1/*
2 * Copyright 2018 Google, Inc.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions are
6 * met: redistributions of source code must retain the above copyright
7 * notice, this list of conditions and the following disclaimer;
8 * redistributions in binary form must reproduce the above copyright
9 * notice, this list of conditions and the following disclaimer in the
10 * documentation and/or other materials provided with the distribution;
11 * neither the name of the copyright holders nor the names of its
12 * contributors may be used to endorse or promote products derived from
13 * this software without specific prior written permission.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
18 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
19 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
20 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
21 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
25 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 *
27 * Authors: Gabe Black
28 */
29
30#include "systemc/core/scheduler.hh"
31
32#include "base/fiber.hh"
33#include "base/logging.hh"
34#include "sim/eventq.hh"
35#include "systemc/core/kernel.hh"
36#include "systemc/ext/core/sc_main.hh"
37
38namespace sc_gem5
39{
40
41Scheduler::Scheduler() :
42 eq(nullptr), readyEvent(this, false, ReadyPriority),
43 pauseEvent(this, false, PausePriority),
44 stopEvent(this, false, StopPriority),
45 scMain(nullptr),
46 starvationEvent(this, false, StarvationPriority),
47 _started(false), _paused(false), _stopped(false), _stopNow(false),
48 maxTickEvent(this, false, MaxTickPriority),
49 _numCycles(0), _changeStamp(0), _current(nullptr), initDone(false),
50 runOnce(false), readyList(nullptr)
51{}
52
53Scheduler::~Scheduler()
54{
55 // Clear out everything that belongs to us to make sure nobody tries to
56 // clear themselves out after the scheduler goes away.
57 clear();
58}
59
60void
61Scheduler::clear()
62{
63 // Delta notifications.
64 while (!deltas.empty())
65 deltas.front()->deschedule();
66
67 // Timed notifications.
68 for (auto &tsp: timeSlots) {
69 TimeSlot *&ts = tsp.second;
70 while (!ts->events.empty())
71 ts->events.front()->deschedule();
72 deschedule(ts);
73 }
74 timeSlots.clear();
75
76 // gem5 events.
77 if (readyEvent.scheduled())
78 deschedule(&readyEvent);
79 if (pauseEvent.scheduled())
80 deschedule(&pauseEvent);
81 if (stopEvent.scheduled())
82 deschedule(&stopEvent);
83 if (starvationEvent.scheduled())
84 deschedule(&starvationEvent);
85 if (maxTickEvent.scheduled())
86 deschedule(&maxTickEvent);
87
88 Process *p;
89 while ((p = toFinalize.getNext()))
90 p->popListNode();
91 while ((p = initList.getNext()))
92 p->popListNode();
93 while ((p = readyListMethods.getNext()))
94 p->popListNode();
95 while ((p = readyListThreads.getNext()))
96 p->popListNode();
97
98 Channel *c;
99 while ((c = updateList.getNext()))
100 c->popListNode();
101}
102
103void
104Scheduler::initPhase()
105{
106 for (Process *p = toFinalize.getNext(); p; p = toFinalize.getNext()) {
107 p->finalize();
108 p->popListNode();
109
110 if (!p->hasStaticSensitivities() && !p->internal()) {
111 SC_REPORT_WARNING(
112 "(W558) disable() or dont_initialize() called on process "
113 "with no static sensitivity, it will be orphaned",
114 p->name());
115 }
116 }
117
118 for (Process *p = initList.getNext(); p; p = initList.getNext()) {
119 p->finalize();
120 p->popListNode();
121 p->ready();
122 }
123
124 update();
125
126 while (!deltas.empty())
127 deltas.front()->run();
128
129 for (auto ets: eventsToSchedule)
130 eq->schedule(ets.first, ets.second);
131 eventsToSchedule.clear();
132
133 if (_started) {
134 if (!runToTime && starved())
135 scheduleStarvationEvent();
136 kernel->status(::sc_core::SC_RUNNING);
137 }
138
139 initDone = true;
140}
141
142void
143Scheduler::reg(Process *p)
144{
145 if (initDone) {
146 // If we're past initialization, finalize static sensitivity.
147 p->finalize();
148 // Mark the process as ready.
149 p->ready();
150 } else {
151 // Otherwise, record that this process should be initialized once we
152 // get there.
153 initList.pushLast(p);
154 }
155}
156
157void
158Scheduler::dontInitialize(Process *p)
159{
160 if (initDone) {
161 // Pop this process off of the ready list.
162 p->popListNode();
163 } else {
164 // Push this process onto the list of processes which still need
165 // their static sensitivity to be finalized. That implicitly pops it
166 // off the list of processes to be initialized/marked ready.
167 toFinalize.pushLast(p);
168 }
169}
170
171void
172Scheduler::yield()
173{
174 // Pull a process from the active list.
175 _current = readyList->getNext();
176 if (!_current) {
177 // There are no more processes, so return control to evaluate.
178 Fiber::primaryFiber()->run();
179 } else {
180 _current->popListNode();
181 // Switch to whatever Fiber is supposed to run this process. All
182 // Fibers which aren't running should be parked at this line.
183 _current->fiber()->run();
184 // If the current process needs to be manually started, start it.
185 if (_current && _current->needsStart()) {
186 _current->needsStart(false);
187 _current->run();
188 }
189 }
190 if (_current && _current->excWrapper) {
191 // Make sure this isn't a method process.
192 assert(!_current->needsStart());
193 auto ew = _current->excWrapper;
194 _current->excWrapper = nullptr;
195 ew->throw_it();
196 }
197}
198
199void
200Scheduler::ready(Process *p)
201{
202 if (_stopNow)
203 return;
204
205 if (p->procKind() == ::sc_core::SC_METHOD_PROC_)
206 readyListMethods.pushLast(p);
207 else
208 readyListThreads.pushLast(p);
209
210 scheduleReadyEvent();
211}
212
213void
214Scheduler::resume(Process *p)
215{
216 if (initDone)
217 ready(p);
218 else
219 initList.pushLast(p);
220}
221
222bool
223listContains(ListNode *list, ListNode *target)
224{
225 ListNode *n = list->nextListNode;
226 while (n != list)
227 if (n == target)
228 return true;
229 return false;
230}
231
232bool
233Scheduler::suspend(Process *p)
234{
235 bool was_ready;
236 if (initDone) {
237 // After initialization, the only list we can be on is the ready list.
238 was_ready = (p->nextListNode != nullptr);
239 p->popListNode();
240 } else {
241 // Check the ready lists to see if we find this process.
242 was_ready = listContains(&readyListMethods, p) ||
243 listContains(&readyListThreads, p);
244 if (was_ready)
245 toFinalize.pushLast(p);
246 }
247 return was_ready;
248}
249
250void
251Scheduler::requestUpdate(Channel *c)
252{
253 updateList.pushLast(c);
254 scheduleReadyEvent();
255}
256
257void
258Scheduler::scheduleReadyEvent()
259{
260 // Schedule the evaluate and update phases.
261 if (!readyEvent.scheduled()) {
262 schedule(&readyEvent);
263 if (starvationEvent.scheduled())
264 deschedule(&starvationEvent);
265 }
266}
267
268void
269Scheduler::scheduleStarvationEvent()
270{
271 if (!starvationEvent.scheduled()) {
272 schedule(&starvationEvent);
273 if (readyEvent.scheduled())
274 deschedule(&readyEvent);
275 }
276}
277
278void
279Scheduler::runReady()
280{
281 bool empty = readyListMethods.empty() && readyListThreads.empty();
282 lastReadyTick = getCurTick();
283
284 // The evaluation phase.
285 do {
286 // We run methods and threads in two seperate passes to emulate how
287 // Accellera orders things, but without having to scan through a
288 // unified list to find the next process of the correct type.
289 readyList = &readyListMethods;
290 while (!readyListMethods.empty())
291 yield();
292
293 readyList = &readyListThreads;
294 while (!readyListThreads.empty())
295 yield();
296
297 // We already know that readyListThreads is empty at this point.
298 } while (!readyListMethods.empty());
299
300 if (!empty) {
301 _numCycles++;
302 _changeStamp++;
303 }
304
305 if (_stopNow)
306 return;
307
308 // The update phase.
309 update();
310
311 // The delta phase.
312 while (!deltas.empty())
313 deltas.front()->run();
314
315 if (!runToTime && starved())
316 scheduleStarvationEvent();
317
318 if (runOnce)
319 schedulePause();
320}
321
322void
323Scheduler::update()
324{
325 Channel *channel = updateList.getNext();
326 while (channel) {
327 channel->popListNode();
328 channel->update();
329 channel = updateList.getNext();
330 }
331}
332
333void
334Scheduler::pause()
335{
336 _paused = true;
337 kernel->status(::sc_core::SC_PAUSED);
338 runOnce = false;
339 scMain->run();
340}
341
342void
343Scheduler::stop()
344{
345 _stopped = true;
346 kernel->stop();
347
348 clear();
349
350 runOnce = false;
351 scMain->run();
352}
353
354void
355Scheduler::start(Tick max_tick, bool run_to_time)
356{
357 // We should be running from sc_main. Keep track of that Fiber to return
358 // to later.
359 scMain = Fiber::currentFiber();
360
361 _started = true;
362 _paused = false;
363 _stopped = false;
364 runToTime = run_to_time;
365
366 maxTick = max_tick;
367 lastReadyTick = getCurTick();
368
369 if (initDone) {
370 if (!runToTime && starved())
371 scheduleStarvationEvent();
372 kernel->status(::sc_core::SC_RUNNING);
373 }
374
375 schedule(&maxTickEvent, maxTick);
376
377 // Return to gem5 to let it run events, etc.
378 Fiber::primaryFiber()->run();
379
380 if (pauseEvent.scheduled())
381 deschedule(&pauseEvent);
382 if (stopEvent.scheduled())
383 deschedule(&stopEvent);
384 if (maxTickEvent.scheduled())
385 deschedule(&maxTickEvent);
386 if (starvationEvent.scheduled())
387 deschedule(&starvationEvent);
388}
389
390void
391Scheduler::oneCycle()
392{
393 runOnce = true;
394 scheduleReadyEvent();
395 start(::MaxTick, false);
396}
397
398void
399Scheduler::schedulePause()
400{
401 if (pauseEvent.scheduled())
402 return;
403
404 schedule(&pauseEvent);
405}
406
407void
408Scheduler::scheduleStop(bool finish_delta)
409{
410 if (stopEvent.scheduled())
411 return;
412
413 if (!finish_delta) {
414 _stopNow = true;
415 // If we're not supposed to finish the delta cycle, flush all
416 // pending activity.
417 clear();
418 }
419 schedule(&stopEvent);
420}
421
422Scheduler scheduler;
423
424} // namespace sc_gem5