/** * @file llcoros.h * @author Nat Goodspeed * @date 2009-06-02 * @brief Manage running boost::coroutine instances * * $LicenseInfo:firstyear=2009&license=viewerlgpl$ * Second Life Viewer Source Code * Copyright (C) 2010, Linden Research, Inc. * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; * version 2.1 of the License only. * * This library is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this library; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA * * Linden Research, Inc., 945 Battery Street, San Francisco, CA 94111 USA * $/LicenseInfo$ */ #if ! defined(LL_LLCOROS_H) #define LL_LLCOROS_H #include "llexception.h" #include <boost/fiber/fss.hpp> #include <boost/fiber/future/promise.hpp> #include <boost/fiber/future/future.hpp> #include "mutex.h" #include "llsingleton.h" #include "llinstancetracker.h" #include <boost/function.hpp> #include <string> #include <exception> #include <queue> // e.g. #include LLCOROS_MUTEX_HEADER #define LLCOROS_MUTEX_HEADER <boost/fiber/mutex.hpp> #define LLCOROS_CONDVAR_HEADER <boost/fiber/condition_variable.hpp> namespace boost { namespace fibers { class mutex; enum class cv_status; class condition_variable; } } /** * Registry of named Boost.Coroutine instances * * The Boost.Coroutine library supports the general case of a coroutine * accepting arbitrary parameters and yielding multiple (sets of) results. For * such use cases, it's natural for the invoking code to retain the coroutine * instance: the consumer repeatedly calls into the coroutine, perhaps passing * new parameter values, prompting it to yield its next result. * * Our typical coroutine usage is different, though. For us, coroutines * provide an alternative to the @c Responder pattern. Our typical coroutine * has @c void return, invoked in fire-and-forget mode: the handler for some * user gesture launches the coroutine and promptly returns to the main loop. * The coroutine initiates some action that will take multiple frames (e.g. a * capability request), waits for its result, processes it and silently steals * away. * * This usage poses two (related) problems: * * # Who should own the coroutine instance? If it's simply local to the * handler code that launches it, return from the handler will destroy the * coroutine object, terminating the coroutine. * # Once the coroutine terminates, in whatever way, who's responsible for * cleaning up the coroutine object? * * LLCoros is a Singleton collection of currently-active coroutine instances. * Each has a name. You ask LLCoros to launch a new coroutine with a suggested * name prefix; from your prefix it generates a distinct name, registers the * new coroutine and returns the actual name. * * The name * can provide diagnostic info: we can look up the name of the * currently-running coroutine. */ class LL_COMMON_API LLCoros: public LLSingleton<LLCoros> { LLSINGLETON(LLCoros); ~LLCoros(); void cleanupSingleton(); public: /// The viewer's use of the term "coroutine" became deeply embedded before /// the industry term "fiber" emerged to distinguish userland threads from /// simpler, more transient kinds of coroutines. Semantically they've /// always been fibers. But at this point in history, we're pretty much /// stuck with the term "coroutine." typedef boost::fibers::fiber coro; /// Canonical callable type typedef boost::function<void()> callable_t; /** * Create and start running a new coroutine with specified name. The name * string you pass is a suggestion; it will be tweaked for uniqueness. The * actual name is returned to you. * * Usage looks like this, for (e.g.) two coroutine parameters: * @code * class MyClass * { * public: * ... * // Do NOT NOT NOT accept reference params! * // Pass by value only! * void myCoroutineMethod(std::string, LLSD); * ... * }; * ... * std::string name = LLCoros::instance().launch( * "mycoro", boost::bind(&MyClass::myCoroutineMethod, this, * "somestring", LLSD(17)); * @endcode * * Your function/method can accept any parameters you want -- but ONLY BY * VALUE! Reference parameters are a BAD IDEA! You Have Been Warned. See * DEV-32777 comments for an explanation. * * Pass a nullary callable. It works to directly pass a nullary free * function (or static method); for other cases use a lambda expression, * std::bind() or boost::bind(). Of course, for a non-static class method, * the first parameter must be the class instance. Any other parameters * should be passed via the enclosing expression. * * launch() tweaks the suggested name so it won't collide with any * existing coroutine instance, creates the coroutine instance, registers * it with the tweaked name and runs it until its first wait. At that * point it returns the tweaked name. */ std::string launch(const std::string& prefix, const callable_t& callable); /** * Abort a running coroutine by name. Normally, when a coroutine either * runs to completion or terminates with an exception, LLCoros quietly * cleans it up. This is for use only when you must explicitly interrupt * one prematurely. Returns @c true if the specified name was found and * still running at the time. */ // bool kill(const std::string& name); /** * From within a coroutine, look up the (tweaked) name string by which * this coroutine is registered. Returns the empty string if not found * (e.g. if the coroutine was launched by hand rather than using * LLCoros::launch()). */ static std::string getName(); /** * rethrow() is called by the thread's main fiber to propagate an * exception from any coroutine into the main fiber, where it can engage * the normal unhandled-exception machinery, up to and including crash * reporting. * * LLCoros maintains a queue of otherwise-uncaught exceptions from * terminated coroutines. Each call to rethrow() pops the first of those * and rethrows it. When the queue is empty (normal case), rethrow() is a * no-op. */ void rethrow(); /** * This variation returns a name suitable for log messages: the explicit * name for an explicitly-launched coroutine, or "mainN" for the default * coroutine on a thread. */ static std::string logname(); /** * For delayed initialization. To be clear, this will only affect * coroutines launched @em after this point. The underlying facility * provides no way to alter the stack size of any running coroutine. */ void setStackSize(S32 stacksize); /// diagnostic void printActiveCoroutines(const std::string& when=std::string()); /// get the current coro::id for those who really really care static coro::id get_self(); /** * Most coroutines, most of the time, don't "consume" the events for which * they're suspending. This way, an arbitrary number of listeners (whether * coroutines or simple callbacks) can be registered on a particular * LLEventPump, every listener responding to each of the events on that * LLEventPump. But a particular coroutine can assert that it will consume * each event for which it suspends. (See also llcoro::postAndSuspend(), * llcoro::VoidListener) */ static void set_consuming(bool consuming); static bool get_consuming(); /** * RAII control of the consuming flag */ class OverrideConsuming { public: OverrideConsuming(bool consuming): mPrevConsuming(get_consuming()) { set_consuming(consuming); } OverrideConsuming(const OverrideConsuming&) = delete; ~OverrideConsuming() { set_consuming(mPrevConsuming); } private: bool mPrevConsuming; }; /// set string coroutine status for diagnostic purposes static void setStatus(const std::string& status); static std::string getStatus(); /// RAII control of status class TempStatus { public: TempStatus(const std::string& status): mOldStatus(getStatus()) { setStatus(status); } TempStatus(const TempStatus&) = delete; ~TempStatus() { setStatus(mOldStatus); } private: std::string mOldStatus; }; /// thrown by checkStop() // It may sound ironic that Stop is derived from LLContinueError, but the // point is that LLContinueError is the category of exception that should // not immediately crash the viewer. Stop and its subclasses are to notify // coroutines that the viewer intends to shut down. The expected response // is to terminate the coroutine, rather than abort the viewer. struct Stop: public LLContinueError { Stop(const std::string& what): LLContinueError(what) {} }; /// early stages struct Stopping: public Stop { Stopping(const std::string& what): Stop(what) {} }; /// cleaning up struct Stopped: public Stop { Stopped(const std::string& what): Stop(what) {} }; /// cleaned up -- not much survives! struct Shutdown: public Stop { Shutdown(const std::string& what): Stop(what) {} }; /// Call this intermittently if there's a chance your coroutine might /// continue running into application shutdown. Throws Stop if LLCoros has /// been cleaned up. static void checkStop(); /** * Aliases for promise and future. An older underlying future implementation * required us to wrap future; that's no longer needed. However -- if it's * important to restore kill() functionality, we might need to provide a * proxy, so continue using the aliases. */ template <typename T> using Promise = boost::fibers::promise<T>; template <typename T> using Future = boost::fibers::future<T>; template <typename T> static Future<T> getFuture(Promise<T>& promise) { return promise.get_future(); } // use mutex, lock, condition_variable suitable for coroutines using Mutex = boost::fibers::mutex; using LockType = std::unique_lock<Mutex>; using cv_status = boost::fibers::cv_status; using ConditionVariable = boost::fibers::condition_variable; /// for data local to each running coroutine template <typename T> using local_ptr = boost::fibers::fiber_specific_ptr<T>; private: std::string generateDistinctName(const std::string& prefix) const; void toplevel(std::string name, callable_t callable); struct CoroData; static CoroData& get_CoroData(const std::string& caller); void saveException(const std::string& name, std::exception_ptr exc); struct ExceptionData { ExceptionData(const std::string& nm, std::exception_ptr exc): name(nm), exception(exc) {} // name of coroutine that originally threw this exception std::string name; // the thrown exception std::exception_ptr exception; }; std::queue<ExceptionData> mExceptionQueue; S32 mStackSize; // coroutine-local storage, as it were: one per coro we track struct CoroData: public LLInstanceTracker<CoroData, std::string> { CoroData(const std::string& name); CoroData(int n); // tweaked name of the current coroutine const std::string mName; // set_consuming() state bool mConsuming; // setStatus() state std::string mStatus; F64 mCreationTime; // since epoch }; // Identify the current coroutine's CoroData. This local_ptr isn't static // because it's a member of an LLSingleton, and we rely on it being // cleaned up in proper dependency order. local_ptr<CoroData> mCurrent; }; namespace llcoro { inline std::string logname() { return LLCoros::logname(); } } // llcoro #endif /* ! defined(LL_LLCOROS_H) */