diff options
Diffstat (limited to 'indra/llcommon/llsingleton.h')
| -rw-r--r-- | indra/llcommon/llsingleton.h | 84 |
1 files changed, 47 insertions, 37 deletions
diff --git a/indra/llcommon/llsingleton.h b/indra/llcommon/llsingleton.h index 91c05bd5ed..25afccccc0 100644 --- a/indra/llcommon/llsingleton.h +++ b/indra/llcommon/llsingleton.h @@ -1,40 +1,42 @@ -/** +/** * @file llsingleton.h * * $LicenseInfo:firstyear=2002&license=viewerlgpl$ * 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 * $/LicenseInfo$ */ #ifndef LLSINGLETON_H #define LLSINGLETON_H +#include <boost/call_traits.hpp> #include <boost/noncopyable.hpp> #include <boost/unordered_set.hpp> +#include <functional> #include <initializer_list> #include <list> #include <typeinfo> #include <vector> #include "mutex.h" #include "lockstatic.h" +#include "apply.h" #include "llthread.h" // on_main_thread() -#include "llmainthreadtask.h" class LLSingletonBase: private boost::noncopyable { @@ -134,6 +136,17 @@ protected: // internal wrapper around calls to cleanupSingleton() void cleanup_(); + // This method is where we dispatch to LLMainThreadTask to acquire the + // subclass LLSingleton instance when the first getInstance() call is from + // a secondary thread. We delegate to the .cpp file to untangle header + // circularity. It accepts a std::function referencing the subclass + // getInstance() method -- which can't be virtual because it's static; we + // don't yet have an instance! For messaging, it also accepts the name of + // the subclass and the subclass method. + static LLSingletonBase* getInstanceForSecondaryThread( + const std::string& name, const std::string& method, + const std::function<LLSingletonBase*()>& getInstance); + // deleteSingleton() isn't -- and shouldn't be -- a virtual method. It's a // class static. However, given only Foo*, deleteAll() does need to be // able to reach Foo::deleteSingleton(). Make LLSingleton (which declares @@ -555,19 +568,11 @@ public: // Per the comment block above, dispatch to the main thread. loginfos({classname<DERIVED_TYPE>(), "::getInstance() dispatching to main thread"}); - auto instance = LLMainThreadTask::dispatch( - [](){ - // VERY IMPORTANT to call getInstance() on the main thread, - // rather than going straight to constructSingleton()! - // During the time window before mInitState is INITIALIZED, - // multiple requests might be queued. It's essential that, as - // the main thread processes them, only the FIRST such request - // actually constructs the instance -- every subsequent one - // simply returns the existing instance. - loginfos({classname<DERIVED_TYPE>(), - "::getInstance() on main thread"}); - return getInstance(); - }); + auto instance = static_cast<DERIVED_TYPE*>( + getInstanceForSecondaryThread( + classname<DERIVED_TYPE>(), + "getInstance()", + getInstance)); // record the dependency chain tracked on THIS thread, not the main // thread (consider a getInstance() overload with a tag param that // suppresses dep tracking when dispatched to the main thread) @@ -632,8 +637,14 @@ private: // Passes arguments to DERIVED_TYPE's constructor and sets appropriate // states, returning a pointer to the new instance. + // If we just let initParamSingleton_() infer its argument types, the + // compiler has trouble passing int and string literals. Use + // boost::call_traits::param_type to smooth parameter passing. This + // construction requires, though, that each invocation of this method + // explicitly specify template arguments, instead of inferring them. template <typename... Args> - static DERIVED_TYPE* initParamSingleton_(Args&&... args) + static LLSingletonBase* initParamSingleton_( + typename boost::call_traits<Args>::param_type... args) { // In case racing threads both call initParamSingleton() at the same // time, serialize them. One should initialize; the other should see @@ -652,7 +663,7 @@ private: // on the main thread, simply construct instance while holding lock super::logdebugs({super::template classname<DERIVED_TYPE>(), "::initParamSingleton()"}); - super::constructSingleton(lk, std::forward<Args>(args)...); + super::constructSingleton(lk, args...); return lk->mInstance; } else @@ -665,20 +676,19 @@ private: lk.unlock(); super::loginfos({super::template classname<DERIVED_TYPE>(), "::initParamSingleton() dispatching to main thread"}); - // Normally it would be the height of folly to reference-bind - // 'args' into a lambda to be executed on some other thread! By - // the time that thread executed the lambda, the references would - // all be dangling, and Bad Things would result. But - // LLMainThreadTask::dispatch() promises to block until the passed - // task has completed. So in this case we know the references will - // remain valid until the lambda has run, so we dare to bind - // references. - auto instance = LLMainThreadTask::dispatch( - [&](){ - super::loginfos({super::template classname<DERIVED_TYPE>(), - "::initParamSingleton() on main thread"}); - return initParamSingleton_(std::forward<Args>(args)...); - }); + auto instance = static_cast<DERIVED_TYPE*>( + super::getInstanceForSecondaryThread( + super::template classname<DERIVED_TYPE>(), + "initParamSingleton()", + // This lambda does what std::bind() is supposed to do -- + // but when the actual parameter is (e.g.) a string + // literal, type inference makes it fail. Apply param_type + // to each incoming type to make it work. + [args=std::tuple<typename boost::call_traits<Args>::param_type...>(args...)] + () + { + return LL::apply(initParamSingleton_<Args...>, args); + })); super::loginfos({super::template classname<DERIVED_TYPE>(), "::initParamSingleton() returning on requesting thread"}); return instance; @@ -695,7 +705,7 @@ public: template <typename... Args> static DERIVED_TYPE& initParamSingleton(Args&&... args) { - return *initParamSingleton_(std::forward<Args>(args)...); + return *static_cast<DERIVED_TYPE*>(initParamSingleton_<Args...>(args...)); } static DERIVED_TYPE* getInstance() @@ -841,7 +851,7 @@ private: \ // Relatively unsafe singleton implementation that is much faster // and simpler than LLSingleton, but has no dependency tracking -// or inherent thread safety and requires manual invocation of +// or inherent thread safety and requires manual invocation of // createInstance before first use. template<class T> class LLSimpleton |