scheduler.cc revision 13063:c9905ead0041 
1/*
2 * Copyright 2018 Google, Inc.
3 *
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5 * modification, are permitted provided that the following conditions are
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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), _current(nullptr), initReady(false),
50    runOnce(false)
51{}
52
53void
54Scheduler::prepareForInit()
55{
56    for (Process *p = toFinalize.getNext(); p; p = toFinalize.getNext()) {
57        p->finalize();
58        p->popListNode();
59    }
60
61    for (Process *p = initList.getNext(); p; p = initList.getNext()) {
62        p->finalize();
63        p->popListNode();
64        p->ready();
65    }
66
67    for (auto ets: eventsToSchedule)
68        eq->schedule(ets.first, ets.second);
69    eventsToSchedule.clear();
70
71    if (_started)
72        eq->schedule(&maxTickEvent, maxTick);
73
74    initReady = true;
75}
76
77void
78Scheduler::reg(Process *p)
79{
80    if (initReady) {
81        // If we're past initialization, finalize static sensitivity.
82        p->finalize();
83        // Mark the process as ready.
84        p->ready();
85    } else {
86        // Otherwise, record that this process should be initialized once we
87        // get there.
88        initList.pushLast(p);
89    }
90}
91
92void
93Scheduler::dontInitialize(Process *p)
94{
95    if (initReady) {
96        // Pop this process off of the ready list.
97        p->popListNode();
98    } else {
99        // Push this process onto the list of processes which still need
100        // their static sensitivity to be finalized. That implicitly pops it
101        // off the list of processes to be initialized/marked ready.
102        toFinalize.pushLast(p);
103    }
104}
105
106void
107Scheduler::yield()
108{
109    _current = readyList.getNext();
110    if (!_current) {
111        // There are no more processes, so return control to evaluate.
112        Fiber::primaryFiber()->run();
113    } else {
114        _current->popListNode();
115        // Switch to whatever Fiber is supposed to run this process. All
116        // Fibers which aren't running should be parked at this line.
117        _current->fiber()->run();
118        // If the current process needs to be manually started, start it.
119        if (_current && _current->needsStart())
120            _current->run();
121    }
122    if (_current && _current->excWrapper) {
123        // Make sure this isn't a method process.
124        assert(!_current->needsStart());
125        auto ew = _current->excWrapper;
126        _current->excWrapper = nullptr;
127        ew->throw_it();
128    }
129}
130
131void
132Scheduler::ready(Process *p)
133{
134    // Clump methods together to minimize context switching.
135    if (p->procKind() == ::sc_core::SC_METHOD_PROC_)
136        readyList.pushFirst(p);
137    else
138        readyList.pushLast(p);
139
140    scheduleReadyEvent();
141}
142
143void
144Scheduler::requestUpdate(Channel *c)
145{
146    updateList.pushLast(c);
147    if (eq)
148        scheduleReadyEvent();
149}
150
151void
152Scheduler::scheduleReadyEvent()
153{
154    // Schedule the evaluate and update phases.
155    if (!readyEvent.scheduled()) {
156        panic_if(!eq, "Need to schedule ready, but no event manager.\n");
157        eq->schedule(&readyEvent, eq->getCurTick());
158        if (starvationEvent.scheduled())
159            eq->deschedule(&starvationEvent);
160    }
161}
162
163void
164Scheduler::scheduleStarvationEvent()
165{
166    if (!starvationEvent.scheduled()) {
167        panic_if(!eq, "Need to schedule starvation event, "
168                "but no event manager.\n");
169        eq->schedule(&starvationEvent, eq->getCurTick());
170        if (readyEvent.scheduled())
171            eq->deschedule(&readyEvent);
172    }
173}
174
175void
176Scheduler::runReady()
177{
178    bool empty = readyList.empty();
179
180    // The evaluation phase.
181    do {
182        yield();
183    } while (!readyList.empty());
184
185    if (!empty)
186        _numCycles++;
187
188    // The update phase.
189    update();
190
191    if (starved() && !runToTime)
192        scheduleStarvationEvent();
193
194    // The delta phase.
195    for (auto &e: deltas)
196        e->run();
197    deltas.clear();
198
199    if (runOnce) {
200        eq->reschedule(&maxTickEvent, eq->getCurTick());
201        runOnce = false;
202    }
203}
204
205void
206Scheduler::update()
207{
208    Channel *channel = updateList.getNext();
209    while (channel) {
210        channel->popListNode();
211        channel->update();
212        channel = updateList.getNext();
213    }
214}
215
216void
217Scheduler::pause()
218{
219    _paused = true;
220    kernel->status(::sc_core::SC_PAUSED);
221    runOnce = false;
222    scMain->run();
223
224    // If the ready event is supposed to run now, run it inline so that it
225    // preempts any delta notifications which were scheduled while we were
226    // paused.
227    if (readyEvent.scheduled()) {
228        eq->deschedule(&readyEvent);
229        runReady();
230    }
231}
232
233void
234Scheduler::stop()
235{
236    _stopped = true;
237    kernel->stop();
238    runOnce = false;
239    scMain->run();
240}
241
242void
243Scheduler::start(Tick max_tick, bool run_to_time)
244{
245    // We should be running from sc_main. Keep track of that Fiber to return
246    // to later.
247    scMain = Fiber::currentFiber();
248
249    _started = true;
250    _paused = false;
251    _stopped = false;
252    runToTime = run_to_time;
253
254    maxTick = max_tick;
255
256    if (starved() && !runToTime)
257        return;
258
259    if (initReady) {
260        kernel->status(::sc_core::SC_RUNNING);
261        eq->schedule(&maxTickEvent, maxTick);
262    }
263
264    // Return to gem5 to let it run events, etc.
265    Fiber::primaryFiber()->run();
266
267    if (pauseEvent.scheduled())
268        eq->deschedule(&pauseEvent);
269    if (stopEvent.scheduled())
270        eq->deschedule(&stopEvent);
271    if (maxTickEvent.scheduled())
272        eq->deschedule(&maxTickEvent);
273    if (starvationEvent.scheduled())
274        eq->deschedule(&starvationEvent);
275}
276
277void
278Scheduler::oneCycle()
279{
280    runOnce = true;
281    start(::MaxTick, false);
282}
283
284void
285Scheduler::schedulePause()
286{
287    if (pauseEvent.scheduled())
288        return;
289
290    eq->schedule(&pauseEvent, eq->getCurTick());
291}
292
293void
294Scheduler::scheduleStop(bool finish_delta)
295{
296    if (stopEvent.scheduled())
297        return;
298
299    if (!finish_delta) {
300        // If we're not supposed to finish the delta cycle, flush the list
301        // of ready processes and scheduled updates.
302        Process *p;
303        while ((p = readyList.getNext()))
304            p->popListNode();
305        Channel *c;
306        while ((c = updateList.getNext()))
307            c->popListNode();
308    }
309    eq->schedule(&stopEvent, eq->getCurTick());
310}
311
312Scheduler scheduler;
313
314} // namespace sc_gem5
315