diff options
| -rw-r--r-- | src/base/SConscript | 2 | ||||
| -rw-r--r-- | src/base/fiber.cc | 148 | ||||
| -rw-r--r-- | src/base/fiber.hh | 106 | ||||
| -rw-r--r-- | src/base/fibertest.cc | 140 |
4 files changed, 396 insertions, 0 deletions
diff --git a/src/base/SConscript b/src/base/SConscript index a90b78486..b3205a6bb 100644 --- a/src/base/SConscript +++ b/src/base/SConscript @@ -46,6 +46,8 @@ if env['USE_FENV']: Source('fenv.c') if env['USE_PNG']: Source('pngwriter.cc') +Source('fiber.cc') +GTest('fibertest', 'fibertest.cc', 'fiber.cc') Source('framebuffer.cc') Source('hostinfo.cc') Source('inet.cc') diff --git a/src/base/fiber.cc b/src/base/fiber.cc new file mode 100644 index 000000000..f10f1fbfd --- /dev/null +++ b/src/base/fiber.cc @@ -0,0 +1,148 @@ +/* + * 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 "base/fiber.hh" + +#include <cerrno> +#include <cstring> + +#include "base/logging.hh" + +using namespace std; + +namespace +{ + +/* + * The PrimaryFiber class is a special case that attaches to the currently + * executing context. That makes handling the "primary" fiber, aka the one + * which most of gem5 is running under, no different than other Fibers. + */ +class PrimaryFiber : public Fiber +{ + public: + PrimaryFiber() : Fiber(nullptr, 0) { setStarted(); } + void main() { panic("PrimaryFiber main executed.\n"); } +}; + +PrimaryFiber _primaryFiber; + +// A pointer to whatever the currently executing Fiber is. +Fiber *_currentFiber = &_primaryFiber; + +// A pointer to the Fiber which is currently being started/initialized. +Fiber *startingFiber = nullptr; + +} // anonymous namespace + +void +Fiber::entryTrampoline() +{ + startingFiber->start(); +} + +Fiber::Fiber(size_t stack_size) : + link(primaryFiber()), + stack(stack_size ? new uint8_t[stack_size] : nullptr), + stackSize(stack_size), started(false), _finished(false) +{} + +Fiber::Fiber(Fiber *link, size_t stack_size) : + link(link), stack(stack_size ? new uint8_t[stack_size] : nullptr), + stackSize(stack_size), started(false), _finished(false) +{} + +Fiber::~Fiber() +{ + panic_if(stack && _currentFiber == this, "Fiber stack is in use."); + delete [] stack; +} + +void +Fiber::createContext() +{ + // Set up a context for the new fiber, starting it in the trampoline. + getcontext(&ctx); + ctx.uc_stack.ss_sp = stack; + ctx.uc_stack.ss_size = stackSize; + ctx.uc_link = nullptr; + makecontext(&ctx, &entryTrampoline, 0); + + // Swap to the new context so it can enter its start() function. It + // will then swap itself back out and return here. + startingFiber = this; + panic_if(!_currentFiber, "No active Fiber object."); + swapcontext(&_currentFiber->ctx, &ctx); + + // The new context is now ready and about to call main(). +} + +void +Fiber::start() +{ + // Avoid a dangling pointer. + startingFiber = nullptr; + + setStarted(); + + // Swap back to the parent context which is still considered "current", + // now that we're ready to go. + int ret M5_VAR_USED = swapcontext(&ctx, &_currentFiber->ctx); + panic_if(ret == -1, strerror(errno)); + + // Call main() when we're been reactivated for the first time. + main(); + + // main has returned, so this Fiber has finished. Switch to the "link" + // Fiber. + _finished = true; + link->run(); +} + +void +Fiber::run() +{ + panic_if(_finished, "Fiber has already run to completion."); + + // If we're already running this fiber, we're done. + if (_currentFiber == this) + return; + + if (!started) + createContext(); + + // Switch out of the current Fiber's context and this one's in. + Fiber *prev = _currentFiber; + Fiber *next = this; + _currentFiber = next; + swapcontext(&prev->ctx, &next->ctx); +} + +Fiber *Fiber::currentFiber() { return _currentFiber; } +Fiber *Fiber::primaryFiber() { return &_primaryFiber; } diff --git a/src/base/fiber.hh b/src/base/fiber.hh new file mode 100644 index 000000000..b9f0683a5 --- /dev/null +++ b/src/base/fiber.hh @@ -0,0 +1,106 @@ +/* + * 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 + */ + +#ifndef __BASE_FIBER_HH__ +#define __BASE_FIBER_HH__ + +#include <ucontext.h> + +#include <cstddef> +#include <cstdint> + +/** + * This class represents a fiber, which is a light weight sort of thread which + * is cooperatively scheduled and runs sequentially with other fibers, swapping + * in and out of a single actual thread of execution. + * + * To define your own threads, create a subclass of Fiber and override its + * main() function to do what you want your fiber to do. You can start it by + * calling its run() method which will stop your execution and start the other + * fiber in your place. + * + * If your main() function ends, that fiber will automatically switch to either + * the primary fiber, or to a particular fiber you specified at construction + * time, and your fiber is considered finished. + */ + +class Fiber +{ + public: + const static size_t DefaultStackSize = 0x50000; + + /// stack_size is the size of the stack available to this fiber. + /// link points to another fiber which will start executing when this + /// fiber's main function returns. + Fiber(size_t stack_size=DefaultStackSize); + Fiber(Fiber *link, size_t stack_size=DefaultStackSize); + + virtual ~Fiber(); + + /// Start executing the fiber represented by this object. This function + /// will "return" when the current fiber is switched back to later on. + void run(); + + /// Returns whether the "main" function of this fiber has finished. + /// + bool finished() const { return _finished; }; + + /// Get a pointer to the current running Fiber. + /// + static Fiber *currentFiber(); + /// Get a pointer to the primary Fiber. + /// This Fiber represents the thread of execution started by the OS, and + /// which has a Fiber attached to it after the fact. + static Fiber *primaryFiber(); + + protected: + /// This method is called when this fiber is first run. Override it to + /// give your fiber something to do. When main returns, the fiber will + /// mark itself as finished and switch to its link fiber. + virtual void main() = 0; + + void setStarted() { started = true; } + + private: + static void entryTrampoline(); + void start(); + + ucontext_t ctx; + Fiber *link; + + // The stack for this context, or a nullptr if allocated elsewhere. + uint8_t *stack; + size_t stackSize; + + bool started; + bool _finished; + void createContext(); +}; + +#endif // __BASE_FIBER_HH__ diff --git a/src/base/fibertest.cc b/src/base/fibertest.cc new file mode 100644 index 000000000..5ed13d425 --- /dev/null +++ b/src/base/fibertest.cc @@ -0,0 +1,140 @@ +/* + * 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 <gtest/gtest.h> + +#include <initializer_list> +#include <iostream> +#include <vector> + +#include "base/fiber.hh" + +class TestFiber : public Fiber +{ + public: + const char *name; + std::vector<Fiber *> next; + + TestFiber(const char *name, std::initializer_list<Fiber *> l); + + void checkExpected(); + void main(); +}; + +extern TestFiber a; +extern TestFiber b; +extern TestFiber c; + +TestFiber a("A", { &b, &a, Fiber::primaryFiber(), &b, &c }); +TestFiber b("B", { &a, &c }); +TestFiber c("C", { &a, Fiber::primaryFiber(), Fiber::primaryFiber() }); + +std::vector<TestFiber *>::iterator expectedIt; +std::vector<TestFiber *> expected({ + &a, &b, &a, &a, /* main Fiber, */ + &a, &b, &c, &a, &c, + /* main Fiber, */ &c, &c +}); + +TestFiber::TestFiber( + const char *name, std::initializer_list<Fiber *> l) : + name(name), next(l) +{} + +void +TestFiber::checkExpected() +{ + ASSERT_NE(expectedIt, expected.end()); + TestFiber *e = *expectedIt++; + EXPECT_EQ(e, this) << "Expected " << e->name << ", got " << name; +} + +void +TestFiber::main() +{ + checkExpected(); + for (auto &n : next) { + n->run(); + checkExpected(); + } +} + +TEST(Fiber, Switching) +{ + expectedIt = expected.begin(); + + a.run(); + EXPECT_EQ(expectedIt - expected.begin(), 4); + + a.run(); + EXPECT_EQ(expectedIt - expected.begin(), 9); + + c.run(); + EXPECT_EQ(expectedIt - expected.begin(), 10); + + EXPECT_FALSE(a.finished()); + EXPECT_FALSE(b.finished()); + EXPECT_FALSE(c.finished()); + + c.run(); + EXPECT_EQ(expected.end(), expectedIt) << + "Didn't exactly use up the expected Fiber sequence"; + + EXPECT_TRUE(c.finished()); +} + +int currentIndex = 0; + +class LinkedFiber : public Fiber +{ + public: + const int index; + LinkedFiber(Fiber *link, int index) : Fiber(link), index(index) {} + + void + main() + { + EXPECT_EQ(currentIndex, index); + currentIndex++; + } +}; + +TEST(Fiber, Linked) +{ + currentIndex = 0; + + LinkedFiber lf3(Fiber::primaryFiber(), 3); + LinkedFiber lf2(&lf3, 2); + LinkedFiber lf1(&lf2, 1); + LinkedFiber lf0(&lf1, 0); + + lf0.run(); + + EXPECT_EQ(currentIndex, 4); +} |