Bug 1155547 - Wait Nuwa forking a process if preallocated process isn't present. r=khuey

dom/base/nsFrameLoader.cpp

@@ -2276,7 +2276,12 @@ nsFrameLoader::TryRemoteBrowser()
   NS_ENSURE_TRUE(rv, false);
 
   nsCOMPtr<Element> ownerElement = mOwnerContent;
-  mRemoteBrowser = ContentParent::CreateBrowserOrApp(context, ownerElement, openerContentParent);
+  TabParent* browser = ContentParent::CreateBrowserOrApp(context, ownerElement, openerContentParent);
+  if (mRemoteBrowser) {
+    MOZ_ASSERT(mRemoteBrowser == browser, "Must be the same as that obtained from another call");
+    return false;
+  }
+  mRemoteBrowser = browser;
   if (!mRemoteBrowser) {
     return false;
   }

dom/ipc/ContentParent.cpp

@@ -703,7 +703,22 @@ ContentParent::GetNewOrPreallocatedAppProcess(mozIApplication* aApp,
                                               /*out*/ bool* aTookPreAllocated)
 {
     MOZ_ASSERT(aApp);
+#ifdef MOZ_NUWA_PROCESS
+    nsRefPtr<ContentParent> process;
+    {
+        nsAutoString manifestURL;
+        if (NS_FAILED(aApp->GetManifestURL(manifestURL))) {
+            NS_ERROR("Failed to get manifest URL");
+            return nullptr;
+        }
+        process = PreallocatedProcessManager::BlockForNewProcess(manifestURL);
+        if (!process) {
+            process = sAppContentParents->Get(manifestURL);
+        }
+    }
+#else
     nsRefPtr<ContentParent> process = PreallocatedProcessManager::Take();
+#endif
 
     if (process) {
         if (!process->SetPriorityAndCheckIsAlive(aInitialPriority)) {
@@ -871,7 +886,11 @@ ContentParent::GetNewOrUsedBrowserProcess(bool aForBrowserElement,
     }
 
     // Try to take and transform the preallocated process into browser.
+#ifdef MOZ_NUWA_PROCESS
+    nsRefPtr<ContentParent> p = PreallocatedProcessManager::BlockForNewProcess(NS_LITERAL_STRING(""));
+#else
     nsRefPtr<ContentParent> p = PreallocatedProcessManager::Take();
+#endif
     if (p) {
         p->TransformPreallocatedIntoBrowser(aOpener);
     } else {

dom/ipc/PreallocatedProcessManager.cpp

@@ -59,6 +59,7 @@ public:
   void OnNuwaReady();
   bool PreallocatedProcessReady();
   already_AddRefed<ContentParent> GetSpareProcess();
+  already_AddRefed<ContentParent> BlockForNewProcess(const nsAString& aManifestURL);
 
 private:
   void NuwaFork();
@@ -72,6 +73,7 @@ private:
 
   // Nuwa process is ready for creating new process.
   bool mIsNuwaReady;
+  nsTArray<nsString> mWaitingList;
 #endif
 
 private:
@@ -283,6 +285,44 @@ PreallocatedProcessManagerImpl::GetSpareProcess()
   return process.forget();
 }
 
+already_AddRefed<ContentParent>
+PreallocatedProcessManagerImpl::BlockForNewProcess(const nsAString& aManifestURL)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+  if (!mEnabled || !IsNuwaReady()) {
+    // If nuwa is not ready, we can't enter the nested loop.
+    return nullptr;
+  }
+
+  if (mSpareProcesses.IsEmpty()) {
+    // a request comes in while there's no preallocated process. fork now.
+    if (aManifestURL.Length() == 0) {
+      // for browser.
+      NuwaFork();
+    } else if (mWaitingList.IndexOf(aManifestURL) == nsTArray<nsString>::NoIndex) {
+      // add the manifest url to waiting list. if there's another request came in while
+      // we are in nested loop, this will prevent later request from forking again.
+      NuwaFork();
+      mWaitingList.AppendElement(aManifestURL);
+    }
+    while (mSpareProcesses.IsEmpty() &&
+           (aManifestURL.Length() != 0 &&
+            mWaitingList.IndexOf(aManifestURL) != nsTArray<nsString>::NoIndex)) {
+      NS_ProcessNextEvent();
+    }
+    // If we are no longer in the waiting list, just return and content parent will
+    // get a process for us.
+    if (aManifestURL.Length() != 0 &&
+        mWaitingList.IndexOf(aManifestURL) == nsTArray<nsString>::NoIndex) {
+      return nullptr;
+    }
+    mWaitingList.RemoveElement(aManifestURL);
+  }
+
+  return GetSpareProcess();
+}
+
+
 /**
  * Publish a ContentParent to spare process list.
  */
@@ -484,6 +524,12 @@ PreallocatedProcessManager::PreallocatedProcessReady()
   return GetPPMImpl()->PreallocatedProcessReady();
 }
 
+/* static */ already_AddRefed<ContentParent>
+PreallocatedProcessManager::BlockForNewProcess(const nsAString& aManifestURL)
+{
+  return GetPPMImpl()->BlockForNewProcess(aManifestURL);
+}
+
 #endif
 
 } // namespace mozilla

dom/ipc/PreallocatedProcessManager.h

@@ -84,6 +84,7 @@ public:
   static bool IsNuwaReady();
   static void OnNuwaReady();
   static bool PreallocatedProcessReady();
+  static already_AddRefed<ContentParent> BlockForNewProcess(const nsAString& aManifestURL);
 #endif
 
 private: