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
111 for (Process *p = initList.getNext(); p; p = initList.getNext()) {
112 p->finalize();
113 p->popListNode();
114 p->ready();
115 }
116
117 update();
118
119 while (!deltas.empty())
120 deltas.front()->run();
121
122 for (auto ets: eventsToSchedule)
123 eq->schedule(ets.first, ets.second);
124 eventsToSchedule.clear();
125
126 if (_started) {
127 if (!runToTime && starved())
128 scheduleStarvationEvent();
129 kernel->status(::sc_core::SC_RUNNING);
130 }
131
132 initDone = true;
133}
134
135void
136Scheduler::reg(Process *p)
137{
138 if (initDone) {
139 // If we're past initialization, finalize static sensitivity.
140 p->finalize();
141 // Mark the process as ready.
142 p->ready();
143 } else {
144 // Otherwise, record that this process should be initialized once we
145 // get there.
146 initList.pushLast(p);
147 }
148}
149
150void
151Scheduler::dontInitialize(Process *p)
152{
153 if (initDone) {
154 // Pop this process off of the ready list.
155 p->popListNode();
156 } else {
157 // Push this process onto the list of processes which still need
158 // their static sensitivity to be finalized. That implicitly pops it
159 // off the list of processes to be initialized/marked ready.
160 toFinalize.pushLast(p);
161 }
162}
163
164void
165Scheduler::yield()
166{
167 // Pull a process from the active list.
168 _current = readyList->getNext();
169 if (!_current) {
170 // There are no more processes, so return control to evaluate.
171 Fiber::primaryFiber()->run();
172 } else {
173 _current->popListNode();
174 // Switch to whatever Fiber is supposed to run this process. All
175 // Fibers which aren't running should be parked at this line.
176 _current->fiber()->run();
177 // If the current process needs to be manually started, start it.
178 if (_current && _current->needsStart()) {
179 _current->needsStart(false);
180 _current->run();
181 }
182 }
183 if (_current && _current->excWrapper) {
184 // Make sure this isn't a method process.
185 assert(!_current->needsStart());
186 auto ew = _current->excWrapper;
187 _current->excWrapper = nullptr;
188 ew->throw_it();
189 }
190}
191
192void
193Scheduler::ready(Process *p)
194{
195 if (_stopNow)
196 return;
197
198 if (p->procKind() == ::sc_core::SC_METHOD_PROC_)
199 readyListMethods.pushLast(p);
200 else
201 readyListThreads.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
216listContains(ListNode *list, ListNode *target)
217{
218 ListNode *n = list->nextListNode;
219 while (n != list)
220 if (n == target)
221 return true;
222 return false;
223}
224
225bool
226Scheduler::suspend(Process *p)
227{
228 bool was_ready;
229 if (initDone) {
230 // After initialization, the only list we can be on is the ready list.
231 was_ready = (p->nextListNode != nullptr);
232 p->popListNode();
233 } else {
234 // Check the ready lists to see if we find this process.
235 was_ready = listContains(&readyListMethods, p) ||
236 listContains(&readyListThreads, p);
237 if (was_ready)
238 toFinalize.pushLast(p);
239 }
240 return was_ready;
241}
242
243void
244Scheduler::requestUpdate(Channel *c)
245{
246 updateList.pushLast(c);
247 scheduleReadyEvent();
248}
249
250void
251Scheduler::scheduleReadyEvent()
252{
253 // Schedule the evaluate and update phases.
254 if (!readyEvent.scheduled()) {
255 schedule(&readyEvent);
256 if (starvationEvent.scheduled())
257 deschedule(&starvationEvent);
258 }
259}
260
261void
262Scheduler::scheduleStarvationEvent()
263{
264 if (!starvationEvent.scheduled()) {
265 schedule(&starvationEvent);
266 if (readyEvent.scheduled())
267 deschedule(&readyEvent);
268 }
269}
270
271void
272Scheduler::runReady()
273{
274 bool empty = readyListMethods.empty() && readyListThreads.empty();
275 lastReadyTick = getCurTick();
276
277 // The evaluation phase.
278 do {
279 // We run methods and threads in two seperate passes to emulate how
280 // Accellera orders things, but without having to scan through a
281 // unified list to find the next process of the correct type.
282 readyList = &readyListMethods;
283 while (!readyListMethods.empty())
284 yield();
285
286 readyList = &readyListThreads;
287 while (!readyListThreads.empty())
288 yield();
289
290 // We already know that readyListThreads is empty at this point.
291 } while (!readyListMethods.empty());
292
293 if (!empty) {
294 _numCycles++;
295 _changeStamp++;
296 }
297
298 if (_stopNow)
299 return;
300
301 // The update phase.
302 update();
303
304 // The delta phase.
305 while (!deltas.empty())
306 deltas.front()->run();
307
308 if (!runToTime && starved())
309 scheduleStarvationEvent();
310
311 if (runOnce)
312 schedulePause();
313}
314
315void
316Scheduler::update()
317{
318 Channel *channel = updateList.getNext();
319 while (channel) {
320 channel->popListNode();
321 channel->update();
322 channel = updateList.getNext();
323 }
324}
325
326void
327Scheduler::pause()
328{
329 _paused = true;
330 kernel->status(::sc_core::SC_PAUSED);
331 runOnce = false;
332 scMain->run();
333}
334
335void
336Scheduler::stop()
337{
338 _stopped = true;
339 kernel->stop();
340
341 clear();
342
343 runOnce = false;
344 scMain->run();
345}
346
347void
348Scheduler::start(Tick max_tick, bool run_to_time)
349{
350 // We should be running from sc_main. Keep track of that Fiber to return
351 // to later.
352 scMain = Fiber::currentFiber();
353
354 _started = true;
355 _paused = false;
356 _stopped = false;
357 runToTime = run_to_time;
358
359 maxTick = max_tick;
360 lastReadyTick = getCurTick();
361
362 if (initDone) {
363 if (!runToTime && starved())
364 scheduleStarvationEvent();
365 kernel->status(::sc_core::SC_RUNNING);
366 }
367
368 schedule(&maxTickEvent, maxTick);
369
370 // Return to gem5 to let it run events, etc.
371 Fiber::primaryFiber()->run();
372
373 if (pauseEvent.scheduled())
374 deschedule(&pauseEvent);
375 if (stopEvent.scheduled())
376 deschedule(&stopEvent);
377 if (maxTickEvent.scheduled())
378 deschedule(&maxTickEvent);
379 if (starvationEvent.scheduled())
380 deschedule(&starvationEvent);
381}
382
383void
384Scheduler::oneCycle()
385{
386 runOnce = true;
387 scheduleReadyEvent();
388 start(::MaxTick, false);
389}
390
391void
392Scheduler::schedulePause()
393{
394 if (pauseEvent.scheduled())
395 return;
396
397 schedule(&pauseEvent);
398}
399
400void
401Scheduler::scheduleStop(bool finish_delta)
402{
403 if (stopEvent.scheduled())
404 return;
405
406 if (!finish_delta) {
407 _stopNow = true;
408 // If we're not supposed to finish the delta cycle, flush all
409 // pending activity.
410 clear();
411 }
412 schedule(&stopEvent);
413}
414
415Scheduler scheduler;
416
417} // namespace sc_gem5