scheduler.cc revision 13176:76f52e8d8c6a 
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
418