fiber.cc revision 12787
112787Sgabeblack@google.com/* 212787Sgabeblack@google.com * Copyright 2018 Google, Inc. 312787Sgabeblack@google.com * 412787Sgabeblack@google.com * Redistribution and use in source and binary forms, with or without 512787Sgabeblack@google.com * modification, are permitted provided that the following conditions are 612787Sgabeblack@google.com * met: redistributions of source code must retain the above copyright 712787Sgabeblack@google.com * notice, this list of conditions and the following disclaimer; 812787Sgabeblack@google.com * redistributions in binary form must reproduce the above copyright 912787Sgabeblack@google.com * notice, this list of conditions and the following disclaimer in the 1012787Sgabeblack@google.com * documentation and/or other materials provided with the distribution; 1112787Sgabeblack@google.com * neither the name of the copyright holders nor the names of its 1212787Sgabeblack@google.com * contributors may be used to endorse or promote products derived from 1312787Sgabeblack@google.com * this software without specific prior written permission. 1412787Sgabeblack@google.com * 1512787Sgabeblack@google.com * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 1612787Sgabeblack@google.com * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 1712787Sgabeblack@google.com * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 1812787Sgabeblack@google.com * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 1912787Sgabeblack@google.com * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 2012787Sgabeblack@google.com * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 2112787Sgabeblack@google.com * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 2212787Sgabeblack@google.com * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 2312787Sgabeblack@google.com * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 2412787Sgabeblack@google.com * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 2512787Sgabeblack@google.com * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 2612787Sgabeblack@google.com * 2712787Sgabeblack@google.com * Authors: Gabe Black 2812787Sgabeblack@google.com */ 2912787Sgabeblack@google.com 3012787Sgabeblack@google.com#include "base/fiber.hh" 3112787Sgabeblack@google.com 3212787Sgabeblack@google.com#include <cerrno> 3312787Sgabeblack@google.com#include <cstring> 3412787Sgabeblack@google.com 3512787Sgabeblack@google.com#include "base/logging.hh" 3612787Sgabeblack@google.com 3712787Sgabeblack@google.comusing namespace std; 3812787Sgabeblack@google.com 3912787Sgabeblack@google.comnamespace 4012787Sgabeblack@google.com{ 4112787Sgabeblack@google.com 4212787Sgabeblack@google.com/* 4312787Sgabeblack@google.com * The PrimaryFiber class is a special case that attaches to the currently 4412787Sgabeblack@google.com * executing context. That makes handling the "primary" fiber, aka the one 4512787Sgabeblack@google.com * which most of gem5 is running under, no different than other Fibers. 4612787Sgabeblack@google.com */ 4712787Sgabeblack@google.comclass PrimaryFiber : public Fiber 4812787Sgabeblack@google.com{ 4912787Sgabeblack@google.com public: 5012787Sgabeblack@google.com PrimaryFiber() : Fiber(nullptr, 0) { setStarted(); } 5112787Sgabeblack@google.com void main() { panic("PrimaryFiber main executed.\n"); } 5212787Sgabeblack@google.com}; 5312787Sgabeblack@google.com 5412787Sgabeblack@google.comPrimaryFiber _primaryFiber; 5512787Sgabeblack@google.com 5612787Sgabeblack@google.com// A pointer to whatever the currently executing Fiber is. 5712787Sgabeblack@google.comFiber *_currentFiber = &_primaryFiber; 5812787Sgabeblack@google.com 5912787Sgabeblack@google.com// A pointer to the Fiber which is currently being started/initialized. 6012787Sgabeblack@google.comFiber *startingFiber = nullptr; 6112787Sgabeblack@google.com 6212787Sgabeblack@google.com} // anonymous namespace 6312787Sgabeblack@google.com 6412787Sgabeblack@google.comvoid 6512787Sgabeblack@google.comFiber::entryTrampoline() 6612787Sgabeblack@google.com{ 6712787Sgabeblack@google.com startingFiber->start(); 6812787Sgabeblack@google.com} 6912787Sgabeblack@google.com 7012787Sgabeblack@google.comFiber::Fiber(size_t stack_size) : 7112787Sgabeblack@google.com link(primaryFiber()), 7212787Sgabeblack@google.com stack(stack_size ? new uint8_t[stack_size] : nullptr), 7312787Sgabeblack@google.com stackSize(stack_size), started(false), _finished(false) 7412787Sgabeblack@google.com{} 7512787Sgabeblack@google.com 7612787Sgabeblack@google.comFiber::Fiber(Fiber *link, size_t stack_size) : 7712787Sgabeblack@google.com link(link), stack(stack_size ? new uint8_t[stack_size] : nullptr), 7812787Sgabeblack@google.com stackSize(stack_size), started(false), _finished(false) 7912787Sgabeblack@google.com{} 8012787Sgabeblack@google.com 8112787Sgabeblack@google.comFiber::~Fiber() 8212787Sgabeblack@google.com{ 8312787Sgabeblack@google.com panic_if(stack && _currentFiber == this, "Fiber stack is in use."); 8412787Sgabeblack@google.com delete [] stack; 8512787Sgabeblack@google.com} 8612787Sgabeblack@google.com 8712787Sgabeblack@google.comvoid 8812787Sgabeblack@google.comFiber::createContext() 8912787Sgabeblack@google.com{ 9012787Sgabeblack@google.com // Set up a context for the new fiber, starting it in the trampoline. 9112787Sgabeblack@google.com getcontext(&ctx); 9212787Sgabeblack@google.com ctx.uc_stack.ss_sp = stack; 9312787Sgabeblack@google.com ctx.uc_stack.ss_size = stackSize; 9412787Sgabeblack@google.com ctx.uc_link = nullptr; 9512787Sgabeblack@google.com makecontext(&ctx, &entryTrampoline, 0); 9612787Sgabeblack@google.com 9712787Sgabeblack@google.com // Swap to the new context so it can enter its start() function. It 9812787Sgabeblack@google.com // will then swap itself back out and return here. 9912787Sgabeblack@google.com startingFiber = this; 10012787Sgabeblack@google.com panic_if(!_currentFiber, "No active Fiber object."); 10112787Sgabeblack@google.com swapcontext(&_currentFiber->ctx, &ctx); 10212787Sgabeblack@google.com 10312787Sgabeblack@google.com // The new context is now ready and about to call main(). 10412787Sgabeblack@google.com} 10512787Sgabeblack@google.com 10612787Sgabeblack@google.comvoid 10712787Sgabeblack@google.comFiber::start() 10812787Sgabeblack@google.com{ 10912787Sgabeblack@google.com // Avoid a dangling pointer. 11012787Sgabeblack@google.com startingFiber = nullptr; 11112787Sgabeblack@google.com 11212787Sgabeblack@google.com setStarted(); 11312787Sgabeblack@google.com 11412787Sgabeblack@google.com // Swap back to the parent context which is still considered "current", 11512787Sgabeblack@google.com // now that we're ready to go. 11612787Sgabeblack@google.com int ret M5_VAR_USED = swapcontext(&ctx, &_currentFiber->ctx); 11712787Sgabeblack@google.com panic_if(ret == -1, strerror(errno)); 11812787Sgabeblack@google.com 11912787Sgabeblack@google.com // Call main() when we're been reactivated for the first time. 12012787Sgabeblack@google.com main(); 12112787Sgabeblack@google.com 12212787Sgabeblack@google.com // main has returned, so this Fiber has finished. Switch to the "link" 12312787Sgabeblack@google.com // Fiber. 12412787Sgabeblack@google.com _finished = true; 12512787Sgabeblack@google.com link->run(); 12612787Sgabeblack@google.com} 12712787Sgabeblack@google.com 12812787Sgabeblack@google.comvoid 12912787Sgabeblack@google.comFiber::run() 13012787Sgabeblack@google.com{ 13112787Sgabeblack@google.com panic_if(_finished, "Fiber has already run to completion."); 13212787Sgabeblack@google.com 13312787Sgabeblack@google.com // If we're already running this fiber, we're done. 13412787Sgabeblack@google.com if (_currentFiber == this) 13512787Sgabeblack@google.com return; 13612787Sgabeblack@google.com 13712787Sgabeblack@google.com if (!started) 13812787Sgabeblack@google.com createContext(); 13912787Sgabeblack@google.com 14012787Sgabeblack@google.com // Switch out of the current Fiber's context and this one's in. 14112787Sgabeblack@google.com Fiber *prev = _currentFiber; 14212787Sgabeblack@google.com Fiber *next = this; 14312787Sgabeblack@google.com _currentFiber = next; 14412787Sgabeblack@google.com swapcontext(&prev->ctx, &next->ctx); 14512787Sgabeblack@google.com} 14612787Sgabeblack@google.com 14712787Sgabeblack@google.comFiber *Fiber::currentFiber() { return _currentFiber; } 14812787Sgabeblack@google.comFiber *Fiber::primaryFiber() { return &_primaryFiber; } 149