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/*
* Copyright (c) 2006 The Regents of The University of Michigan
* Copyright (c) 2013 Advanced Micro Devices, Inc.
* Copyright (c) 2013 Mark D. Hill and David A. Wood
* All rights reserved.
*
* 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: Nathan Binkert
* Steve Reinhardt
*/
#include <mutex>
#include <thread>
#include "base/misc.hh"
#include "base/pollevent.hh"
#include "base/types.hh"
#include "sim/async.hh"
#include "sim/eventq_impl.hh"
#include "sim/sim_events.hh"
#include "sim/sim_exit.hh"
#include "sim/simulate.hh"
#include "sim/stat_control.hh"
//! Mutex for handling async events.
std::mutex asyncEventMutex;
//! Global barrier for synchronizing threads entering/exiting the
//! simulation loop.
Barrier *threadBarrier;
//! forward declaration
Event *doSimLoop(EventQueue *);
/**
* The main function for all subordinate threads (i.e., all threads
* other than the main thread). These threads start by waiting on
* threadBarrier. Once all threads have arrived at threadBarrier,
* they enter the simulation loop concurrently. When they exit the
* loop, they return to waiting on threadBarrier. This process is
* repeated until the simulation terminates.
*/
static void
thread_loop(EventQueue *queue)
{
while (true) {
threadBarrier->wait();
doSimLoop(queue);
}
}
/** Simulate for num_cycles additional cycles. If num_cycles is -1
* (the default), do not limit simulation; some other event must
* terminate the loop. Exported to Python via SWIG.
* @return The SimLoopExitEvent that caused the loop to exit.
*/
GlobalSimLoopExitEvent *
simulate(Tick num_cycles)
{
// The first time simulate() is called from the Python code, we need to
// create a thread for each of event queues referenced by the
// instantiated sim objects.
static bool threads_initialized = false;
static std::vector<std::thread *> threads;
if (!threads_initialized) {
threadBarrier = new Barrier(numMainEventQueues);
// the main thread (the one we're currently running on)
// handles queue 0, so we only need to allocate new threads
// for queues 1..N-1. We'll call these the "subordinate" threads.
for (uint32_t i = 1; i < numMainEventQueues; i++) {
threads.push_back(new std::thread(thread_loop, mainEventQueue[i]));
}
threads_initialized = true;
}
inform("Entering event queue @ %d. Starting simulation...\n", curTick());
if (num_cycles < MaxTick - curTick())
num_cycles = curTick() + num_cycles;
else // counter would roll over or be set to MaxTick anyhow
num_cycles = MaxTick;
GlobalEvent *limit_event = new GlobalSimLoopExitEvent(num_cycles,
"simulate() limit reached", 0, 0);
GlobalSyncEvent *quantum_event = NULL;
if (numMainEventQueues > 1) {
if (simQuantum == 0) {
fatal("Quantum for multi-eventq simulation not specified");
}
quantum_event = new GlobalSyncEvent(simQuantum, simQuantum,
EventBase::Progress_Event_Pri, 0);
inParallelMode = true;
}
// all subordinate (created) threads should be waiting on the
// barrier; the arrival of the main thread here will satisfy the
// barrier, and all threads will enter doSimLoop in parallel
threadBarrier->wait();
Event *local_event = doSimLoop(mainEventQueue[0]);
assert(local_event != NULL);
inParallelMode = false;
// locate the global exit event and return it to Python
BaseGlobalEvent *global_event = local_event->globalEvent();
assert(global_event != NULL);
GlobalSimLoopExitEvent *global_exit_event =
dynamic_cast<GlobalSimLoopExitEvent *>(global_event);
assert(global_exit_event != NULL);
// if we didn't hit limit_event, delete it.
if (global_exit_event != limit_event) {
assert(limit_event->scheduled());
limit_event->deschedule();
delete limit_event;
}
//! Delete the simulation quantum event.
if (quantum_event != NULL) {
quantum_event->deschedule();
delete quantum_event;
}
return global_exit_event;
}
/**
* Test and clear the global async_event flag, such that each time the
* flag is cleared, only one thread returns true (and thus is assigned
* to handle the corresponding async event(s)).
*/
static bool
testAndClearAsyncEvent()
{
bool was_set = false;
asyncEventMutex.lock();
if (async_event) {
was_set = true;
async_event = false;
}
asyncEventMutex.unlock();
return was_set;
}
/**
* The main per-thread simulation loop. This loop is executed by all
* simulation threads (the main thread and the subordinate threads) in
* parallel.
*/
Event *
doSimLoop(EventQueue *eventq)
{
// set the per thread current eventq pointer
curEventQueue(eventq);
eventq->handleAsyncInsertions();
while (1) {
// there should always be at least one event (the SimLoopExitEvent
// we just scheduled) in the queue
assert(!eventq->empty());
assert(curTick() <= eventq->nextTick() &&
"event scheduled in the past");
Event *exit_event = eventq->serviceOne();
if (exit_event != NULL) {
return exit_event;
}
if (async_event && testAndClearAsyncEvent()) {
async_event = false;
if (async_statdump || async_statreset) {
Stats::schedStatEvent(async_statdump, async_statreset);
async_statdump = false;
async_statreset = false;
}
if (async_exit) {
async_exit = false;
exitSimLoop("user interrupt received");
}
if (async_io) {
async_io = false;
pollQueue.service();
}
if (async_exception) {
async_exception = false;
return NULL;
}
}
}
// not reached... only exit is return on SimLoopExitEvent
}
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