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),
48 maxTickEvent(this, false, MaxTickPriority),
49 _numCycles(0), _changeStamp(0), _current(nullptr), initDone(false),
50 runOnce(false)
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 = readyList.getNext()))
94 p->popListNode();
95
96 Channel *c;
97 while ((c = updateList.getNext()))
98 c->popListNode();
99}
100
101void
102Scheduler::initPhase()
103{
104 for (Process *p = toFinalize.getNext(); p; p = toFinalize.getNext()) {
105 p->finalize();
106 p->popListNode();
107 }
108
109 for (Process *p = initList.getNext(); p; p = initList.getNext()) {
110 p->finalize();
111 p->popListNode();
112 p->ready();
113 }
114
115 update();
116
117 while (!deltas.empty())
118 deltas.front()->run();
119
120 for (auto ets: eventsToSchedule)
121 eq->schedule(ets.first, ets.second);
122 eventsToSchedule.clear();
123
124 if (_started) {
125 if (!runToTime && starved())
126 scheduleStarvationEvent();
127 kernel->status(::sc_core::SC_RUNNING);
128 }
129
130 initDone = true;
131}
132
133void
134Scheduler::reg(Process *p)
135{
136 if (initDone) {
137 // If we're past initialization, finalize static sensitivity.
138 p->finalize();
139 // Mark the process as ready.
140 p->ready();
141 } else {
142 // Otherwise, record that this process should be initialized once we
143 // get there.
144 initList.pushLast(p);
145 }
146}
147
148void
149Scheduler::dontInitialize(Process *p)
150{
151 if (initDone) {
152 // Pop this process off of the ready list.
153 p->popListNode();
154 } else {
155 // Push this process onto the list of processes which still need
156 // their static sensitivity to be finalized. That implicitly pops it
157 // off the list of processes to be initialized/marked ready.
158 toFinalize.pushLast(p);
159 }
160}
161
162void
163Scheduler::yield()
164{
165 _current = readyList.getNext();
166 if (!_current) {
167 // There are no more processes, so return control to evaluate.
168 Fiber::primaryFiber()->run();
169 } else {
170 _current->popListNode();
171 // Switch to whatever Fiber is supposed to run this process. All
172 // Fibers which aren't running should be parked at this line.
173 _current->fiber()->run();
174 // If the current process needs to be manually started, start it.
175 if (_current && _current->needsStart()) {
176 _current->needsStart(false);
177 _current->run();
178 }
179 }
180 if (_current && _current->excWrapper) {
181 // Make sure this isn't a method process.
182 assert(!_current->needsStart());
183 auto ew = _current->excWrapper;
184 _current->excWrapper = nullptr;
185 ew->throw_it();
186 }
187}
188
189void
190Scheduler::ready(Process *p)
191{
192 // Clump methods together to minimize context switching.
193 static bool cluster_methods = false;
194
195 if (cluster_methods && p->procKind() == ::sc_core::SC_METHOD_PROC_)
196 readyList.pushFirst(p);
197 else
198 readyList.pushLast(p);
199
200 scheduleReadyEvent();
201}
202
203void
204Scheduler::resume(Process *p)
205{
206 if (initDone)
207 ready(p);
208 else
209 initList.pushLast(p);
210}
211
212bool
213Scheduler::suspend(Process *p)
214{
215 if (initDone) {
216 // After initialization, the only list we can be on is the ready list.
217 bool was_ready = (p->nextListNode != nullptr);
218 p->popListNode();
219 return was_ready;
220 } else {
221 bool was_ready = false;
222 // Check the ready list to see if we find this process.
223 ListNode *n = readyList.nextListNode;
224 while (n != &readyList) {
225 if (n == p) {
226 was_ready = true;
227 break;
228 }
229 }
230 if (was_ready)
231 toFinalize.pushLast(p);
232 return was_ready;
233 }
234}
235
236void
237Scheduler::requestUpdate(Channel *c)
238{
239 updateList.pushLast(c);
240 scheduleReadyEvent();
241}
242
243void
244Scheduler::scheduleReadyEvent()
245{
246 // Schedule the evaluate and update phases.
247 if (!readyEvent.scheduled()) {
248 schedule(&readyEvent);
249 if (starvationEvent.scheduled())
250 deschedule(&starvationEvent);
251 }
252}
253
254void
255Scheduler::scheduleStarvationEvent()
256{
257 if (!starvationEvent.scheduled()) {
258 schedule(&starvationEvent);
259 if (readyEvent.scheduled())
260 deschedule(&readyEvent);
261 }
262}
263
264void
265Scheduler::runReady()
266{
267 bool empty = readyList.empty();
268 lastReadyTick = getCurTick();
269
270 // The evaluation phase.
271 do {
272 yield();
273 } while (!readyList.empty());
274
275 if (!empty) {
276 _numCycles++;
277 _changeStamp++;
278 }
279
280 // The update phase.
281 update();
282
283 // The delta phase.
284 while (!deltas.empty())
285 deltas.front()->run();
286
287 if (!runToTime && starved())
288 scheduleStarvationEvent();
289
290 if (runOnce)
291 schedulePause();
292}
293
294void
295Scheduler::update()
296{
297 Channel *channel = updateList.getNext();
298 while (channel) {
299 channel->popListNode();
300 channel->update();
301 channel = updateList.getNext();
302 }
303}
304
305void
306Scheduler::pause()
307{
308 _paused = true;
309 kernel->status(::sc_core::SC_PAUSED);
310 runOnce = false;
311 scMain->run();
312}
313
314void
315Scheduler::stop()
316{
317 _stopped = true;
318 kernel->stop();
319
320 clear();
321
322 runOnce = false;
323 scMain->run();
324}
325
326void
327Scheduler::start(Tick max_tick, bool run_to_time)
328{
329 // We should be running from sc_main. Keep track of that Fiber to return
330 // to later.
331 scMain = Fiber::currentFiber();
332
333 _started = true;
334 _paused = false;
335 _stopped = false;
336 runToTime = run_to_time;
337
338 maxTick = max_tick;
339 lastReadyTick = getCurTick();
340
341 if (initDone) {
342 if (!runToTime && starved())
343 scheduleStarvationEvent();
344 kernel->status(::sc_core::SC_RUNNING);
345 }
346
347 schedule(&maxTickEvent, maxTick);
348
349 // Return to gem5 to let it run events, etc.
350 Fiber::primaryFiber()->run();
351
352 if (pauseEvent.scheduled())
353 deschedule(&pauseEvent);
354 if (stopEvent.scheduled())
355 deschedule(&stopEvent);
356 if (maxTickEvent.scheduled())
357 deschedule(&maxTickEvent);
358 if (starvationEvent.scheduled())
359 deschedule(&starvationEvent);
360}
361
362void
363Scheduler::oneCycle()
364{
365 runOnce = true;
366 scheduleReadyEvent();
367 start(::MaxTick, false);
368}
369
370void
371Scheduler::schedulePause()
372{
373 if (pauseEvent.scheduled())
374 return;
375
376 schedule(&pauseEvent);
377}
378
379void
380Scheduler::scheduleStop(bool finish_delta)
381{
382 if (stopEvent.scheduled())
383 return;
384
385 if (!finish_delta) {
386 // If we're not supposed to finish the delta cycle, flush all
387 // pending activity.
388 clear();
389 }
390 schedule(&stopEvent);
391}
392
393Scheduler scheduler;
394
395} // namespace sc_gem5