1 files changed, 251 insertions, 0 deletions
diff --git a/dom/workers/JSExecutionManager.cpp b/dom/workers/JSExecutionManager.cpp
new file mode 100644
index 0000000000..4a67a3a3d2
--- /dev/null
+++ b/dom/workers/JSExecutionManager.cpp
@@ -0,0 +1,251 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/dom/JSExecutionManager.h"
+
+#include "WorkerCommon.h"
+#include "WorkerPrivate.h"
+
+#include "mozilla/dom/DocGroup.h"
+#include "mozilla/StaticPrefs_dom.h"
+#include "mozilla/StaticPtr.h"
+
+namespace mozilla::dom {
+
+JSExecutionManager* JSExecutionManager::mCurrentMTManager;
+
+const uint32_t kTimeSliceExpirationMS = 50;
+
+using RequestState = JSExecutionManager::RequestState;
+
+static StaticRefPtr<JSExecutionManager> sSABSerializationManager;
+
+void JSExecutionManager::Initialize() {
+  if (StaticPrefs::dom_workers_serialized_sab_access()) {
+    sSABSerializationManager = MakeRefPtr<JSExecutionManager>(1);
+  }
+}
+
+void JSExecutionManager::Shutdown() { sSABSerializationManager = nullptr; }
+
+JSExecutionManager* JSExecutionManager::GetSABSerializationManager() {
+  return sSABSerializationManager.get();
+}
+
+RequestState JSExecutionManager::RequestJSThreadExecution() {
+  if (NS_IsMainThread()) {
+    return RequestJSThreadExecutionMainThread();
+  }
+
+  WorkerPrivate* workerPrivate = GetCurrentThreadWorkerPrivate();
+
+  if (!workerPrivate || workerPrivate->GetExecutionGranted()) {
+    return RequestState::ExecutingAlready;
+  }
+
+  MutexAutoLock lock(mExecutionQueueMutex);
+  MOZ_ASSERT(mMaxRunning >= mRunning);
+
+  if ((mExecutionQueue.size() + (mMainThreadAwaitingExecution ? 1 : 0)) <
+      size_t(mMaxRunning - mRunning)) {
+    // There's slots ready for things to run, execute right away.
+    workerPrivate->SetExecutionGranted(true);
+    workerPrivate->ScheduleTimeSliceExpiration(kTimeSliceExpirationMS);
+
+    mRunning++;
+    return RequestState::Granted;
+  }
+
+  mExecutionQueue.push_back(workerPrivate);
+
+  TimeStamp waitStart = TimeStamp::Now();
+
+  while (mRunning >= mMaxRunning || (workerPrivate != mExecutionQueue.front() ||
+                                     mMainThreadAwaitingExecution)) {
+    // If there is no slots available, the main thread is awaiting permission
+    // or we are not first in line for execution, wait until notified.
+    mExecutionQueueCondVar.Wait(TimeDuration::FromMilliseconds(500));
+    if ((TimeStamp::Now() - waitStart) > TimeDuration::FromSeconds(20)) {
+      // Crash so that these types of situations are actually caught in the
+      // crash reporter.
+      MOZ_CRASH();
+    }
+  }
+
+  workerPrivate->SetExecutionGranted(true);
+  workerPrivate->ScheduleTimeSliceExpiration(kTimeSliceExpirationMS);
+
+  mExecutionQueue.pop_front();
+  mRunning++;
+  if (mRunning < mMaxRunning) {
+    // If a thread woke up before that wasn't first in line it will have gone
+    // back to sleep, if there's more slots available, wake it now.
+    mExecutionQueueCondVar.NotifyAll();
+  }
+
+  return RequestState::Granted;
+}
+
+void JSExecutionManager::YieldJSThreadExecution() {
+  if (NS_IsMainThread()) {
+    MOZ_ASSERT(mMainThreadIsExecuting);
+    mMainThreadIsExecuting = false;
+
+    MutexAutoLock lock(mExecutionQueueMutex);
+    mRunning--;
+    mExecutionQueueCondVar.NotifyAll();
+    return;
+  }
+
+  WorkerPrivate* workerPrivate = GetCurrentThreadWorkerPrivate();
+
+  if (!workerPrivate) {
+    return;
+  }
+
+  MOZ_ASSERT(workerPrivate->GetExecutionGranted());
+
+  workerPrivate->CancelTimeSliceExpiration();
+
+  MutexAutoLock lock(mExecutionQueueMutex);
+  mRunning--;
+  mExecutionQueueCondVar.NotifyAll();
+  workerPrivate->SetExecutionGranted(false);
+}
+
+bool JSExecutionManager::YieldJSThreadExecutionIfGranted() {
+  if (NS_IsMainThread()) {
+    if (mMainThreadIsExecuting) {
+      YieldJSThreadExecution();
+      return true;
+    }
+    return false;
+  }
+
+  WorkerPrivate* workerPrivate = GetCurrentThreadWorkerPrivate();
+
+  if (workerPrivate && workerPrivate->GetExecutionGranted()) {
+    YieldJSThreadExecution();
+    return true;
+  }
+
+  return false;
+}
+
+RequestState JSExecutionManager::RequestJSThreadExecutionMainThread() {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (mMainThreadIsExecuting) {
+    return RequestState::ExecutingAlready;
+  }
+
+  MutexAutoLock lock(mExecutionQueueMutex);
+  MOZ_ASSERT(mMaxRunning >= mRunning);
+
+  if ((mMaxRunning - mRunning) > 0) {
+    // If there's any slots available run, the main thread always takes
+    // precedence over any worker threads.
+    mRunning++;
+    mMainThreadIsExecuting = true;
+    return RequestState::Granted;
+  }
+
+  mMainThreadAwaitingExecution = true;
+
+  TimeStamp waitStart = TimeStamp::Now();
+
+  while (mRunning >= mMaxRunning) {
+    if ((TimeStamp::Now() - waitStart) > TimeDuration::FromSeconds(20)) {
+      // Crash so that these types of situations are actually caught in the
+      // crash reporter.
+      MOZ_CRASH();
+    }
+    mExecutionQueueCondVar.Wait(TimeDuration::FromMilliseconds(500));
+  }
+
+  mMainThreadAwaitingExecution = false;
+  mMainThreadIsExecuting = true;
+
+  mRunning++;
+  if (mRunning < mMaxRunning) {
+    // If a thread woke up before that wasn't first in line it will have gone
+    // back to sleep, if there's more slots available, wake it now.
+    mExecutionQueueCondVar.NotifyAll();
+  }
+
+  return RequestState::Granted;
+}
+
+AutoRequestJSThreadExecution::AutoRequestJSThreadExecution(
+    nsIGlobalObject* aGlobalObject, bool aIsMainThread) {
+  JSExecutionManager* manager = nullptr;
+
+  mIsMainThread = aIsMainThread;
+  if (mIsMainThread) {
+    mOldGrantingManager = JSExecutionManager::mCurrentMTManager;
+
+    nsPIDOMWindowInner* innerWindow = nullptr;
+    if (aGlobalObject) {
+      innerWindow = aGlobalObject->AsInnerWindow();
+    }
+
+    DocGroup* docGroup = nullptr;
+    if (innerWindow) {
+      docGroup = innerWindow->GetDocGroup();
+    }
+
+    if (docGroup) {
+      manager = docGroup->GetExecutionManager();
+    }
+
+    if (JSExecutionManager::mCurrentMTManager == manager) {
+      return;
+    }
+
+    if (JSExecutionManager::mCurrentMTManager) {
+      JSExecutionManager::mCurrentMTManager->YieldJSThreadExecution();
+      JSExecutionManager::mCurrentMTManager = nullptr;
+    }
+  } else {
+    WorkerPrivate* workerPrivate = GetCurrentThreadWorkerPrivate();
+
+    if (workerPrivate) {
+      manager = workerPrivate->GetExecutionManager();
+    }
+  }
+
+  if (manager &&
+      (manager->RequestJSThreadExecution() == RequestState::Granted)) {
+    if (NS_IsMainThread()) {
+      // Make sure we restore permission on destruction if needed.
+      JSExecutionManager::mCurrentMTManager = manager;
+    }
+    mExecutionGrantingManager = std::move(manager);
+  }
+}
+
+AutoYieldJSThreadExecution::AutoYieldJSThreadExecution() {
+  JSExecutionManager* manager = nullptr;
+
+  if (NS_IsMainThread()) {
+    manager = JSExecutionManager::mCurrentMTManager;
+  } else {
+    WorkerPrivate* workerPrivate = GetCurrentThreadWorkerPrivate();
+
+    if (workerPrivate) {
+      manager = workerPrivate->GetExecutionManager();
+    }
+  }
+
+  if (manager && manager->YieldJSThreadExecutionIfGranted()) {
+    mExecutionGrantingManager = std::move(manager);
+    if (NS_IsMainThread()) {
+      JSExecutionManager::mCurrentMTManager = nullptr;
+    }
+  }
+}
+
+}  // namespace mozilla::dom