1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ 2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */ 3 /* This Source Code Form is subject to the terms of the Mozilla Public 4 * License, v. 2.0. If a copy of the MPL was not distributed with this 5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ 6 7 #ifndef nsThreadSyncDispatch_h_ 8 #define nsThreadSyncDispatch_h_ 9 10 #include "mozilla/Atomics.h" 11 #include "mozilla/DebugOnly.h" 12 13 #include "nsThreadUtils.h" 14 #include "LeakRefPtr.h" 15 16 class nsThreadSyncDispatch : public mozilla::Runnable { 17 public: nsThreadSyncDispatch(already_AddRefed<nsIEventTarget> aOrigin,already_AddRefed<nsIRunnable> && aTask)18 nsThreadSyncDispatch(already_AddRefed<nsIEventTarget> aOrigin, 19 already_AddRefed<nsIRunnable>&& aTask) 20 : Runnable("nsThreadSyncDispatch"), 21 mOrigin(aOrigin), 22 mSyncTask(std::move(aTask)), 23 mIsPending(true) {} 24 IsPending()25 bool IsPending() { 26 // This is an atomic acquire on the origin thread. 27 return mIsPending; 28 } 29 30 private: Run()31 NS_IMETHOD Run() override { 32 if (nsCOMPtr<nsIRunnable> task = mSyncTask.take()) { 33 MOZ_ASSERT(!mSyncTask); 34 35 mozilla::DebugOnly<nsresult> result = task->Run(); 36 MOZ_ASSERT(NS_SUCCEEDED(result), "task in sync dispatch should not fail"); 37 38 // We must release the task here to ensure that when the original 39 // thread is unblocked, this task has been released. 40 task = nullptr; 41 42 // This is an atomic release on the target thread. 43 mIsPending = false; 44 45 // unblock the origin thread 46 mOrigin->Dispatch(this, NS_DISPATCH_NORMAL); 47 } 48 49 return NS_OK; 50 } 51 52 nsCOMPtr<nsIEventTarget> mOrigin; 53 // The task is leaked by default when Run() is not called, because 54 // otherwise we may release it in an incorrect thread. 55 mozilla::LeakRefPtr<nsIRunnable> mSyncTask; 56 mozilla::Atomic<bool, mozilla::ReleaseAcquire> mIsPending; 57 }; 58 59 #endif // nsThreadSyncDispatch_h_ 60