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

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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
36namespace sc_gem5
37{
38
39Scheduler::Scheduler() :
40 eq(nullptr), readyEvent(this, false, EventBase::Default_Pri + 1),
41 _numCycles(0), _current(nullptr)
42{}
43
44void
45Scheduler::initToReady()
46{
47 while (!initList.empty())
48 ready(initList.getNext());
49}
50
51void
52Scheduler::yield()
53{
54 _current = readyList.getNext();
55 if (!_current) {
56 // There are no more processes, so return control to evaluate.
57 Fiber::primaryFiber()->run();
58 } else {
59 _current->popListNode();
60 // Switch to whatever Fiber is supposed to run this process. All
61 // Fibers which aren't running should be parked at this line.
62 _current->fiber()->run();
63 // If the current process hasn't been started yet, start it. This
64 // should always be true for methods, but may not be true for threads.
65 if (_current && !_current->running())
66 _current->run();
67 }
68}
69
70void
71Scheduler::ready(Process *p)
72{
73 // Clump methods together to minimize context switching.
74 if (p->procKind() == ::sc_core::SC_METHOD_PROC_)
75 readyList.pushFirst(p);
76 else
77 readyList.pushLast(p);
78
79 scheduleReadyEvent();
80}
81
82void
83Scheduler::requestUpdate(Channel *c)
84{
85 updateList.pushLast(c);
86 scheduleReadyEvent();
87}
88
89void
90Scheduler::scheduleReadyEvent()
91{
92 // Schedule the evaluate and update phases.
93 if (!readyEvent.scheduled()) {
94 panic_if(!eq, "Need to schedule ready, but no event manager.\n");
95 eq->schedule(&readyEvent, eq->getCurTick());
96 }
97}
98
99void
100Scheduler::runReady()
101{
102 bool empty = readyList.empty();
103
104 // The evaluation phase.
105 do {
106 yield();
107 } while (!readyList.empty());
108
109 if (!empty)
110 _numCycles++;
111
112 // The update phase.
113 update();
114
115 // The delta phase will happen naturally through the event queue.
116}
117
118void
119Scheduler::update()
120{
121 Channel *channel = updateList.getNext();
122 while (channel) {
123 channel->popListNode();
124 channel->update();
125 channel = updateList.getNext();
126 }
127}
128
129Scheduler scheduler;
130
131} // namespace sc_gem5