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)
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 if (_stopNow)
193 return;
194
195 // Clump methods together to minimize context switching.
196 static bool cluster_methods = false;
197
198 if (cluster_methods && p->procKind() == ::sc_core::SC_METHOD_PROC_)
199 readyList.pushFirst(p);
200 else
201 readyList.pushLast(p);
202
203 scheduleReadyEvent();
204}
205
206void
207Scheduler::resume(Process *p)
208{
209 if (initDone)
210 ready(p);
211 else
212 initList.pushLast(p);
213}
214
215bool
216Scheduler::suspend(Process *p)
217{
218 if (initDone) {
219 // After initialization, the only list we can be on is the ready list.
220 bool was_ready = (p->nextListNode != nullptr);
221 p->popListNode();
222 return was_ready;
223 } else {
224 bool was_ready = false;
225 // Check the ready list to see if we find this process.
226 ListNode *n = readyList.nextListNode;
227 while (n != &readyList) {
228 if (n == p) {
229 was_ready = true;
230 break;
231 }
232 }
233 if (was_ready)
234 toFinalize.pushLast(p);
235 return was_ready;
236 }
237}
238
239void
240Scheduler::requestUpdate(Channel *c)
241{
242 updateList.pushLast(c);
243 scheduleReadyEvent();
244}
245
246void
247Scheduler::scheduleReadyEvent()
248{
249 // Schedule the evaluate and update phases.
250 if (!readyEvent.scheduled()) {
251 schedule(&readyEvent);
252 if (starvationEvent.scheduled())
253 deschedule(&starvationEvent);
254 }
255}
256
257void
258Scheduler::scheduleStarvationEvent()
259{
260 if (!starvationEvent.scheduled()) {
261 schedule(&starvationEvent);
262 if (readyEvent.scheduled())
263 deschedule(&readyEvent);
264 }
265}
266
267void
268Scheduler::runReady()
269{
270 bool empty = readyList.empty();
271 lastReadyTick = getCurTick();
272
273 // The evaluation phase.
274 do {
275 yield();
276 } while (!readyList.empty());
277
278 if (!empty) {
279 _numCycles++;
280 _changeStamp++;
281 }
282
283 if (_stopNow)
284 return;
285
286 // The update phase.
287 update();
288
289 // The delta phase.
290 while (!deltas.empty())
291 deltas.front()->run();
292
293 if (!runToTime && starved())
294 scheduleStarvationEvent();
295
296 if (runOnce)
297 schedulePause();
298}
299
300void
301Scheduler::update()
302{
303 Channel *channel = updateList.getNext();
304 while (channel) {
305 channel->popListNode();
306 channel->update();
307 channel = updateList.getNext();
308 }
309}
310
311void
312Scheduler::pause()
313{
314 _paused = true;
315 kernel->status(::sc_core::SC_PAUSED);
316 runOnce = false;
317 scMain->run();
318}
319
320void
321Scheduler::stop()
322{
323 _stopped = true;
324 kernel->stop();
325
326 clear();
327
328 runOnce = false;
329 scMain->run();
330}
331
332void
333Scheduler::start(Tick max_tick, bool run_to_time)
334{
335 // We should be running from sc_main. Keep track of that Fiber to return
336 // to later.
337 scMain = Fiber::currentFiber();
338
339 _started = true;
340 _paused = false;
341 _stopped = false;
342 runToTime = run_to_time;
343
344 maxTick = max_tick;
345 lastReadyTick = getCurTick();
346
347 if (initDone) {
348 if (!runToTime && starved())
349 scheduleStarvationEvent();
350 kernel->status(::sc_core::SC_RUNNING);
351 }
352
353 schedule(&maxTickEvent, maxTick);
354
355 // Return to gem5 to let it run events, etc.
356 Fiber::primaryFiber()->run();
357
358 if (pauseEvent.scheduled())
359 deschedule(&pauseEvent);
360 if (stopEvent.scheduled())
361 deschedule(&stopEvent);
362 if (maxTickEvent.scheduled())
363 deschedule(&maxTickEvent);
364 if (starvationEvent.scheduled())
365 deschedule(&starvationEvent);
366}
367
368void
369Scheduler::oneCycle()
370{
371 runOnce = true;
372 scheduleReadyEvent();
373 start(::MaxTick, false);
374}
375
376void
377Scheduler::schedulePause()
378{
379 if (pauseEvent.scheduled())
380 return;
381
382 schedule(&pauseEvent);
383}
384
385void
386Scheduler::scheduleStop(bool finish_delta)
387{
388 if (stopEvent.scheduled())
389 return;
390
391 if (!finish_delta) {
392 _stopNow = true;
393 // If we're not supposed to finish the delta cycle, flush all
394 // pending activity.
395 clear();
396 }
397 schedule(&stopEvent);
398}
399
400Scheduler scheduler;
401
402} // namespace sc_gem5