsType AutoDelete = Managed; // delete after dispatch
/**
* This used to be AutoSerialize. This value can't be reused
* without changing the checkpoint version since the flag field
* gets serialized.
*/
static const FlagsType Reserved0 = 0x0008;
static const FlagsType IsExitEvent = 0x0010; // special exit event
static const FlagsType IsMainQueue = 0x0020; // on main event queue
static const FlagsType Initialized = 0x7a40; // somewhat random bits
static const FlagsType InitMask = 0xffc0; // mask for init bits
public:
typedef int8_t Priority;
/// Event priorities, to provide tie-breakers for events scheduled
/// at the same cycle. Most events are scheduled at the default
/// priority; these values are used to control events that need to
/// be ordered within a cycle.
/// Minimum priority
static const Priority Minimum_Pri = SCHAR_MIN;
/// If we enable tracing on a particular cycle, do that as the
/// very first thing so we don't miss any of the events on
/// that cycle (even if we enter the debugger).
static const Priority Debug_Enable_Pri = -101;
/// Breakpoints should happen before anything else (except
/// enabling trace output), so we don't miss any action when
/// debugging.
static const Priority Debug_Break_Pri = -100;
/// CPU switches schedule the new CPU's tick event for the
/// same cycle (after unscheduling the old CPU's tick event).
/// The switch needs to come before any tick events to make
/// sure we don't tick both CPUs in the same cycle.
static const Priority CPU_Switch_Pri = -31;
/// For some reason "delayed" inter-cluster writebacks are
/// scheduled before regular writebacks (which have default
/// priority). Steve?
static const Priority Delayed_Writeback_Pri = -1;
/// Default is zero for historical reasons.
static const Priority Default_Pri = 0;
/// DVFS update event leads to stats dump therefore given a lower priority
/// to ensure all relevant states have been updated
static const Priority DVFS_Update_Pri = 31;
/// Serailization needs to occur before tick events also, so
/// that a serialize/unserialize is identical to an on-line
/// CPU switch.
static const Priority Serialize_Pri = 32;
/// CPU ticks must come after other associated CPU events
/// (such as writebacks).
static const Priority CPU_Tick_Pri = 50;
/// If we want to exit a thread in a CPU, it comes after CPU_Tick_Pri
static const Priority CPU_Exit_Pri = 64;
/// Statistics events (dump, reset, etc.) come after
/// everything else, but before exit.
static const Priority Stat_Event_Pri = 90;
/// Progress events come at the end.
static const Priority Progress_Event_Pri = 95;
/// If we want to exit on this cycle, it's the very last thing
/// we do.
static const Priority Sim_Exit_Pri = 100;
/// Maximum priority
static const Priority Maximum_Pri = SCHAR_MAX;
};
/*
* An item on an event queue. The action caused by a given
* event is specified by deriving a subclass and overriding the
* process() member function.
*
* Caution, the order of members is chosen to maximize data packing.
*/
class Event : public EventBase, public Serializable
{
friend class EventQueue;
private:
// The event queue is now a linked list of linked lists. The
// 'nextBin' pointer is to find the bin, where a bin is defined as
// when+priority. All events in the same bin will be stored in a
// second linked list (a stack) maintained by the 'nextInBin'
// pointer. The list will be accessed in LIFO order. The end
// result is that the insert/removal in 'nextBin' is
// linear/constant, and the lookup/removal in 'nextInBin' is
// constant/constant. Hopefully this is a significant improvement
// over the current fully linear insertion.
Event *nextBin;
Event *nextInBin;
static Event *insertBefore(Event *event, Event *curr);
static Event *removeItem(Event *event, Event *last);
Tick _when; //!< timestamp when event should be processed
Priority _priority; //!< event priority
Flags flags;
#ifndef NDEBUG
/// Global counter to generate unique IDs for Event instances
static Counter instanceCounter;
/// This event's unique ID. We can also use pointer values for
/// this but they're not consistent across runs making debugging
/// more difficult. Thus we use a global counter value when
/// debugging.
Counter instance;
/// queue to which this event belongs (though it may or may not be
/// scheduled on this queue yet)
EventQueue *queue;
#endif
#ifdef EVENTQ_DEBUG
Tick whenCreated; //!< time created
Tick whenScheduled; //!< time scheduled
#endif
void
setWhen(Tick when, EventQueue *q)
{
_when = when;
#ifndef NDEBUG
queue = q;
#endif
#ifdef EVENTQ_DEBUG
whenScheduled = curTick();
#endif
}
bool
initialized() const
{
return (flags & InitMask) == Initialized;
}
protected:
/// Accessor for flags.
Flags
getFlags() const
{
return flags & PublicRead;
}
bool
isFlagSet(Flags _flags) const
{
assert(_flags.noneSet(~PublicRead));
return flags.isSet(_flags);
}
/// Accessor for flags.
void
setFlags(Flags _flags)
{
assert(_flags.noneSet(~PublicWrite));
flags.set(_flags);
}
void
clearFlags(Flags _flags)
{
assert(_flags.noneSet(~PublicWrite));
flags.clear(_flags);
}
void
clearFlags()
{
flags.clear(PublicWrite);
}
// This function isn't really useful if TRACING_ON is not defined
virtual void trace(const char *action); //!< trace event activity
protected: /* Memory management */
/**
* @{
* Memory management hooks for events that have the Managed flag set
*
* Events can use automatic memory management by setting the
* Managed flag. The default implementation automatically deletes
* events once they have been removed from the event queue. This
* typically happens when events are descheduled or have been
* triggered and not rescheduled.
*
* The methods below may be overridden by events that need custom
* memory management. For example, events exported to Python need
* to impement reference counting to ensure that the Python
* implementation of the event is kept alive while it lives in the
* event queue.
*
* @note Memory managers are responsible for implementing
* reference counting (by overriding both acquireImpl() and
* releaseImpl()) or checking if an event is no longer scheduled
* in releaseImpl() before deallocating it.
*/
/**
* Managed event scheduled and being held in the event queue.
*/
void acquire()
{
if (flags.isSet(Event::Managed))
acquireImpl();
}
/**
* Managed event removed from the event queue.
*/
void release() {
if (flags.isSet(Event::Managed))
releaseImpl();
}
virtual void acquireImpl() {}
virtual void releaseImpl() {
if (!scheduled())
delete this;
}
/** @} */
public:
/*
* Event constructor
* @param queue that the event gets scheduled on
*/
Event(Priority p = Default_Pri, Flags f = 0)
: nextBin(nullptr), nextInBin(nullptr), _when(0), _priority(p),
flags(Initialized | f)
{
assert(f.noneSet(~PublicWrite));
#ifndef NDEBUG
instance = ++instanceCounter;
queue = NULL;
#endif
#ifdef EVENTQ_DEBUG
whenCreated = curTick();
whenScheduled = 0;
#endif
}
virtual ~Event();
virtual const std::string name() const;
/// Return a C string describing the event. This string should
/// *not* be dynamically allocated; just a const char array
/// describing the event class.
virtual const char *description() const;
/// Dump the current event data
void dump() const;
public:
/*
* This member function is invoked when the event is processed
* (occurs). There is no default implementation; each subclass
* must provide its own implementation. The event is not
* automatically deleted after it is processed (to allow for
* statically allocated event objects).
*
* If the AutoDestroy flag is set, the object is deleted once it
* is processed.
*/
virtual void process() = 0;
/// Determine if the current event is scheduled
bool scheduled() const { return flags.isSet(Scheduled); }
/// Squash the current event
void squash() { flags.set(Squashed); }
/// Check whether the event is squashed
bool squashed() const { return flags.isSet(Squashed); }
/// See if this is a SimExitEvent (without resorting to RTTI)
bool isExitEvent() const { return flags.isSet(IsExitEvent); }
/// Check whether this event will auto-delete
bool isManaged() const { return flags.isSet(Managed); }
bool isAutoDelete() const { return isManaged(); }
/// Get the time that the event is scheduled
Tick when() const { return _when; }
/// Get the event priority
Priority priority() const { return _priority; }
//! If this is part of a GlobalEvent, return the pointer to the
//! Global Event. By default, there is no GlobalEvent, so return
//! NULL. (Overridden in GlobalEvent::BarrierEvent.)
virtual BaseGlobalEvent *globalEvent() { return NULL; }
void serialize(CheckpointOut &cp) const override;
void unserialize(CheckpointIn &cp) override;
};
inline bool
operator<(const Event &l, const Event &r)
{
return l.when() < r.when() ||
(l.when() == r.when() && l.priority() < r.priority());
}
inline bool
operator>(const Event &l, const Event &r)
{
return l.when() > r.when() ||
(l.when() == r.when() && l.priority() > r.priority());
}
inline bool
operator<=(const Event &l, const Event &r)
{
return l.when() < r.when() ||
(l.when() == r.when() && l.priority() <= r.priority());
}
inline bool
operator>=(const Event &l, const Event &r)
{
return l.when() > r.when() ||
(l.when() == r.when() && l.priority() >= r.priority());
}
inline bool
operator==(const Event &l, const Event &r)
{
return l.when() == r.when() && l.priority() == r.priority();
}
inline bool
operator!=(const Event &l, const Event &r)
{
return l.when() != r.when() || l.priority() != r.priority();
}
/**
* Queue of events sorted in time order
*
* Events are scheduled (inserted into the event queue) using the
* schedule() method. This method either inserts a <i>synchronous</i>
* or <i>asynchronous</i> 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 <i>never</i> 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().
*/
class EventQueue
{
private:
std::string objName;
Event *head;
Tick _curTick;
//! Mutex to protect async queue.
std::mutex async_queue_mutex;
//! List of events added by other threads to this event queue.
std::list<Event*> async_queue;
/**
* 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 EventQueue::ScopedMigration.
* @see EventQueue::ScopedRelease
* @see EventQueue::lock()
* @see EventQueue::unlock()
*/
std::mutex service_mutex;
//! Insert / remove event from the queue. Should only be called
//! by thread operating this queue.
void insert(Event *event);
void remove(Event *event);
//! 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().
void asyncInsert(Event *event);
EventQueue(const EventQueue &);
public:
/**
* Temporarily migrate execution to a different event queue.
*
* An instance of this class temporarily migrates execution to a
* different event queue by releasing the current queue, locking
* the new queue, and updating curEventQueue(). This can, for
* example, be useful when performing IO across thread event
* queues when timing is not crucial (e.g., during fast
* forwarding).
*
* ScopedMigration does nothing if both eqs are the same
*/
class ScopedMigration
{
public:
ScopedMigration(EventQueue *_new_eq, bool _doMigrate = true)
:new_eq(*_new_eq), old_eq(*curEventQueue()),
doMigrate((&new_eq != &old_eq)&&_doMigrate)
{
if (doMigrate){
old_eq.unlock();
new_eq.lock();
curEventQueue(&new_eq);
}
}
~ScopedMigration()
{
if (doMigrate){
new_eq.unlock();
old_eq.lock();
curEventQueue(&old_eq);
}
}
private:
EventQueue &new_eq;
EventQueue &old_eq;
bool doMigrate;
};
/**
* Temporarily release the event queue service lock.
*
* There are cases where it is desirable to temporarily release
* the event queue lock to prevent deadlocks. For example, when
* waiting on the global barrier, we need to release the lock to
* prevent deadlocks from happening when another thread tries to
* temporarily take over the event queue waiting on the barrier.
*/
class ScopedRelease
{
public:
ScopedRelease(EventQueue *_eq)
: eq(*_eq)
{
eq.unlock();
}
~ScopedRelease()
{
eq.lock();
}
private:
EventQueue &eq;
};
EventQueue(const std::string &n);
virtual const std::string name() const { return objName; }
void name(const std::string &st) { objName = st; }
//! Schedule the given event on this queue. Safe to call from any
//! thread.
void schedule(Event *event, Tick when, bool global = false);
//! Deschedule the specified event. Should be called only from the
//! owning thread.
void deschedule(Event *event);
//! Reschedule the specified event. Should be called only from
//! the owning thread.
void reschedule(Event *event, Tick when, bool always = false);
Tick nextTick() const { return head->when(); }
void setCurTick(Tick newVal) { _curTick = newVal; }
Tick getCurTick() const { return _curTick; }
Event *getHead() const { return head; }
Event *serviceOne();
// process all events up to the given timestamp. we inline a
// quick test to see if there are any events to process; if so,
// call the internal out-of-line version to process them all.
void
serviceEvents(Tick when)
{
while (!empty()) {
if (nextTick() > when)
break;
/**
* @todo this assert is a good bug catcher. I need to
* make it true again.
*/
//assert(head->when() >= when && "event scheduled in the past");
serviceOne();
}
setCurTick(when);
}
// return true if no events are queued
bool empty() const { return head == NULL; }
void dump() const;
bool debugVerify() const;
//! Function for moving events from the async_queue to the main queue.
void handleAsyncInsertions();
/**
* 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.
* This function isn't needed by the usual gem5 event loop but may
* be necessary in derived EventQueues which host gem5 onto other
* schedulers.
*
* @param when Time of a delayed wakeup (if known). This parameter
* can be used by an implementation to schedule a wakeup in the
* future if it is sure it will remain active until then.
* Or it can be ignored and the event queue can be woken up now.
*/
virtual void wakeup(Tick when = (Tick)-1) { }
/**
* 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.
*/
Event* replaceHead(Event* s);
/**@{*/
/**
* 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 EventQueue::ScopedMigration.
* @see EventQueue::ScopedRelease
* @see EventQueue
*/
void lock() { service_mutex.lock(); }
void unlock() { service_mutex.unlock(); }
/**@}*/
/**
* 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.
*/
void checkpointReschedule(Event *event);
virtual ~EventQueue()
{
while (!empty())
deschedule(getHead());
}
};
void dumpMainQueue();
class EventManager
{
protected:
/** A pointer to this object's event queue */
EventQueue *eventq;
public:
EventManager(EventManager &em) : eventq(em.eventq) {}
EventManager(EventManager *em) : eventq(em->eventq) {}
EventManager(EventQueue *eq) : eventq(eq) {}
EventQueue *
eventQueue() const
{
return eventq;
}
void
schedule(Event &event, Tick when)
{
eventq->schedule(&event, when);
}
void
deschedule(Event &event)
{
eventq->deschedule(&event);
}
void
reschedule(Event &event, Tick when, bool always = false)
{
eventq->reschedule(&event, when, always);
}
void
schedule(Event *event, Tick when)
{
eventq->schedule(event, when);
}
void
deschedule(Event *event)
{
eventq->deschedule(event);
}
void
reschedule(Event *event, Tick when, bool always = false)
{
eventq->reschedule(event, when, always);
}
void wakeupEventQueue(Tick when = (Tick)-1)
{
eventq->wakeup(when);
}
void setCurTick(Tick newVal) { eventq->setCurTick(newVal); }
};
template <class T, void (T::* F)()>
class EventWrapper : public Event
{
private:
T *object;
public:
EventWrapper(T *obj, bool del = false, Priority p = Default_Pri)
: Event(p), object(obj)
{
if (del)
setFlags(AutoDelete);
}
EventWrapper(T &obj, bool del = false, Priority p = Default_Pri)
: Event(p), object(&obj)
{
if (del)
setFlags(AutoDelete);
}
void process() { (object->*F)(); }
const std::string
name() const
{
return object->name() + ".wrapped_event";
}
const char *description() const { return "EventWrapped"; }
};
class EventFunctionWrapper : public Event
{
private:
std::function<void(void)> callback;
std::string _name;
public:
EventFunctionWrapper(const std::function<void(void)> &callback,
const std::string &name,
bool del = false,
Priority p = Default_Pri)
: Event(p), callback(callback), _name(name)
{
if (del)
setFlags(AutoDelete);
}
void process() { callback(); }
const std::string
name() const
{
return _name + ".wrapped_function_event";
}
const char *description() const { return "EventFunctionWrapped"; }
};
#endif // __SIM_EVENTQ_HH__