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 <mutex>
46#include <string>
47
48#include "base/flags.hh"
49#include "base/misc.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 static const FlagsType AutoSerialize = 0x0008; // must be serialized
107 static const FlagsType IsExitEvent = 0x0010; // special exit event
108 static const FlagsType IsMainQueue = 0x0020; // on main event queue
109 static const FlagsType Initialized = 0x7a40; // somewhat random bits
110 static const FlagsType InitMask = 0xffc0; // mask for init bits
111
112 public:
113 typedef int8_t Priority;
114
115 /// Event priorities, to provide tie-breakers for events scheduled
116 /// at the same cycle. Most events are scheduled at the default
117 /// priority; these values are used to control events that need to
118 /// be ordered within a cycle.
119
120 /// Minimum priority
121 static const Priority Minimum_Pri = SCHAR_MIN;
122
123 /// If we enable tracing on a particular cycle, do that as the
124 /// very first thing so we don't miss any of the events on
125 /// that cycle (even if we enter the debugger).
126 static const Priority Debug_Enable_Pri = -101;
127
128 /// Breakpoints should happen before anything else (except
129 /// enabling trace output), so we don't miss any action when
130 /// debugging.
131 static const Priority Debug_Break_Pri = -100;
132
133 /// CPU switches schedule the new CPU's tick event for the
134 /// same cycle (after unscheduling the old CPU's tick event).
135 /// The switch needs to come before any tick events to make
136 /// sure we don't tick both CPUs in the same cycle.
137 static const Priority CPU_Switch_Pri = -31;
138
139 /// For some reason "delayed" inter-cluster writebacks are
140 /// scheduled before regular writebacks (which have default
141 /// priority). Steve?
142 static const Priority Delayed_Writeback_Pri = -1;
143
144 /// Default is zero for historical reasons.
145 static const Priority Default_Pri = 0;
146
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151 /// Serailization needs to occur before tick events also, so
152 /// that a serialize/unserialize is identical to an on-line
153 /// CPU switch.
154 static const Priority Serialize_Pri = 32;
155
156 /// CPU ticks must come after other associated CPU events
157 /// (such as writebacks).
158 static const Priority CPU_Tick_Pri = 50;
159
160 /// Statistics events (dump, reset, etc.) come after
161 /// everything else, but before exit.
162 static const Priority Stat_Event_Pri = 90;
163
164 /// Progress events come at the end.
165 static const Priority Progress_Event_Pri = 95;
166
167 /// If we want to exit on this cycle, it's the very last thing
168 /// we do.
169 static const Priority Sim_Exit_Pri = 100;
170
171 /// Maximum priority
172 static const Priority Maximum_Pri = SCHAR_MAX;
173};
174
175/*
176 * An item on an event queue. The action caused by a given
177 * event is specified by deriving a subclass and overriding the
178 * process() member function.
179 *
180 * Caution, the order of members is chosen to maximize data packing.
181 */
182class Event : public EventBase, public Serializable
183{
184 friend class EventQueue;
185
186 private:
187 // The event queue is now a linked list of linked lists. The
188 // 'nextBin' pointer is to find the bin, where a bin is defined as
189 // when+priority. All events in the same bin will be stored in a
190 // second linked list (a stack) maintained by the 'nextInBin'
191 // pointer. The list will be accessed in LIFO order. The end
192 // result is that the insert/removal in 'nextBin' is
193 // linear/constant, and the lookup/removal in 'nextInBin' is
194 // constant/constant. Hopefully this is a significant improvement
195 // over the current fully linear insertion.
196 Event *nextBin;
197 Event *nextInBin;
198
199 static Event *insertBefore(Event *event, Event *curr);
200 static Event *removeItem(Event *event, Event *last);
201
202 Tick _when; //!< timestamp when event should be processed
203 Priority _priority; //!< event priority
204 Flags flags;
205
206#ifndef NDEBUG
207 /// Global counter to generate unique IDs for Event instances
208 static Counter instanceCounter;
209
210 /// This event's unique ID. We can also use pointer values for
211 /// this but they're not consistent across runs making debugging
212 /// more difficult. Thus we use a global counter value when
213 /// debugging.
214 Counter instance;
215
216 /// queue to which this event belongs (though it may or may not be
217 /// scheduled on this queue yet)
218 EventQueue *queue;
219#endif
220
221#ifdef EVENTQ_DEBUG
222 Tick whenCreated; //!< time created
223 Tick whenScheduled; //!< time scheduled
224#endif
225
226 void
227 setWhen(Tick when, EventQueue *q)
228 {
229 _when = when;
230#ifndef NDEBUG
231 queue = q;
232#endif
233#ifdef EVENTQ_DEBUG
234 whenScheduled = curTick();
235#endif
236 }
237
238 bool
239 initialized() const
240 {
241 return this && (flags & InitMask) == Initialized;
242 }
243
244 protected:
245 /// Accessor for flags.
246 Flags
247 getFlags() const
248 {
249 return flags & PublicRead;
250 }
251
252 bool
253 isFlagSet(Flags _flags) const
254 {
255 assert(_flags.noneSet(~PublicRead));
256 return flags.isSet(_flags);
257 }
258
259 /// Accessor for flags.
260 void
261 setFlags(Flags _flags)
262 {
263 assert(_flags.noneSet(~PublicWrite));
264 flags.set(_flags);
265 }
266
267 void
268 clearFlags(Flags _flags)
269 {
270 assert(_flags.noneSet(~PublicWrite));
271 flags.clear(_flags);
272 }
273
274 void
275 clearFlags()
276 {
277 flags.clear(PublicWrite);
278 }
279
280 // This function isn't really useful if TRACING_ON is not defined
281 virtual void trace(const char *action); //!< trace event activity
282
283 public:
284
285 /*
286 * Event constructor
287 * @param queue that the event gets scheduled on
288 */
289 Event(Priority p = Default_Pri, Flags f = 0)
290 : nextBin(NULL), nextInBin(NULL), _priority(p),
291 flags(Initialized | f)
292 {
293 assert(f.noneSet(~PublicWrite));
294#ifndef NDEBUG
295 instance = ++instanceCounter;
296 queue = NULL;
297#endif
298#ifdef EVENTQ_DEBUG
299 whenCreated = curTick();
300 whenScheduled = 0;
301#endif
302 }
303
304 virtual ~Event();
305 virtual const std::string name() const;
306
307 /// Return a C string describing the event. This string should
308 /// *not* be dynamically allocated; just a const char array
309 /// describing the event class.
310 virtual const char *description() const;
311
312 /// Dump the current event data
313 void dump() const;
314
315 public:
316 /*
317 * This member function is invoked when the event is processed
318 * (occurs). There is no default implementation; each subclass
319 * must provide its own implementation. The event is not
320 * automatically deleted after it is processed (to allow for
321 * statically allocated event objects).
322 *
323 * If the AutoDestroy flag is set, the object is deleted once it
324 * is processed.
325 */
326 virtual void process() = 0;
327
328 /// Determine if the current event is scheduled
329 bool scheduled() const { return flags.isSet(Scheduled); }
330
331 /// Squash the current event
332 void squash() { flags.set(Squashed); }
333
334 /// Check whether the event is squashed
335 bool squashed() const { return flags.isSet(Squashed); }
336
337 /// See if this is a SimExitEvent (without resorting to RTTI)
338 bool isExitEvent() const { return flags.isSet(IsExitEvent); }
339
340 /// Get the time that the event is scheduled
341 Tick when() const { return _when; }
342
343 /// Get the event priority
344 Priority priority() const { return _priority; }
345
346 //! If this is part of a GlobalEvent, return the pointer to the
347 //! Global Event. By default, there is no GlobalEvent, so return
348 //! NULL. (Overridden in GlobalEvent::BarrierEvent.)
349 virtual BaseGlobalEvent *globalEvent() { return NULL; }
350
351#ifndef SWIG
352 virtual void serialize(std::ostream &os);
353 virtual void unserialize(Checkpoint *cp, const std::string §ion);
354
355 //! This function is required to support restoring from checkpoints
356 //! when running with multiple queues. Since we still have not thrashed
357 //! out all the details on checkpointing, this function is most likely
358 //! to be revisited in future.
359 virtual void unserialize(Checkpoint *cp, const std::string §ion,
360 EventQueue *eventq);
361#endif
362};
363
364#ifndef SWIG
365inline bool
366operator<(const Event &l, const Event &r)
367{
368 return l.when() < r.when() ||
369 (l.when() == r.when() && l.priority() < r.priority());
370}
371
372inline bool
373operator>(const Event &l, const Event &r)
374{
375 return l.when() > r.when() ||
376 (l.when() == r.when() && l.priority() > r.priority());
377}
378
379inline bool
380operator<=(const Event &l, const Event &r)
381{
382 return l.when() < r.when() ||
383 (l.when() == r.when() && l.priority() <= r.priority());
384}
385inline bool
386operator>=(const Event &l, const Event &r)
387{
388 return l.when() > r.when() ||
389 (l.when() == r.when() && l.priority() >= r.priority());
390}
391
392inline bool
393operator==(const Event &l, const Event &r)
394{
395 return l.when() == r.when() && l.priority() == r.priority();
396}
397
398inline bool
399operator!=(const Event &l, const Event &r)
400{
401 return l.when() != r.when() || l.priority() != r.priority();
402}
403#endif
404
405/**
406 * Queue of events sorted in time order
407 *
408 * Events are scheduled (inserted into the event queue) using the
409 * schedule() method. This method either inserts a <i>synchronous</i>
410 * or <i>asynchronous</i> event.
411 *
412 * Synchronous events are scheduled using schedule() method with the
413 * argument 'global' set to false (default). This should only be done
414 * from a thread holding the event queue lock
415 * (EventQueue::service_mutex). The lock is always held when an event
416 * handler is called, it can therefore always insert events into its
417 * own event queue unless it voluntarily releases the lock.
418 *
419 * Events can be scheduled across thread (and event queue borders) by
420 * either scheduling asynchronous events or taking the target event
421 * queue's lock. However, the lock should <i>never</i> be taken
422 * directly since this is likely to cause deadlocks. Instead, code
423 * that needs to schedule events in other event queues should
424 * temporarily release its own queue and lock the new queue. This
425 * prevents deadlocks since a single thread never owns more than one
426 * event queue lock. This functionality is provided by the
427 * ScopedMigration helper class. Note that temporarily migrating
428 * between event queues can make the simulation non-deterministic, it
429 * should therefore be limited to cases where that can be tolerated
430 * (e.g., handling asynchronous IO or fast-forwarding in KVM).
431 *
432 * Asynchronous events can also be scheduled using the normal
433 * schedule() method with the 'global' parameter set to true. Unlike
434 * the previous queue migration strategy, this strategy is fully
435 * deterministic. This causes the event to be inserted in a separate
436 * queue of asynchronous events (async_queue), which is merged main
437 * event queue at the end of each simulation quantum (by calling the
438 * handleAsyncInsertions() method). Note that this implies that such
439 * events must happen at least one simulation quantum into the future,
440 * otherwise they risk being scheduled in the past by
441 * handleAsyncInsertions().
442 */
443class EventQueue : public Serializable
444{
445 private:
446 std::string objName;
447 Event *head;
448 Tick _curTick;
449
450 //! Mutex to protect async queue.
451 std::mutex *async_queue_mutex;
452
453 //! List of events added by other threads to this event queue.
454 std::list<Event*> async_queue;
455
456 /**
457 * Lock protecting event handling.
458 *
459 * This lock is always taken when servicing events. It is assumed
460 * that the thread scheduling new events (not asynchronous events
461 * though) have taken this lock. This is normally done by
462 * serviceOne() since new events are typically scheduled as a
463 * response to an earlier event.
464 *
465 * This lock is intended to be used to temporarily steal an event
466 * queue to support inter-thread communication when some
467 * deterministic timing can be sacrificed for speed. For example,
468 * the KVM CPU can use this support to access devices running in a
469 * different thread.
470 *
471 * @see EventQueue::ScopedMigration.
472 * @see EventQueue::ScopedRelease
473 * @see EventQueue::lock()
474 * @see EventQueue::unlock()
475 */
476 std::mutex service_mutex;
477
478 //! Insert / remove event from the queue. Should only be called
479 //! by thread operating this queue.
480 void insert(Event *event);
481 void remove(Event *event);
482
483 //! Function for adding events to the async queue. The added events
484 //! are added to main event queue later. Threads, other than the
485 //! owning thread, should call this function instead of insert().
486 void asyncInsert(Event *event);
487
488 EventQueue(const EventQueue &);
489
490 public:
491#ifndef SWIG
492 /**
493 * Temporarily migrate execution to a different event queue.
494 *
495 * An instance of this class temporarily migrates execution to a
496 * different event queue by releasing the current queue, locking
497 * the new queue, and updating curEventQueue(). This can, for
498 * example, be useful when performing IO across thread event
499 * queues when timing is not crucial (e.g., during fast
500 * forwarding).
501 */
502 class ScopedMigration
503 {
504 public:
505 ScopedMigration(EventQueue *_new_eq)
506 : new_eq(*_new_eq), old_eq(*curEventQueue())
507 {
508 old_eq.unlock();
509 new_eq.lock();
510 curEventQueue(&new_eq);
511 }
512
513 ~ScopedMigration()
514 {
515 new_eq.unlock();
516 old_eq.lock();
517 curEventQueue(&old_eq);
518 }
519
520 private:
521 EventQueue &new_eq;
522 EventQueue &old_eq;
523 };
524
525 /**
526 * Temporarily release the event queue service lock.
527 *
528 * There are cases where it is desirable to temporarily release
529 * the event queue lock to prevent deadlocks. For example, when
530 * waiting on the global barrier, we need to release the lock to
531 * prevent deadlocks from happening when another thread tries to
532 * temporarily take over the event queue waiting on the barrier.
533 */
534 class ScopedRelease
535 {
536 public:
537 ScopedRelease(EventQueue *_eq)
538 : eq(*_eq)
539 {
540 eq.unlock();
541 }
542
543 ~ScopedRelease()
544 {
545 eq.lock();
546 }
547
548 private:
549 EventQueue &eq;
550 };
551#endif
552
553 EventQueue(const std::string &n);
554
555 virtual const std::string name() const { return objName; }
556 void name(const std::string &st) { objName = st; }
557
558 //! Schedule the given event on this queue. Safe to call from any
559 //! thread.
560 void schedule(Event *event, Tick when, bool global = false);
561
562 //! Deschedule the specified event. Should be called only from the
563 //! owning thread.
564 void deschedule(Event *event);
565
566 //! Reschedule the specified event. Should be called only from
567 //! the owning thread.
568 void reschedule(Event *event, Tick when, bool always = false);
569
570 Tick nextTick() const { return head->when(); }
571 void setCurTick(Tick newVal) { _curTick = newVal; }
572 Tick getCurTick() { return _curTick; }
573
574 Event *serviceOne();
575
576 // process all events up to the given timestamp. we inline a
577 // quick test to see if there are any events to process; if so,
578 // call the internal out-of-line version to process them all.
579 void
580 serviceEvents(Tick when)
581 {
582 while (!empty()) {
583 if (nextTick() > when)
584 break;
585
586 /**
587 * @todo this assert is a good bug catcher. I need to
588 * make it true again.
589 */
590 //assert(head->when() >= when && "event scheduled in the past");
591 serviceOne();
592 }
593
594 setCurTick(when);
595 }
596
597 // return true if no events are queued
598 bool empty() const { return head == NULL; }
599
600 void dump() const;
601
602 bool debugVerify() const;
603
604 //! Function for moving events from the async_queue to the main queue.
605 void handleAsyncInsertions();
606
607 /**
608 * function for replacing the head of the event queue, so that a
609 * different set of events can run without disturbing events that have
610 * already been scheduled. Already scheduled events can be processed
611 * by replacing the original head back.
612 * USING THIS FUNCTION CAN BE DANGEROUS TO THE HEALTH OF THE SIMULATOR.
613 * NOT RECOMMENDED FOR USE.
614 */
615 Event* replaceHead(Event* s);
616
617 /**@{*/
618 /**
619 * Provide an interface for locking/unlocking the event queue.
620 *
621 * @warn Do NOT use these methods directly unless you really know
622 * what you are doing. Incorrect use can easily lead to simulator
623 * deadlocks.
624 *
625 * @see EventQueue::ScopedMigration.
626 * @see EventQueue::ScopedRelease
627 * @see EventQueue
628 */
629 void lock() { service_mutex.lock(); }
630 void unlock() { service_mutex.unlock(); }
631 /**@}*/
632
633#ifndef SWIG
634 virtual void serialize(std::ostream &os);
635 virtual void unserialize(Checkpoint *cp, const std::string §ion);
636#endif
637};
638
639void dumpMainQueue();
640
641#ifndef SWIG
642class EventManager
643{
644 protected:
645 /** A pointer to this object's event queue */
646 EventQueue *eventq;
647
648 public:
649 EventManager(EventManager &em) : eventq(em.eventq) {}
650 EventManager(EventManager *em) : eventq(em->eventq) {}
651 EventManager(EventQueue *eq) : eventq(eq) {}
652
653 EventQueue *
654 eventQueue() const
655 {
656 return eventq;
657 }
658
659 void
660 schedule(Event &event, Tick when)
661 {
662 eventq->schedule(&event, when);
663 }
664
665 void
666 deschedule(Event &event)
667 {
668 eventq->deschedule(&event);
669 }
670
671 void
672 reschedule(Event &event, Tick when, bool always = false)
673 {
674 eventq->reschedule(&event, when, always);
675 }
676
677 void
678 schedule(Event *event, Tick when)
679 {
680 eventq->schedule(event, when);
681 }
682
683 void
684 deschedule(Event *event)
685 {
686 eventq->deschedule(event);
687 }
688
689 void
690 reschedule(Event *event, Tick when, bool always = false)
691 {
692 eventq->reschedule(event, when, always);
693 }
694
695 void setCurTick(Tick newVal) { eventq->setCurTick(newVal); }
696};
697
698template <class T, void (T::* F)()>
699void
700DelayFunction(EventQueue *eventq, Tick when, T *object)
701{
702 class DelayEvent : public Event
703 {
704 private:
705 T *object;
706
707 public:
708 DelayEvent(T *o)
709 : Event(Default_Pri, AutoDelete), object(o)
710 { }
711 void process() { (object->*F)(); }
712 const char *description() const { return "delay"; }
713 };
714
715 eventq->schedule(new DelayEvent(object), when);
716}
717
718template <class T, void (T::* F)()>
719class EventWrapper : public Event
720{
721 private:
722 T *object;
723
724 public:
725 EventWrapper(T *obj, bool del = false, Priority p = Default_Pri)
726 : Event(p), object(obj)
727 {
728 if (del)
729 setFlags(AutoDelete);
730 }
731
732 EventWrapper(T &obj, bool del = false, Priority p = Default_Pri)
733 : Event(p), object(&obj)
734 {
735 if (del)
736 setFlags(AutoDelete);
737 }
738
739 void process() { (object->*F)(); }
740
741 const std::string
742 name() const
743 {
744 return object->name() + ".wrapped_event";
745 }
746
747 const char *description() const { return "EventWrapped"; }
748};
749#endif
750
751#endif // __SIM_EVENTQ_HH__
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