1/*
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
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions are
9 * met: redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer;
11 * redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution;
14 * neither the name of the copyright holders nor the names of its
15 * contributors may be used to endorse or promote products derived from
16 * this software without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
21 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
22 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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
26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
28 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 *
30 * Authors: Steve Reinhardt
31 * Nathan Binkert
32 */
33
34/* @file
35 * EventQueue interfaces
36 */
37
38#ifndef __SIM_EVENTQ_HH__
39#define __SIM_EVENTQ_HH__
40
41#include <algorithm>
42#include <cassert>
43#include <climits>
44#include <iosfwd>
45#include <memory>
46#include <mutex>
47#include <string>
48
49#include "base/flags.hh"
50#include "base/types.hh"
51#include "debug/Event.hh"
52#include "sim/serialize.hh"
53
54class EventQueue; // forward declaration
55class BaseGlobalEvent;
56
57//! Simulation Quantum for multiple eventq simulation.
58//! The quantum value is the period length after which the queues
59//! synchronize themselves with each other. This means that any
60//! event to scheduled on Queue A which is generated by an event on
61//! Queue B should be at least simQuantum ticks away in future.
62extern Tick simQuantum;
63
64//! Current number of allocated main event queues.
65extern uint32_t numMainEventQueues;
66
67//! Array for main event queues.
68extern std::vector<EventQueue *> mainEventQueue;
69
70#ifndef SWIG
71//! The current event queue for the running thread. Access to this queue
72//! does not require any locking from the thread.
73
74extern __thread EventQueue *_curEventQueue;
75
76#endif
77
78//! Current mode of execution: parallel / serial
79extern bool inParallelMode;
80
81//! Function for returning eventq queue for the provided
82//! index. The function allocates a new queue in case one
83//! does not exist for the index, provided that the index
84//! is with in bounds.
85EventQueue *getEventQueue(uint32_t index);
86
87inline EventQueue *curEventQueue() { return _curEventQueue; }
88inline void curEventQueue(EventQueue *q) { _curEventQueue = q; }
89
90/**
91 * Common base class for Event and GlobalEvent, so they can share flag
92 * and priority definitions and accessor functions. This class should
93 * not be used directly.
94 */
95class EventBase
96{
97 protected:
98 typedef unsigned short FlagsType;
99 typedef ::Flags<FlagsType> Flags;
100
101 static const FlagsType PublicRead = 0x003f; // public readable flags
102 static const FlagsType PublicWrite = 0x001d; // public writable flags
103 static const FlagsType Squashed = 0x0001; // has been squashed
104 static const FlagsType Scheduled = 0x0002; // has been scheduled
105 static const FlagsType AutoDelete = 0x0004; // delete after dispatch
106 /**
107 * This used to be AutoSerialize. This value can't be reused
108 * without changing the checkpoint version since the flag field
109 * gets serialized.
110 */
111 static const FlagsType Reserved0 = 0x0008;
112 static const FlagsType IsExitEvent = 0x0010; // special exit event
113 static const FlagsType IsMainQueue = 0x0020; // on main event queue
114 static const FlagsType Initialized = 0x7a40; // somewhat random bits
115 static const FlagsType InitMask = 0xffc0; // mask for init bits
116
117 public:
118 typedef int8_t Priority;
119
120 /// Event priorities, to provide tie-breakers for events scheduled
121 /// at the same cycle. Most events are scheduled at the default
122 /// priority; these values are used to control events that need to
123 /// be ordered within a cycle.
124
125 /// Minimum priority
126 static const Priority Minimum_Pri = SCHAR_MIN;
127
128 /// If we enable tracing on a particular cycle, do that as the
129 /// very first thing so we don't miss any of the events on
130 /// that cycle (even if we enter the debugger).
131 static const Priority Debug_Enable_Pri = -101;
132
133 /// Breakpoints should happen before anything else (except
134 /// enabling trace output), so we don't miss any action when
135 /// debugging.
136 static const Priority Debug_Break_Pri = -100;
137
138 /// CPU switches schedule the new CPU's tick event for the
139 /// same cycle (after unscheduling the old CPU's tick event).
140 /// The switch needs to come before any tick events to make
141 /// sure we don't tick both CPUs in the same cycle.
142 static const Priority CPU_Switch_Pri = -31;
143
144 /// For some reason "delayed" inter-cluster writebacks are
145 /// scheduled before regular writebacks (which have default
146 /// priority). Steve?
147 static const Priority Delayed_Writeback_Pri = -1;
148
149 /// Default is zero for historical reasons.
150 static const Priority Default_Pri = 0;
151
152 /// DVFS update event leads to stats dump therefore given a lower priority
153 /// to ensure all relevant states have been updated
154 static const Priority DVFS_Update_Pri = 31;
155
156 /// Serailization needs to occur before tick events also, so
157 /// that a serialize/unserialize is identical to an on-line
158 /// CPU switch.
159 static const Priority Serialize_Pri = 32;
160
161 /// CPU ticks must come after other associated CPU events
162 /// (such as writebacks).
163 static const Priority CPU_Tick_Pri = 50;
164
165 /// Statistics events (dump, reset, etc.) come after
166 /// everything else, but before exit.
167 static const Priority Stat_Event_Pri = 90;
168
169 /// Progress events come at the end.
170 static const Priority Progress_Event_Pri = 95;
171
172 /// If we want to exit on this cycle, it's the very last thing
173 /// we do.
174 static const Priority Sim_Exit_Pri = 100;
175
176 /// Maximum priority
177 static const Priority Maximum_Pri = SCHAR_MAX;
178};
179
180/*
181 * An item on an event queue. The action caused by a given
182 * event is specified by deriving a subclass and overriding the
183 * process() member function.
184 *
185 * Caution, the order of members is chosen to maximize data packing.
186 */
187class Event : public EventBase, public Serializable
188{
189 friend class EventQueue;
190
191 private:
192 // The event queue is now a linked list of linked lists. The
193 // 'nextBin' pointer is to find the bin, where a bin is defined as
194 // when+priority. All events in the same bin will be stored in a
195 // second linked list (a stack) maintained by the 'nextInBin'
196 // pointer. The list will be accessed in LIFO order. The end
197 // result is that the insert/removal in 'nextBin' is
198 // linear/constant, and the lookup/removal in 'nextInBin' is
199 // constant/constant. Hopefully this is a significant improvement
200 // over the current fully linear insertion.
201 Event *nextBin;
202 Event *nextInBin;
203
204 static Event *insertBefore(Event *event, Event *curr);
205 static Event *removeItem(Event *event, Event *last);
206
207 Tick _when; //!< timestamp when event should be processed
208 Priority _priority; //!< event priority
209 Flags flags;
210
211#ifndef NDEBUG
212 /// Global counter to generate unique IDs for Event instances
213 static Counter instanceCounter;
214
215 /// This event's unique ID. We can also use pointer values for
216 /// this but they're not consistent across runs making debugging
217 /// more difficult. Thus we use a global counter value when
218 /// debugging.
219 Counter instance;
220
221 /// queue to which this event belongs (though it may or may not be
222 /// scheduled on this queue yet)
223 EventQueue *queue;
224#endif
225
226#ifdef EVENTQ_DEBUG
227 Tick whenCreated; //!< time created
228 Tick whenScheduled; //!< time scheduled
229#endif
230
231 void
232 setWhen(Tick when, EventQueue *q)
233 {
234 _when = when;
235#ifndef NDEBUG
236 queue = q;
237#endif
238#ifdef EVENTQ_DEBUG
239 whenScheduled = curTick();
240#endif
241 }
242
243 bool
244 initialized() const
245 {
246 return (flags & InitMask) == Initialized;
247 }
248
249 protected:
250 /// Accessor for flags.
251 Flags
252 getFlags() const
253 {
254 return flags & PublicRead;
255 }
256
257 bool
258 isFlagSet(Flags _flags) const
259 {
260 assert(_flags.noneSet(~PublicRead));
261 return flags.isSet(_flags);
262 }
263
264 /// Accessor for flags.
265 void
266 setFlags(Flags _flags)
267 {
268 assert(_flags.noneSet(~PublicWrite));
269 flags.set(_flags);
270 }
271
272 void
273 clearFlags(Flags _flags)
274 {
275 assert(_flags.noneSet(~PublicWrite));
276 flags.clear(_flags);
277 }
278
279 void
280 clearFlags()
281 {
282 flags.clear(PublicWrite);
283 }
284
285 // This function isn't really useful if TRACING_ON is not defined
286 virtual void trace(const char *action); //!< trace event activity
287
288 public:
289
290 /*
291 * Event constructor
292 * @param queue that the event gets scheduled on
293 */
294 Event(Priority p = Default_Pri, Flags f = 0)
295 : nextBin(nullptr), nextInBin(nullptr), _when(0), _priority(p),
296 flags(Initialized | f)
297 {
298 assert(f.noneSet(~PublicWrite));
299#ifndef NDEBUG
300 instance = ++instanceCounter;
301 queue = NULL;
302#endif
303#ifdef EVENTQ_DEBUG
304 whenCreated = curTick();
305 whenScheduled = 0;
306#endif
307 }
308
309 virtual ~Event();
310 virtual const std::string name() const;
311
312 /// Return a C string describing the event. This string should
313 /// *not* be dynamically allocated; just a const char array
314 /// describing the event class.
315 virtual const char *description() const;
316
317 /// Dump the current event data
318 void dump() const;
319
320 public:
321 /*
322 * This member function is invoked when the event is processed
323 * (occurs). There is no default implementation; each subclass
324 * must provide its own implementation. The event is not
325 * automatically deleted after it is processed (to allow for
326 * statically allocated event objects).
327 *
328 * If the AutoDestroy flag is set, the object is deleted once it
329 * is processed.
330 */
331 virtual void process() = 0;
332
333 /// Determine if the current event is scheduled
334 bool scheduled() const { return flags.isSet(Scheduled); }
335
336 /// Squash the current event
337 void squash() { flags.set(Squashed); }
338
339 /// Check whether the event is squashed
340 bool squashed() const { return flags.isSet(Squashed); }
341
342 /// See if this is a SimExitEvent (without resorting to RTTI)
343 bool isExitEvent() const { return flags.isSet(IsExitEvent); }
344
345 /// Check whether this event will auto-delete
346 bool isAutoDelete() const { return flags.isSet(AutoDelete); }
347
348 /// Get the time that the event is scheduled
349 Tick when() const { return _when; }
350
351 /// Get the event priority
352 Priority priority() const { return _priority; }
353
354 //! If this is part of a GlobalEvent, return the pointer to the
355 //! Global Event. By default, there is no GlobalEvent, so return
356 //! NULL. (Overridden in GlobalEvent::BarrierEvent.)
357 virtual BaseGlobalEvent *globalEvent() { return NULL; }
358
359#ifndef SWIG
360 void serialize(CheckpointOut &cp) const override;
361 void unserialize(CheckpointIn &cp) override;
362#endif
363};
364
365#ifndef SWIG
366inline bool
367operator<(const Event &l, const Event &r)
368{
369 return l.when() < r.when() ||
370 (l.when() == r.when() && l.priority() < r.priority());
371}
372
373inline bool
374operator>(const Event &l, const Event &r)
375{
376 return l.when() > r.when() ||
377 (l.when() == r.when() && l.priority() > r.priority());
378}
379
380inline bool
381operator<=(const Event &l, const Event &r)
382{
383 return l.when() < r.when() ||
384 (l.when() == r.when() && l.priority() <= r.priority());
385}
386inline bool
387operator>=(const Event &l, const Event &r)
388{
389 return l.when() > r.when() ||
390 (l.when() == r.when() && l.priority() >= r.priority());
391}
392
393inline bool
394operator==(const Event &l, const Event &r)
395{
396 return l.when() == r.when() && l.priority() == r.priority();
397}
398
399inline bool
400operator!=(const Event &l, const Event &r)
401{
402 return l.when() != r.when() || l.priority() != r.priority();
403}
404#endif
405
406/**
407 * Queue of events sorted in time order
408 *
409 * Events are scheduled (inserted into the event queue) using the
410 * schedule() method. This method either inserts a <i>synchronous</i>
411 * or <i>asynchronous</i> event.
412 *
413 * Synchronous events are scheduled using schedule() method with the
414 * argument 'global' set to false (default). This should only be done
415 * from a thread holding the event queue lock
416 * (EventQueue::service_mutex). The lock is always held when an event
417 * handler is called, it can therefore always insert events into its
418 * own event queue unless it voluntarily releases the lock.
419 *
420 * Events can be scheduled across thread (and event queue borders) by
421 * either scheduling asynchronous events or taking the target event
422 * queue's lock. However, the lock should <i>never</i> be taken
423 * directly since this is likely to cause deadlocks. Instead, code
424 * that needs to schedule events in other event queues should
425 * temporarily release its own queue and lock the new queue. This
426 * prevents deadlocks since a single thread never owns more than one
427 * event queue lock. This functionality is provided by the
428 * ScopedMigration helper class. Note that temporarily migrating
429 * between event queues can make the simulation non-deterministic, it
430 * should therefore be limited to cases where that can be tolerated
431 * (e.g., handling asynchronous IO or fast-forwarding in KVM).
432 *
433 * Asynchronous events can also be scheduled using the normal
434 * schedule() method with the 'global' parameter set to true. Unlike
435 * the previous queue migration strategy, this strategy is fully
436 * deterministic. This causes the event to be inserted in a separate
437 * queue of asynchronous events (async_queue), which is merged main
438 * event queue at the end of each simulation quantum (by calling the
439 * handleAsyncInsertions() method). Note that this implies that such
440 * events must happen at least one simulation quantum into the future,
441 * otherwise they risk being scheduled in the past by
442 * handleAsyncInsertions().
443 */
444class EventQueue
445{
446 private:
447 std::string objName;
448 Event *head;
449 Tick _curTick;
450
451 //! Mutex to protect async queue.
452 std::mutex async_queue_mutex;
453
454 //! List of events added by other threads to this event queue.
455 std::list<Event*> async_queue;
456
457 /**
458 * Lock protecting event handling.
459 *
460 * This lock is always taken when servicing events. It is assumed
461 * that the thread scheduling new events (not asynchronous events
462 * though) have taken this lock. This is normally done by
463 * serviceOne() since new events are typically scheduled as a
464 * response to an earlier event.
465 *
466 * This lock is intended to be used to temporarily steal an event
467 * queue to support inter-thread communication when some
468 * deterministic timing can be sacrificed for speed. For example,
469 * the KVM CPU can use this support to access devices running in a
470 * different thread.
471 *
472 * @see EventQueue::ScopedMigration.
473 * @see EventQueue::ScopedRelease
474 * @see EventQueue::lock()
475 * @see EventQueue::unlock()
476 */
477 std::mutex service_mutex;
478
479 //! Insert / remove event from the queue. Should only be called
480 //! by thread operating this queue.
481 void insert(Event *event);
482 void remove(Event *event);
483
484 //! Function for adding events to the async queue. The added events
485 //! are added to main event queue later. Threads, other than the
486 //! owning thread, should call this function instead of insert().
487 void asyncInsert(Event *event);
488
489 EventQueue(const EventQueue &);
490
491 public:
492#ifndef SWIG
493 /**
494 * Temporarily migrate execution to a different event queue.
495 *
496 * An instance of this class temporarily migrates execution to a
497 * different event queue by releasing the current queue, locking
498 * the new queue, and updating curEventQueue(). This can, for
499 * example, be useful when performing IO across thread event
500 * queues when timing is not crucial (e.g., during fast
501 * forwarding).
502 */
503 class ScopedMigration
504 {
505 public:
506 ScopedMigration(EventQueue *_new_eq)
507 : new_eq(*_new_eq), old_eq(*curEventQueue())
508 {
509 old_eq.unlock();
510 new_eq.lock();
511 curEventQueue(&new_eq);
512 }
513
514 ~ScopedMigration()
515 {
516 new_eq.unlock();
517 old_eq.lock();
518 curEventQueue(&old_eq);
519 }
520
521 private:
522 EventQueue &new_eq;
523 EventQueue &old_eq;
524 };
525
526 /**
527 * Temporarily release the event queue service lock.
528 *
529 * There are cases where it is desirable to temporarily release
530 * the event queue lock to prevent deadlocks. For example, when
531 * waiting on the global barrier, we need to release the lock to
532 * prevent deadlocks from happening when another thread tries to
533 * temporarily take over the event queue waiting on the barrier.
534 */
535 class ScopedRelease
536 {
537 public:
538 ScopedRelease(EventQueue *_eq)
539 : eq(*_eq)
540 {
541 eq.unlock();
542 }
543
544 ~ScopedRelease()
545 {
546 eq.lock();
547 }
548
549 private:
550 EventQueue &eq;
551 };
552#endif
553
554 EventQueue(const std::string &n);
555
556 virtual const std::string name() const { return objName; }
557 void name(const std::string &st) { objName = st; }
558
559 //! Schedule the given event on this queue. Safe to call from any
560 //! thread.
561 void schedule(Event *event, Tick when, bool global = false);
562
563 //! Deschedule the specified event. Should be called only from the
564 //! owning thread.
565 void deschedule(Event *event);
566
567 //! Reschedule the specified event. Should be called only from
568 //! the owning thread.
569 void reschedule(Event *event, Tick when, bool always = false);
570
571 Tick nextTick() const { return head->when(); }
572 void setCurTick(Tick newVal) { _curTick = newVal; }
573 Tick getCurTick() const { return _curTick; }
574 Event *getHead() const { return head; }
575
576 Event *serviceOne();
577
578 // process all events up to the given timestamp. we inline a
579 // quick test to see if there are any events to process; if so,
580 // call the internal out-of-line version to process them all.
581 void
582 serviceEvents(Tick when)
583 {
584 while (!empty()) {
585 if (nextTick() > when)
586 break;
587
588 /**
589 * @todo this assert is a good bug catcher. I need to
590 * make it true again.
591 */
592 //assert(head->when() >= when && "event scheduled in the past");
593 serviceOne();
594 }
595
596 setCurTick(when);
597 }
598
599 // return true if no events are queued
600 bool empty() const { return head == NULL; }
601
602 void dump() const;
603
604 bool debugVerify() const;
605
606 //! Function for moving events from the async_queue to the main queue.
607 void handleAsyncInsertions();
608
609 /**
610 * Function to signal that the event loop should be woken up because
611 * an event has been scheduled by an agent outside the gem5 event
612 * loop(s) whose event insertion may not have been noticed by gem5.
613 * This function isn't needed by the usual gem5 event loop but may
614 * be necessary in derived EventQueues which host gem5 onto other
615 * schedulers.
616 *
617 * @param when Time of a delayed wakeup (if known). This parameter
618 * can be used by an implementation to schedule a wakeup in the
619 * future if it is sure it will remain active until then.
620 * Or it can be ignored and the event queue can be woken up now.
621 */
622 virtual void wakeup(Tick when = (Tick)-1) { }
623
624 /**
625 * function for replacing the head of the event queue, so that a
626 * different set of events can run without disturbing events that have
627 * already been scheduled. Already scheduled events can be processed
628 * by replacing the original head back.
629 * USING THIS FUNCTION CAN BE DANGEROUS TO THE HEALTH OF THE SIMULATOR.
630 * NOT RECOMMENDED FOR USE.
631 */
632 Event* replaceHead(Event* s);
633
634 /**@{*/
635 /**
636 * Provide an interface for locking/unlocking the event queue.
637 *
638 * @warn Do NOT use these methods directly unless you really know
639 * what you are doing. Incorrect use can easily lead to simulator
640 * deadlocks.
641 *
642 * @see EventQueue::ScopedMigration.
643 * @see EventQueue::ScopedRelease
644 * @see EventQueue
645 */
646 void lock() { service_mutex.lock(); }
647 void unlock() { service_mutex.unlock(); }
648 /**@}*/
649
650 /**
651 * Reschedule an event after a checkpoint.
652 *
653 * Since events don't know which event queue they belong to,
654 * parent objects need to reschedule events themselves. This
655 * method conditionally schedules an event that has the Scheduled
656 * flag set. It should be called by parent objects after
657 * unserializing an object.
658 *
659 * @warn Only use this method after unserializing an Event.
660 */
661 void checkpointReschedule(Event *event);
662
663 virtual ~EventQueue() { }
664};
665
666void dumpMainQueue();
667
668#ifndef SWIG
669class EventManager
670{
671 protected:
672 /** A pointer to this object's event queue */
673 EventQueue *eventq;
674
675 public:
676 EventManager(EventManager &em) : eventq(em.eventq) {}
677 EventManager(EventManager *em) : eventq(em->eventq) {}
678 EventManager(EventQueue *eq) : eventq(eq) {}
679
680 EventQueue *
681 eventQueue() const
682 {
683 return eventq;
684 }
685
686 void
687 schedule(Event &event, Tick when)
688 {
689 eventq->schedule(&event, when);
690 }
691
692 void
693 deschedule(Event &event)
694 {
695 eventq->deschedule(&event);
696 }
697
698 void
699 reschedule(Event &event, Tick when, bool always = false)
700 {
701 eventq->reschedule(&event, when, always);
702 }
703
704 void
705 schedule(Event *event, Tick when)
706 {
707 eventq->schedule(event, when);
708 }
709
710 void
711 deschedule(Event *event)
712 {
713 eventq->deschedule(event);
714 }
715
716 void
717 reschedule(Event *event, Tick when, bool always = false)
718 {
719 eventq->reschedule(event, when, always);
720 }
721
722 void wakeupEventQueue(Tick when = (Tick)-1)
723 {
724 eventq->wakeup(when);
725 }
726
727 void setCurTick(Tick newVal) { eventq->setCurTick(newVal); }
728};
729
730template <class T, void (T::* F)()>
731void
732DelayFunction(EventQueue *eventq, Tick when, T *object)
733{
734 class DelayEvent : public Event
735 {
736 private:
737 T *object;
738
739 public:
740 DelayEvent(T *o)
741 : Event(Default_Pri, AutoDelete), object(o)
742 { }
743 void process() { (object->*F)(); }
744 const char *description() const { return "delay"; }
745 };
746
747 eventq->schedule(new DelayEvent(object), when);
748}
749
750template <class T, void (T::* F)()>
751class EventWrapper : public Event
752{
753 private:
754 T *object;
755
756 public:
757 EventWrapper(T *obj, bool del = false, Priority p = Default_Pri)
758 : Event(p), object(obj)
759 {
760 if (del)
761 setFlags(AutoDelete);
762 }
763
764 EventWrapper(T &obj, bool del = false, Priority p = Default_Pri)
765 : Event(p), object(&obj)
766 {
767 if (del)
768 setFlags(AutoDelete);
769 }
770
771 void process() { (object->*F)(); }
772
773 const std::string
774 name() const
775 {
776 return object->name() + ".wrapped_event";
777 }
778
779 const char *description() const { return "EventWrapped"; }
780};
781#endif
782
783#endif // __SIM_EVENTQ_HH__
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
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions are
9 * met: redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer;
11 * redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution;
14 * neither the name of the copyright holders nor the names of its
15 * contributors may be used to endorse or promote products derived from
16 * this software without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
21 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
22 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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
26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
28 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 *
30 * Authors: Steve Reinhardt
31 * Nathan Binkert
32 */
33
34/* @file
35 * EventQueue interfaces
36 */
37
38#ifndef __SIM_EVENTQ_HH__
39#define __SIM_EVENTQ_HH__
40
41#include <algorithm>
42#include <cassert>
43#include <climits>
44#include <iosfwd>
45#include <memory>
46#include <mutex>
47#include <string>
48
49#include "base/flags.hh"
50#include "base/types.hh"
51#include "debug/Event.hh"
52#include "sim/serialize.hh"
53
54class EventQueue; // forward declaration
55class BaseGlobalEvent;
56
57//! Simulation Quantum for multiple eventq simulation.
58//! The quantum value is the period length after which the queues
59//! synchronize themselves with each other. This means that any
60//! event to scheduled on Queue A which is generated by an event on
61//! Queue B should be at least simQuantum ticks away in future.
62extern Tick simQuantum;
63
64//! Current number of allocated main event queues.
65extern uint32_t numMainEventQueues;
66
67//! Array for main event queues.
68extern std::vector<EventQueue *> mainEventQueue;
69
70#ifndef SWIG
71//! The current event queue for the running thread. Access to this queue
72//! does not require any locking from the thread.
73
74extern __thread EventQueue *_curEventQueue;
75
76#endif
77
78//! Current mode of execution: parallel / serial
79extern bool inParallelMode;
80
81//! Function for returning eventq queue for the provided
82//! index. The function allocates a new queue in case one
83//! does not exist for the index, provided that the index
84//! is with in bounds.
85EventQueue *getEventQueue(uint32_t index);
86
87inline EventQueue *curEventQueue() { return _curEventQueue; }
88inline void curEventQueue(EventQueue *q) { _curEventQueue = q; }
89
90/**
91 * Common base class for Event and GlobalEvent, so they can share flag
92 * and priority definitions and accessor functions. This class should
93 * not be used directly.
94 */
95class EventBase
96{
97 protected:
98 typedef unsigned short FlagsType;
99 typedef ::Flags<FlagsType> Flags;
100
101 static const FlagsType PublicRead = 0x003f; // public readable flags
102 static const FlagsType PublicWrite = 0x001d; // public writable flags
103 static const FlagsType Squashed = 0x0001; // has been squashed
104 static const FlagsType Scheduled = 0x0002; // has been scheduled
105 static const FlagsType AutoDelete = 0x0004; // delete after dispatch
106 /**
107 * This used to be AutoSerialize. This value can't be reused
108 * without changing the checkpoint version since the flag field
109 * gets serialized.
110 */
111 static const FlagsType Reserved0 = 0x0008;
112 static const FlagsType IsExitEvent = 0x0010; // special exit event
113 static const FlagsType IsMainQueue = 0x0020; // on main event queue
114 static const FlagsType Initialized = 0x7a40; // somewhat random bits
115 static const FlagsType InitMask = 0xffc0; // mask for init bits
116
117 public:
118 typedef int8_t Priority;
119
120 /// Event priorities, to provide tie-breakers for events scheduled
121 /// at the same cycle. Most events are scheduled at the default
122 /// priority; these values are used to control events that need to
123 /// be ordered within a cycle.
124
125 /// Minimum priority
126 static const Priority Minimum_Pri = SCHAR_MIN;
127
128 /// If we enable tracing on a particular cycle, do that as the
129 /// very first thing so we don't miss any of the events on
130 /// that cycle (even if we enter the debugger).
131 static const Priority Debug_Enable_Pri = -101;
132
133 /// Breakpoints should happen before anything else (except
134 /// enabling trace output), so we don't miss any action when
135 /// debugging.
136 static const Priority Debug_Break_Pri = -100;
137
138 /// CPU switches schedule the new CPU's tick event for the
139 /// same cycle (after unscheduling the old CPU's tick event).
140 /// The switch needs to come before any tick events to make
141 /// sure we don't tick both CPUs in the same cycle.
142 static const Priority CPU_Switch_Pri = -31;
143
144 /// For some reason "delayed" inter-cluster writebacks are
145 /// scheduled before regular writebacks (which have default
146 /// priority). Steve?
147 static const Priority Delayed_Writeback_Pri = -1;
148
149 /// Default is zero for historical reasons.
150 static const Priority Default_Pri = 0;
151
152 /// DVFS update event leads to stats dump therefore given a lower priority
153 /// to ensure all relevant states have been updated
154 static const Priority DVFS_Update_Pri = 31;
155
156 /// Serailization needs to occur before tick events also, so
157 /// that a serialize/unserialize is identical to an on-line
158 /// CPU switch.
159 static const Priority Serialize_Pri = 32;
160
161 /// CPU ticks must come after other associated CPU events
162 /// (such as writebacks).
163 static const Priority CPU_Tick_Pri = 50;
164
165 /// Statistics events (dump, reset, etc.) come after
166 /// everything else, but before exit.
167 static const Priority Stat_Event_Pri = 90;
168
169 /// Progress events come at the end.
170 static const Priority Progress_Event_Pri = 95;
171
172 /// If we want to exit on this cycle, it's the very last thing
173 /// we do.
174 static const Priority Sim_Exit_Pri = 100;
175
176 /// Maximum priority
177 static const Priority Maximum_Pri = SCHAR_MAX;
178};
179
180/*
181 * An item on an event queue. The action caused by a given
182 * event is specified by deriving a subclass and overriding the
183 * process() member function.
184 *
185 * Caution, the order of members is chosen to maximize data packing.
186 */
187class Event : public EventBase, public Serializable
188{
189 friend class EventQueue;
190
191 private:
192 // The event queue is now a linked list of linked lists. The
193 // 'nextBin' pointer is to find the bin, where a bin is defined as
194 // when+priority. All events in the same bin will be stored in a
195 // second linked list (a stack) maintained by the 'nextInBin'
196 // pointer. The list will be accessed in LIFO order. The end
197 // result is that the insert/removal in 'nextBin' is
198 // linear/constant, and the lookup/removal in 'nextInBin' is
199 // constant/constant. Hopefully this is a significant improvement
200 // over the current fully linear insertion.
201 Event *nextBin;
202 Event *nextInBin;
203
204 static Event *insertBefore(Event *event, Event *curr);
205 static Event *removeItem(Event *event, Event *last);
206
207 Tick _when; //!< timestamp when event should be processed
208 Priority _priority; //!< event priority
209 Flags flags;
210
211#ifndef NDEBUG
212 /// Global counter to generate unique IDs for Event instances
213 static Counter instanceCounter;
214
215 /// This event's unique ID. We can also use pointer values for
216 /// this but they're not consistent across runs making debugging
217 /// more difficult. Thus we use a global counter value when
218 /// debugging.
219 Counter instance;
220
221 /// queue to which this event belongs (though it may or may not be
222 /// scheduled on this queue yet)
223 EventQueue *queue;
224#endif
225
226#ifdef EVENTQ_DEBUG
227 Tick whenCreated; //!< time created
228 Tick whenScheduled; //!< time scheduled
229#endif
230
231 void
232 setWhen(Tick when, EventQueue *q)
233 {
234 _when = when;
235#ifndef NDEBUG
236 queue = q;
237#endif
238#ifdef EVENTQ_DEBUG
239 whenScheduled = curTick();
240#endif
241 }
242
243 bool
244 initialized() const
245 {
246 return (flags & InitMask) == Initialized;
247 }
248
249 protected:
250 /// Accessor for flags.
251 Flags
252 getFlags() const
253 {
254 return flags & PublicRead;
255 }
256
257 bool
258 isFlagSet(Flags _flags) const
259 {
260 assert(_flags.noneSet(~PublicRead));
261 return flags.isSet(_flags);
262 }
263
264 /// Accessor for flags.
265 void
266 setFlags(Flags _flags)
267 {
268 assert(_flags.noneSet(~PublicWrite));
269 flags.set(_flags);
270 }
271
272 void
273 clearFlags(Flags _flags)
274 {
275 assert(_flags.noneSet(~PublicWrite));
276 flags.clear(_flags);
277 }
278
279 void
280 clearFlags()
281 {
282 flags.clear(PublicWrite);
283 }
284
285 // This function isn't really useful if TRACING_ON is not defined
286 virtual void trace(const char *action); //!< trace event activity
287
288 public:
289
290 /*
291 * Event constructor
292 * @param queue that the event gets scheduled on
293 */
294 Event(Priority p = Default_Pri, Flags f = 0)
295 : nextBin(nullptr), nextInBin(nullptr), _when(0), _priority(p),
296 flags(Initialized | f)
297 {
298 assert(f.noneSet(~PublicWrite));
299#ifndef NDEBUG
300 instance = ++instanceCounter;
301 queue = NULL;
302#endif
303#ifdef EVENTQ_DEBUG
304 whenCreated = curTick();
305 whenScheduled = 0;
306#endif
307 }
308
309 virtual ~Event();
310 virtual const std::string name() const;
311
312 /// Return a C string describing the event. This string should
313 /// *not* be dynamically allocated; just a const char array
314 /// describing the event class.
315 virtual const char *description() const;
316
317 /// Dump the current event data
318 void dump() const;
319
320 public:
321 /*
322 * This member function is invoked when the event is processed
323 * (occurs). There is no default implementation; each subclass
324 * must provide its own implementation. The event is not
325 * automatically deleted after it is processed (to allow for
326 * statically allocated event objects).
327 *
328 * If the AutoDestroy flag is set, the object is deleted once it
329 * is processed.
330 */
331 virtual void process() = 0;
332
333 /// Determine if the current event is scheduled
334 bool scheduled() const { return flags.isSet(Scheduled); }
335
336 /// Squash the current event
337 void squash() { flags.set(Squashed); }
338
339 /// Check whether the event is squashed
340 bool squashed() const { return flags.isSet(Squashed); }
341
342 /// See if this is a SimExitEvent (without resorting to RTTI)
343 bool isExitEvent() const { return flags.isSet(IsExitEvent); }
344
345 /// Check whether this event will auto-delete
346 bool isAutoDelete() const { return flags.isSet(AutoDelete); }
347
348 /// Get the time that the event is scheduled
349 Tick when() const { return _when; }
350
351 /// Get the event priority
352 Priority priority() const { return _priority; }
353
354 //! If this is part of a GlobalEvent, return the pointer to the
355 //! Global Event. By default, there is no GlobalEvent, so return
356 //! NULL. (Overridden in GlobalEvent::BarrierEvent.)
357 virtual BaseGlobalEvent *globalEvent() { return NULL; }
358
359#ifndef SWIG
360 void serialize(CheckpointOut &cp) const override;
361 void unserialize(CheckpointIn &cp) override;
362#endif
363};
364
365#ifndef SWIG
366inline bool
367operator<(const Event &l, const Event &r)
368{
369 return l.when() < r.when() ||
370 (l.when() == r.when() && l.priority() < r.priority());
371}
372
373inline bool
374operator>(const Event &l, const Event &r)
375{
376 return l.when() > r.when() ||
377 (l.when() == r.when() && l.priority() > r.priority());
378}
379
380inline bool
381operator<=(const Event &l, const Event &r)
382{
383 return l.when() < r.when() ||
384 (l.when() == r.when() && l.priority() <= r.priority());
385}
386inline bool
387operator>=(const Event &l, const Event &r)
388{
389 return l.when() > r.when() ||
390 (l.when() == r.when() && l.priority() >= r.priority());
391}
392
393inline bool
394operator==(const Event &l, const Event &r)
395{
396 return l.when() == r.when() && l.priority() == r.priority();
397}
398
399inline bool
400operator!=(const Event &l, const Event &r)
401{
402 return l.when() != r.when() || l.priority() != r.priority();
403}
404#endif
405
406/**
407 * Queue of events sorted in time order
408 *
409 * Events are scheduled (inserted into the event queue) using the
410 * schedule() method. This method either inserts a <i>synchronous</i>
411 * or <i>asynchronous</i> event.
412 *
413 * Synchronous events are scheduled using schedule() method with the
414 * argument 'global' set to false (default). This should only be done
415 * from a thread holding the event queue lock
416 * (EventQueue::service_mutex). The lock is always held when an event
417 * handler is called, it can therefore always insert events into its
418 * own event queue unless it voluntarily releases the lock.
419 *
420 * Events can be scheduled across thread (and event queue borders) by
421 * either scheduling asynchronous events or taking the target event
422 * queue's lock. However, the lock should <i>never</i> be taken
423 * directly since this is likely to cause deadlocks. Instead, code
424 * that needs to schedule events in other event queues should
425 * temporarily release its own queue and lock the new queue. This
426 * prevents deadlocks since a single thread never owns more than one
427 * event queue lock. This functionality is provided by the
428 * ScopedMigration helper class. Note that temporarily migrating
429 * between event queues can make the simulation non-deterministic, it
430 * should therefore be limited to cases where that can be tolerated
431 * (e.g., handling asynchronous IO or fast-forwarding in KVM).
432 *
433 * Asynchronous events can also be scheduled using the normal
434 * schedule() method with the 'global' parameter set to true. Unlike
435 * the previous queue migration strategy, this strategy is fully
436 * deterministic. This causes the event to be inserted in a separate
437 * queue of asynchronous events (async_queue), which is merged main
438 * event queue at the end of each simulation quantum (by calling the
439 * handleAsyncInsertions() method). Note that this implies that such
440 * events must happen at least one simulation quantum into the future,
441 * otherwise they risk being scheduled in the past by
442 * handleAsyncInsertions().
443 */
444class EventQueue
445{
446 private:
447 std::string objName;
448 Event *head;
449 Tick _curTick;
450
451 //! Mutex to protect async queue.
452 std::mutex async_queue_mutex;
453
454 //! List of events added by other threads to this event queue.
455 std::list<Event*> async_queue;
456
457 /**
458 * Lock protecting event handling.
459 *
460 * This lock is always taken when servicing events. It is assumed
461 * that the thread scheduling new events (not asynchronous events
462 * though) have taken this lock. This is normally done by
463 * serviceOne() since new events are typically scheduled as a
464 * response to an earlier event.
465 *
466 * This lock is intended to be used to temporarily steal an event
467 * queue to support inter-thread communication when some
468 * deterministic timing can be sacrificed for speed. For example,
469 * the KVM CPU can use this support to access devices running in a
470 * different thread.
471 *
472 * @see EventQueue::ScopedMigration.
473 * @see EventQueue::ScopedRelease
474 * @see EventQueue::lock()
475 * @see EventQueue::unlock()
476 */
477 std::mutex service_mutex;
478
479 //! Insert / remove event from the queue. Should only be called
480 //! by thread operating this queue.
481 void insert(Event *event);
482 void remove(Event *event);
483
484 //! Function for adding events to the async queue. The added events
485 //! are added to main event queue later. Threads, other than the
486 //! owning thread, should call this function instead of insert().
487 void asyncInsert(Event *event);
488
489 EventQueue(const EventQueue &);
490
491 public:
492#ifndef SWIG
493 /**
494 * Temporarily migrate execution to a different event queue.
495 *
496 * An instance of this class temporarily migrates execution to a
497 * different event queue by releasing the current queue, locking
498 * the new queue, and updating curEventQueue(). This can, for
499 * example, be useful when performing IO across thread event
500 * queues when timing is not crucial (e.g., during fast
501 * forwarding).
502 */
503 class ScopedMigration
504 {
505 public:
506 ScopedMigration(EventQueue *_new_eq)
507 : new_eq(*_new_eq), old_eq(*curEventQueue())
508 {
509 old_eq.unlock();
510 new_eq.lock();
511 curEventQueue(&new_eq);
512 }
513
514 ~ScopedMigration()
515 {
516 new_eq.unlock();
517 old_eq.lock();
518 curEventQueue(&old_eq);
519 }
520
521 private:
522 EventQueue &new_eq;
523 EventQueue &old_eq;
524 };
525
526 /**
527 * Temporarily release the event queue service lock.
528 *
529 * There are cases where it is desirable to temporarily release
530 * the event queue lock to prevent deadlocks. For example, when
531 * waiting on the global barrier, we need to release the lock to
532 * prevent deadlocks from happening when another thread tries to
533 * temporarily take over the event queue waiting on the barrier.
534 */
535 class ScopedRelease
536 {
537 public:
538 ScopedRelease(EventQueue *_eq)
539 : eq(*_eq)
540 {
541 eq.unlock();
542 }
543
544 ~ScopedRelease()
545 {
546 eq.lock();
547 }
548
549 private:
550 EventQueue &eq;
551 };
552#endif
553
554 EventQueue(const std::string &n);
555
556 virtual const std::string name() const { return objName; }
557 void name(const std::string &st) { objName = st; }
558
559 //! Schedule the given event on this queue. Safe to call from any
560 //! thread.
561 void schedule(Event *event, Tick when, bool global = false);
562
563 //! Deschedule the specified event. Should be called only from the
564 //! owning thread.
565 void deschedule(Event *event);
566
567 //! Reschedule the specified event. Should be called only from
568 //! the owning thread.
569 void reschedule(Event *event, Tick when, bool always = false);
570
571 Tick nextTick() const { return head->when(); }
572 void setCurTick(Tick newVal) { _curTick = newVal; }
573 Tick getCurTick() const { return _curTick; }
574 Event *getHead() const { return head; }
575
576 Event *serviceOne();
577
578 // process all events up to the given timestamp. we inline a
579 // quick test to see if there are any events to process; if so,
580 // call the internal out-of-line version to process them all.
581 void
582 serviceEvents(Tick when)
583 {
584 while (!empty()) {
585 if (nextTick() > when)
586 break;
587
588 /**
589 * @todo this assert is a good bug catcher. I need to
590 * make it true again.
591 */
592 //assert(head->when() >= when && "event scheduled in the past");
593 serviceOne();
594 }
595
596 setCurTick(when);
597 }
598
599 // return true if no events are queued
600 bool empty() const { return head == NULL; }
601
602 void dump() const;
603
604 bool debugVerify() const;
605
606 //! Function for moving events from the async_queue to the main queue.
607 void handleAsyncInsertions();
608
609 /**
610 * Function to signal that the event loop should be woken up because
611 * an event has been scheduled by an agent outside the gem5 event
612 * loop(s) whose event insertion may not have been noticed by gem5.
613 * This function isn't needed by the usual gem5 event loop but may
614 * be necessary in derived EventQueues which host gem5 onto other
615 * schedulers.
616 *
617 * @param when Time of a delayed wakeup (if known). This parameter
618 * can be used by an implementation to schedule a wakeup in the
619 * future if it is sure it will remain active until then.
620 * Or it can be ignored and the event queue can be woken up now.
621 */
622 virtual void wakeup(Tick when = (Tick)-1) { }
623
624 /**
625 * function for replacing the head of the event queue, so that a
626 * different set of events can run without disturbing events that have
627 * already been scheduled. Already scheduled events can be processed
628 * by replacing the original head back.
629 * USING THIS FUNCTION CAN BE DANGEROUS TO THE HEALTH OF THE SIMULATOR.
630 * NOT RECOMMENDED FOR USE.
631 */
632 Event* replaceHead(Event* s);
633
634 /**@{*/
635 /**
636 * Provide an interface for locking/unlocking the event queue.
637 *
638 * @warn Do NOT use these methods directly unless you really know
639 * what you are doing. Incorrect use can easily lead to simulator
640 * deadlocks.
641 *
642 * @see EventQueue::ScopedMigration.
643 * @see EventQueue::ScopedRelease
644 * @see EventQueue
645 */
646 void lock() { service_mutex.lock(); }
647 void unlock() { service_mutex.unlock(); }
648 /**@}*/
649
650 /**
651 * Reschedule an event after a checkpoint.
652 *
653 * Since events don't know which event queue they belong to,
654 * parent objects need to reschedule events themselves. This
655 * method conditionally schedules an event that has the Scheduled
656 * flag set. It should be called by parent objects after
657 * unserializing an object.
658 *
659 * @warn Only use this method after unserializing an Event.
660 */
661 void checkpointReschedule(Event *event);
662
663 virtual ~EventQueue() { }
664};
665
666void dumpMainQueue();
667
668#ifndef SWIG
669class EventManager
670{
671 protected:
672 /** A pointer to this object's event queue */
673 EventQueue *eventq;
674
675 public:
676 EventManager(EventManager &em) : eventq(em.eventq) {}
677 EventManager(EventManager *em) : eventq(em->eventq) {}
678 EventManager(EventQueue *eq) : eventq(eq) {}
679
680 EventQueue *
681 eventQueue() const
682 {
683 return eventq;
684 }
685
686 void
687 schedule(Event &event, Tick when)
688 {
689 eventq->schedule(&event, when);
690 }
691
692 void
693 deschedule(Event &event)
694 {
695 eventq->deschedule(&event);
696 }
697
698 void
699 reschedule(Event &event, Tick when, bool always = false)
700 {
701 eventq->reschedule(&event, when, always);
702 }
703
704 void
705 schedule(Event *event, Tick when)
706 {
707 eventq->schedule(event, when);
708 }
709
710 void
711 deschedule(Event *event)
712 {
713 eventq->deschedule(event);
714 }
715
716 void
717 reschedule(Event *event, Tick when, bool always = false)
718 {
719 eventq->reschedule(event, when, always);
720 }
721
722 void wakeupEventQueue(Tick when = (Tick)-1)
723 {
724 eventq->wakeup(when);
725 }
726
727 void setCurTick(Tick newVal) { eventq->setCurTick(newVal); }
728};
729
730template <class T, void (T::* F)()>
731void
732DelayFunction(EventQueue *eventq, Tick when, T *object)
733{
734 class DelayEvent : public Event
735 {
736 private:
737 T *object;
738
739 public:
740 DelayEvent(T *o)
741 : Event(Default_Pri, AutoDelete), object(o)
742 { }
743 void process() { (object->*F)(); }
744 const char *description() const { return "delay"; }
745 };
746
747 eventq->schedule(new DelayEvent(object), when);
748}
749
750template <class T, void (T::* F)()>
751class EventWrapper : public Event
752{
753 private:
754 T *object;
755
756 public:
757 EventWrapper(T *obj, bool del = false, Priority p = Default_Pri)
758 : Event(p), object(obj)
759 {
760 if (del)
761 setFlags(AutoDelete);
762 }
763
764 EventWrapper(T &obj, bool del = false, Priority p = Default_Pri)
765 : Event(p), object(&obj)
766 {
767 if (del)
768 setFlags(AutoDelete);
769 }
770
771 void process() { (object->*F)(); }
772
773 const std::string
774 name() const
775 {
776 return object->name() + ".wrapped_event";
777 }
778
779 const char *description() const { return "EventWrapped"; }
780};
781#endif
782
783#endif // __SIM_EVENTQ_HH__