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/*
* Copyright 2018 Google, Inc.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met: redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer;
* redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution;
* neither the name of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Authors: Gabe Black
*/
#include "systemc/core/scheduler.hh"
#include "base/fiber.hh"
#include "base/logging.hh"
#include "sim/eventq.hh"
namespace sc_gem5
{
Scheduler::Scheduler() :
eq(nullptr), readyEvent(this, false, EventBase::Default_Pri + 1),
_numCycles(0), _current(nullptr), initReady(false)
{}
void
Scheduler::prepareForInit()
{
for (Process *p = toFinalize.getNext(); p; p = toFinalize.getNext()) {
p->finalize();
p->popListNode();
}
for (Process *p = initList.getNext(); p; p = initList.getNext()) {
p->finalize();
ready(p);
}
initReady = true;
}
void
Scheduler::reg(Process *p)
{
if (initReady) {
// If we're past initialization, finalize static sensitivity.
p->finalize();
// Mark the process as ready.
ready(p);
} else {
// Otherwise, record that this process should be initialized once we
// get there.
initList.pushLast(p);
}
}
void
Scheduler::dontInitialize(Process *p)
{
if (initReady) {
// Pop this process off of the ready list.
p->popListNode();
} else {
// Push this process onto the list of processes which still need
// their static sensitivity to be finalized. That implicitly pops it
// off the list of processes to be initialized/marked ready.
toFinalize.pushLast(p);
}
}
void
Scheduler::yield()
{
_current = readyList.getNext();
if (!_current) {
// There are no more processes, so return control to evaluate.
Fiber::primaryFiber()->run();
} else {
_current->popListNode();
// Switch to whatever Fiber is supposed to run this process. All
// Fibers which aren't running should be parked at this line.
_current->fiber()->run();
// If the current process hasn't been started yet, start it. This
// should always be true for methods, but may not be true for threads.
if (_current && !_current->running())
_current->run();
}
}
void
Scheduler::ready(Process *p)
{
// Clump methods together to minimize context switching.
if (p->procKind() == ::sc_core::SC_METHOD_PROC_)
readyList.pushFirst(p);
else
readyList.pushLast(p);
scheduleReadyEvent();
}
void
Scheduler::requestUpdate(Channel *c)
{
updateList.pushLast(c);
scheduleReadyEvent();
}
void
Scheduler::scheduleReadyEvent()
{
// Schedule the evaluate and update phases.
if (!readyEvent.scheduled()) {
panic_if(!eq, "Need to schedule ready, but no event manager.\n");
eq->schedule(&readyEvent, eq->getCurTick());
}
}
void
Scheduler::runReady()
{
bool empty = readyList.empty();
// The evaluation phase.
do {
yield();
} while (!readyList.empty());
if (!empty)
_numCycles++;
// The update phase.
update();
// The delta phase will happen naturally through the event queue.
}
void
Scheduler::update()
{
Channel *channel = updateList.getNext();
while (channel) {
channel->popListNode();
channel->update();
channel = updateList.getNext();
}
}
Scheduler scheduler;
} // namespace sc_gem5
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