2 * Copyright (c) 2000-2005 The Regents of The University of Michigan
3 * Copyright (c) 2013 Advanced Micro Devices, Inc.
4 * Copyright (c) 2013 Mark D. Hill and David A. Wood
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8 * modification, are permitted provided that the following conditions are
9 * met: redistributions of source code must retain the above copyright
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18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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23 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
24 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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28 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30 * Authors: Steve Reinhardt
35 * EventQueue interfaces
38 #ifndef __SIM_EVENTQ_HH__
39 #define __SIM_EVENTQ_HH__
49 #include "base/flags.hh"
50 #include "base/misc.hh"
51 #include "base/types.hh"
52 #include "debug/Event.hh"
53 #include "sim/serialize.hh"
55 class EventQueue; // forward declaration
56 class BaseGlobalEvent;
58 //! Simulation Quantum for multiple eventq simulation.
59 //! The quantum value is the period length after which the queues
60 //! synchronize themselves with each other. This means that any
61 //! event to scheduled on Queue A which is generated by an event on
62 //! Queue B should be at least simQuantum ticks away in future.
63 extern Tick simQuantum;
65 //! Current number of allocated main event queues.
66 extern uint32_t numMainEventQueues;
68 //! Array for main event queues.
69 extern std::vector<EventQueue *> mainEventQueue;
72 //! The current event queue for the running thread. Access to this queue
73 //! does not require any locking from the thread.
75 extern __thread EventQueue *_curEventQueue;
79 //! Current mode of execution: parallel / serial
80 extern bool inParallelMode;
82 //! Function for returning eventq queue for the provided
83 //! index. The function allocates a new queue in case one
84 //! does not exist for the index, provided that the index
85 //! is with in bounds.
86 EventQueue *getEventQueue(uint32_t index);
88 inline EventQueue *curEventQueue() { return _curEventQueue; }
89 inline void curEventQueue(EventQueue *q) { _curEventQueue = q; }
92 * Common base class for Event and GlobalEvent, so they can share flag
93 * and priority definitions and accessor functions. This class should
94 * not be used directly.
99 typedef unsigned short FlagsType;
100 typedef ::Flags<FlagsType> Flags;
102 static const FlagsType PublicRead = 0x003f; // public readable flags
103 static const FlagsType PublicWrite = 0x001d; // public writable flags
104 static const FlagsType Squashed = 0x0001; // has been squashed
105 static const FlagsType Scheduled = 0x0002; // has been scheduled
106 static const FlagsType AutoDelete = 0x0004; // delete after dispatch
107 static const FlagsType AutoSerialize = 0x0008; // must be serialized
108 static const FlagsType IsExitEvent = 0x0010; // special exit event
109 static const FlagsType IsMainQueue = 0x0020; // on main event queue
110 static const FlagsType Initialized = 0x7a40; // somewhat random bits
111 static const FlagsType InitMask = 0xffc0; // mask for init bits
114 typedef int8_t Priority;
116 /// Event priorities, to provide tie-breakers for events scheduled
117 /// at the same cycle. Most events are scheduled at the default
118 /// priority; these values are used to control events that need to
119 /// be ordered within a cycle.
122 static const Priority Minimum_Pri = SCHAR_MIN;
124 /// If we enable tracing on a particular cycle, do that as the
125 /// very first thing so we don't miss any of the events on
126 /// that cycle (even if we enter the debugger).
127 static const Priority Debug_Enable_Pri = -101;
129 /// Breakpoints should happen before anything else (except
130 /// enabling trace output), so we don't miss any action when
132 static const Priority Debug_Break_Pri = -100;
134 /// CPU switches schedule the new CPU's tick event for the
135 /// same cycle (after unscheduling the old CPU's tick event).
136 /// The switch needs to come before any tick events to make
137 /// sure we don't tick both CPUs in the same cycle.
138 static const Priority CPU_Switch_Pri = -31;
140 /// For some reason "delayed" inter-cluster writebacks are
141 /// scheduled before regular writebacks (which have default
142 /// priority). Steve?
143 static const Priority Delayed_Writeback_Pri = -1;
145 /// Default is zero for historical reasons.
146 static const Priority Default_Pri = 0;
148 /// DVFS update event leads to stats dump therefore given a lower priority
149 /// to ensure all relevant states have been updated
150 static const Priority DVFS_Update_Pri = 31;
152 /// Serailization needs to occur before tick events also, so
153 /// that a serialize/unserialize is identical to an on-line
155 static const Priority Serialize_Pri = 32;
157 /// CPU ticks must come after other associated CPU events
158 /// (such as writebacks).
159 static const Priority CPU_Tick_Pri = 50;
161 /// Statistics events (dump, reset, etc.) come after
162 /// everything else, but before exit.
163 static const Priority Stat_Event_Pri = 90;
165 /// Progress events come at the end.
166 static const Priority Progress_Event_Pri = 95;
168 /// If we want to exit on this cycle, it's the very last thing
170 static const Priority Sim_Exit_Pri = 100;
173 static const Priority Maximum_Pri = SCHAR_MAX;
177 * An item on an event queue. The action caused by a given
178 * event is specified by deriving a subclass and overriding the
179 * process() member function.
181 * Caution, the order of members is chosen to maximize data packing.
183 class Event : public EventBase, public Serializable
185 friend class EventQueue;
188 // The event queue is now a linked list of linked lists. The
189 // 'nextBin' pointer is to find the bin, where a bin is defined as
190 // when+priority. All events in the same bin will be stored in a
191 // second linked list (a stack) maintained by the 'nextInBin'
192 // pointer. The list will be accessed in LIFO order. The end
193 // result is that the insert/removal in 'nextBin' is
194 // linear/constant, and the lookup/removal in 'nextInBin' is
195 // constant/constant. Hopefully this is a significant improvement
196 // over the current fully linear insertion.
200 static Event *insertBefore(Event *event, Event *curr);
201 static Event *removeItem(Event *event, Event *last);
203 Tick _when; //!< timestamp when event should be processed
204 Priority _priority; //!< event priority
208 /// Global counter to generate unique IDs for Event instances
209 static Counter instanceCounter;
211 /// This event's unique ID. We can also use pointer values for
212 /// this but they're not consistent across runs making debugging
213 /// more difficult. Thus we use a global counter value when
217 /// queue to which this event belongs (though it may or may not be
218 /// scheduled on this queue yet)
223 Tick whenCreated; //!< time created
224 Tick whenScheduled; //!< time scheduled
228 setWhen(Tick when, EventQueue *q)
235 whenScheduled = curTick();
242 return (flags & InitMask) == Initialized;
246 /// Accessor for flags.
250 return flags & PublicRead;
254 isFlagSet(Flags _flags) const
256 assert(_flags.noneSet(~PublicRead));
257 return flags.isSet(_flags);
260 /// Accessor for flags.
262 setFlags(Flags _flags)
264 assert(_flags.noneSet(~PublicWrite));
269 clearFlags(Flags _flags)
271 assert(_flags.noneSet(~PublicWrite));
278 flags.clear(PublicWrite);
281 // This function isn't really useful if TRACING_ON is not defined
282 virtual void trace(const char *action); //!< trace event activity
288 * @param queue that the event gets scheduled on
290 Event(Priority p = Default_Pri, Flags f = 0)
291 : nextBin(nullptr), nextInBin(nullptr), _when(0), _priority(p),
292 flags(Initialized | f)
294 assert(f.noneSet(~PublicWrite));
296 instance = ++instanceCounter;
300 whenCreated = curTick();
306 virtual const std::string name() const;
308 /// Return a C string describing the event. This string should
309 /// *not* be dynamically allocated; just a const char array
310 /// describing the event class.
311 virtual const char *description() const;
313 /// Dump the current event data
318 * This member function is invoked when the event is processed
319 * (occurs). There is no default implementation; each subclass
320 * must provide its own implementation. The event is not
321 * automatically deleted after it is processed (to allow for
322 * statically allocated event objects).
324 * If the AutoDestroy flag is set, the object is deleted once it
327 virtual void process() = 0;
329 /// Determine if the current event is scheduled
330 bool scheduled() const { return flags.isSet(Scheduled); }
332 /// Squash the current event
333 void squash() { flags.set(Squashed); }
335 /// Check whether the event is squashed
336 bool squashed() const { return flags.isSet(Squashed); }
338 /// See if this is a SimExitEvent (without resorting to RTTI)
339 bool isExitEvent() const { return flags.isSet(IsExitEvent); }
341 /// Get the time that the event is scheduled
342 Tick when() const { return _when; }
344 /// Get the event priority
345 Priority priority() const { return _priority; }
347 //! If this is part of a GlobalEvent, return the pointer to the
348 //! Global Event. By default, there is no GlobalEvent, so return
349 //! NULL. (Overridden in GlobalEvent::BarrierEvent.)
350 virtual BaseGlobalEvent *globalEvent() { return NULL; }
353 void serialize(CheckpointOut &cp) const M5_ATTR_OVERRIDE;
354 void unserialize(CheckpointIn &cp) M5_ATTR_OVERRIDE;
360 operator<(const Event &l, const Event &r)
362 return l.when() < r.when() ||
363 (l.when() == r.when() && l.priority() < r.priority());
367 operator>(const Event &l, const Event &r)
369 return l.when() > r.when() ||
370 (l.when() == r.when() && l.priority() > r.priority());
374 operator<=(const Event &l, const Event &r)
376 return l.when() < r.when() ||
377 (l.when() == r.when() && l.priority() <= r.priority());
380 operator>=(const Event &l, const Event &r)
382 return l.when() > r.when() ||
383 (l.when() == r.when() && l.priority() >= r.priority());
387 operator==(const Event &l, const Event &r)
389 return l.when() == r.when() && l.priority() == r.priority();
393 operator!=(const Event &l, const Event &r)
395 return l.when() != r.when() || l.priority() != r.priority();
400 * Queue of events sorted in time order
402 * Events are scheduled (inserted into the event queue) using the
403 * schedule() method. This method either inserts a <i>synchronous</i>
404 * or <i>asynchronous</i> event.
406 * Synchronous events are scheduled using schedule() method with the
407 * argument 'global' set to false (default). This should only be done
408 * from a thread holding the event queue lock
409 * (EventQueue::service_mutex). The lock is always held when an event
410 * handler is called, it can therefore always insert events into its
411 * own event queue unless it voluntarily releases the lock.
413 * Events can be scheduled across thread (and event queue borders) by
414 * either scheduling asynchronous events or taking the target event
415 * queue's lock. However, the lock should <i>never</i> be taken
416 * directly since this is likely to cause deadlocks. Instead, code
417 * that needs to schedule events in other event queues should
418 * temporarily release its own queue and lock the new queue. This
419 * prevents deadlocks since a single thread never owns more than one
420 * event queue lock. This functionality is provided by the
421 * ScopedMigration helper class. Note that temporarily migrating
422 * between event queues can make the simulation non-deterministic, it
423 * should therefore be limited to cases where that can be tolerated
424 * (e.g., handling asynchronous IO or fast-forwarding in KVM).
426 * Asynchronous events can also be scheduled using the normal
427 * schedule() method with the 'global' parameter set to true. Unlike
428 * the previous queue migration strategy, this strategy is fully
429 * deterministic. This causes the event to be inserted in a separate
430 * queue of asynchronous events (async_queue), which is merged main
431 * event queue at the end of each simulation quantum (by calling the
432 * handleAsyncInsertions() method). Note that this implies that such
433 * events must happen at least one simulation quantum into the future,
434 * otherwise they risk being scheduled in the past by
435 * handleAsyncInsertions().
437 class EventQueue : public Serializable
444 //! Mutex to protect async queue.
445 std::mutex async_queue_mutex;
447 //! List of events added by other threads to this event queue.
448 std::list<Event*> async_queue;
451 * Lock protecting event handling.
453 * This lock is always taken when servicing events. It is assumed
454 * that the thread scheduling new events (not asynchronous events
455 * though) have taken this lock. This is normally done by
456 * serviceOne() since new events are typically scheduled as a
457 * response to an earlier event.
459 * This lock is intended to be used to temporarily steal an event
460 * queue to support inter-thread communication when some
461 * deterministic timing can be sacrificed for speed. For example,
462 * the KVM CPU can use this support to access devices running in a
465 * @see EventQueue::ScopedMigration.
466 * @see EventQueue::ScopedRelease
467 * @see EventQueue::lock()
468 * @see EventQueue::unlock()
470 std::mutex service_mutex;
472 //! Insert / remove event from the queue. Should only be called
473 //! by thread operating this queue.
474 void insert(Event *event);
475 void remove(Event *event);
477 //! Function for adding events to the async queue. The added events
478 //! are added to main event queue later. Threads, other than the
479 //! owning thread, should call this function instead of insert().
480 void asyncInsert(Event *event);
482 EventQueue(const EventQueue &);
487 * Temporarily migrate execution to a different event queue.
489 * An instance of this class temporarily migrates execution to a
490 * different event queue by releasing the current queue, locking
491 * the new queue, and updating curEventQueue(). This can, for
492 * example, be useful when performing IO across thread event
493 * queues when timing is not crucial (e.g., during fast
496 class ScopedMigration
499 ScopedMigration(EventQueue *_new_eq)
500 : new_eq(*_new_eq), old_eq(*curEventQueue())
504 curEventQueue(&new_eq);
511 curEventQueue(&old_eq);
520 * Temporarily release the event queue service lock.
522 * There are cases where it is desirable to temporarily release
523 * the event queue lock to prevent deadlocks. For example, when
524 * waiting on the global barrier, we need to release the lock to
525 * prevent deadlocks from happening when another thread tries to
526 * temporarily take over the event queue waiting on the barrier.
531 ScopedRelease(EventQueue *_eq)
547 EventQueue(const std::string &n);
549 virtual const std::string name() const { return objName; }
550 void name(const std::string &st) { objName = st; }
552 //! Schedule the given event on this queue. Safe to call from any
554 void schedule(Event *event, Tick when, bool global = false);
556 //! Deschedule the specified event. Should be called only from the
558 void deschedule(Event *event);
560 //! Reschedule the specified event. Should be called only from
561 //! the owning thread.
562 void reschedule(Event *event, Tick when, bool always = false);
564 Tick nextTick() const { return head->when(); }
565 void setCurTick(Tick newVal) { _curTick = newVal; }
566 Tick getCurTick() { return _curTick; }
567 Event *getHead() const { return head; }
571 // process all events up to the given timestamp. we inline a
572 // quick test to see if there are any events to process; if so,
573 // call the internal out-of-line version to process them all.
575 serviceEvents(Tick when)
578 if (nextTick() > when)
582 * @todo this assert is a good bug catcher. I need to
583 * make it true again.
585 //assert(head->when() >= when && "event scheduled in the past");
592 // return true if no events are queued
593 bool empty() const { return head == NULL; }
597 bool debugVerify() const;
599 //! Function for moving events from the async_queue to the main queue.
600 void handleAsyncInsertions();
603 * Function to signal that the event loop should be woken up because
604 * an event has been scheduled by an agent outside the gem5 event
605 * loop(s) whose event insertion may not have been noticed by gem5.
606 * This function isn't needed by the usual gem5 event loop but may
607 * be necessary in derived EventQueues which host gem5 onto other
610 * @param when Time of a delayed wakeup (if known). This parameter
611 * can be used by an implementation to schedule a wakeup in the
612 * future if it is sure it will remain active until then.
613 * Or it can be ignored and the event queue can be woken up now.
615 virtual void wakeup(Tick when = (Tick)-1) { }
618 * function for replacing the head of the event queue, so that a
619 * different set of events can run without disturbing events that have
620 * already been scheduled. Already scheduled events can be processed
621 * by replacing the original head back.
622 * USING THIS FUNCTION CAN BE DANGEROUS TO THE HEALTH OF THE SIMULATOR.
623 * NOT RECOMMENDED FOR USE.
625 Event* replaceHead(Event* s);
629 * Provide an interface for locking/unlocking the event queue.
631 * @warn Do NOT use these methods directly unless you really know
632 * what you are doing. Incorrect use can easily lead to simulator
635 * @see EventQueue::ScopedMigration.
636 * @see EventQueue::ScopedRelease
639 void lock() { service_mutex.lock(); }
640 void unlock() { service_mutex.unlock(); }
644 void serialize(CheckpointOut &cp) const M5_ATTR_OVERRIDE;
645 void unserialize(CheckpointIn &cp) M5_ATTR_OVERRIDE;
649 * Reschedule an event after a checkpoint.
651 * Since events don't know which event queue they belong to,
652 * parent objects need to reschedule events themselves. This
653 * method conditionally schedules an event that has the Scheduled
654 * flag set. It should be called by parent objects after
655 * unserializing an object.
657 * @warn Only use this method after unserializing an Event.
659 void checkpointReschedule(Event *event);
661 virtual ~EventQueue() { }
664 void dumpMainQueue();
670 /** A pointer to this object's event queue */
674 EventManager(EventManager &em) : eventq(em.eventq) {}
675 EventManager(EventManager *em) : eventq(em->eventq) {}
676 EventManager(EventQueue *eq) : eventq(eq) {}
685 schedule(Event &event, Tick when)
687 eventq->schedule(&event, when);
691 deschedule(Event &event)
693 eventq->deschedule(&event);
697 reschedule(Event &event, Tick when, bool always = false)
699 eventq->reschedule(&event, when, always);
703 schedule(Event *event, Tick when)
705 eventq->schedule(event, when);
709 deschedule(Event *event)
711 eventq->deschedule(event);
715 reschedule(Event *event, Tick when, bool always = false)
717 eventq->reschedule(event, when, always);
720 void wakeupEventQueue(Tick when = (Tick)-1)
722 eventq->wakeup(when);
725 void setCurTick(Tick newVal) { eventq->setCurTick(newVal); }
728 template <class T, void (T::* F)()>
730 DelayFunction(EventQueue *eventq, Tick when, T *object)
732 class DelayEvent : public Event
739 : Event(Default_Pri, AutoDelete), object(o)
741 void process() { (object->*F)(); }
742 const char *description() const { return "delay"; }
745 eventq->schedule(new DelayEvent(object), when);
748 template <class T, void (T::* F)()>
749 class EventWrapper : public Event
755 EventWrapper(T *obj, bool del = false, Priority p = Default_Pri)
756 : Event(p), object(obj)
759 setFlags(AutoDelete);
762 EventWrapper(T &obj, bool del = false, Priority p = Default_Pri)
763 : Event(p), object(&obj)
766 setFlags(AutoDelete);
769 void process() { (object->*F)(); }
774 return object->name() + ".wrapped_event";
777 const char *description() const { return "EventWrapped"; }
781 #endif // __SIM_EVENTQ_HH__