Bug 1501748 - Make GeckoThread.waitOnGecko() time out by default. r=geckoview-reviewers,esawin

All of the current usage can survive a timeout, and we'd rather
that than a deadlock. Future code that does want to risk a
deadlock can call `GeckoThread.waitOnGeckoForever` instead.

Differential Revision: https://phabricator.services.mozilla.com/D14560

--HG--
extra : moz-landing-system : lando

mobile/android/geckoview/src/main/java/org/mozilla/gecko/GeckoThread.java

@@ -5,16 +5,13 @@
 
 package org.mozilla.gecko;
 
-import org.mozilla.gecko.TelemetryUtils;
 import org.mozilla.gecko.annotation.RobocopTarget;
 import org.mozilla.gecko.annotation.WrapForJNI;
 import org.mozilla.gecko.mozglue.GeckoLoader;
 import org.mozilla.gecko.process.GeckoProcessManager;
 import org.mozilla.gecko.util.GeckoBundle;
-import org.mozilla.gecko.util.FileUtils;
 import org.mozilla.gecko.util.ThreadUtils;
 import org.mozilla.geckoview.BuildConfig;
-import org.mozilla.geckoview.GeckoRuntimeSettings;
 
 import android.content.Context;
 import android.content.res.Configuration;
@@ -134,6 +131,8 @@ public class GeckoThread extends Thread {
     public static final int FLAG_PRELOAD_CHILD = 1 << 1; // Preload child during main thread start.
     public static final int FLAG_ENABLE_NATIVE_CRASHREPORTER = 1 << 2; // Enable native crash reporting
 
+    public static final long DEFAULT_TIMEOUT = 5000;
+
     /* package */ static final String EXTRA_ARGS = "args";
     private static final String EXTRA_PREFS_FD = "prefsFd";
     private static final String EXTRA_PREF_MAP_FD = "prefMapFd";
@@ -576,8 +575,21 @@ public class GeckoThread extends Thread {
                              "speculativeConnectNative", uri);
     }
 
-    @WrapForJNI @RobocopTarget
-    public static native void waitOnGecko();
+    @WrapForJNI(stubName = "WaitOnGecko")
+    @RobocopTarget
+    private static native boolean nativeWaitOnGecko(long timeoutMillis);
+
+    public static void waitOnGeckoForever() {
+        nativeWaitOnGecko(0);
+    }
+
+    public static boolean waitOnGecko() {
+        return waitOnGecko(DEFAULT_TIMEOUT);
+    }
+
+    public static boolean waitOnGecko(long timeoutMillis) {
+        return nativeWaitOnGecko(timeoutMillis);
+    }
 
     @WrapForJNI(stubName = "OnPause", dispatchTo = "gecko")
     private static native void nativeOnPause();

widget/android/nsAppShell.cpp

@@ -144,7 +144,7 @@ class GeckoThreadSupport final
     specConn->SpeculativeConnect2(uri, principal, nullptr);
   }
 
-  static void WaitOnGecko() {
+  static bool WaitOnGecko(int64_t timeoutMillis) {
     struct NoOpRunnable : Runnable {
       NoOpRunnable() : Runnable("NoOpRunnable") {}
       NS_IMETHOD Run() override { return NS_OK; }
@@ -160,7 +160,8 @@ class GeckoThreadSupport final
                                 NS_DISPATCH_SYNC);
       }
     };
-    nsAppShell::SyncRunEvent(NoOpEvent());
+    return nsAppShell::SyncRunEvent(
+        NoOpEvent(), nullptr, TimeDuration::FromMilliseconds(timeoutMillis));
   }
 
   static void OnPause() {
@@ -686,8 +687,9 @@ bool nsAppShell::ProcessNextNativeEvent(bool mayWait) {
   return true;
 }
 
-void nsAppShell::SyncRunEvent(
-    Event&& event, UniquePtr<Event> (*eventFactory)(UniquePtr<Event>&&)) {
+bool nsAppShell::SyncRunEvent(
+    Event&& event, UniquePtr<Event> (*eventFactory)(UniquePtr<Event>&&),
+    const TimeDuration timeout) {
   // Perform the call on the Gecko thread in a separate lambda, and wait
   // on the monitor on the current thread.
   MOZ_ASSERT(!NS_IsMainThread());
@@ -699,19 +701,20 @@ void nsAppShell::SyncRunEvent(
 
   if (MOZ_UNLIKELY(!appShell)) {
     // Post-shutdown.
-    return;
+    return false;
   }
 
   bool finished = false;
   auto runAndNotify = [&event, &finished] {
     nsAppShell* const appShell = nsAppShell::Get();
     if (MOZ_UNLIKELY(!appShell || appShell->mSyncRunQuit)) {
-      return;
+      return false;
     }
     event.Run();
     finished = true;
     mozilla::MutexAutoLock shellLock(*sAppShellLock);
     appShell->mSyncRunFinished.NotifyAll();
+    return finished;
   };
 
   UniquePtr<Event> runAndNotifyEvent =
@@ -725,8 +728,10 @@ void nsAppShell::SyncRunEvent(
   appShell->mEventQueue.Post(std::move(runAndNotifyEvent));
 
   while (!finished && MOZ_LIKELY(sAppShell && !sAppShell->mSyncRunQuit)) {
-    appShell->mSyncRunFinished.Wait();
+    appShell->mSyncRunFinished.Wait(timeout);
   }
+
+  return finished;
 }
 
 already_AddRefed<nsIURI> nsAppShell::ResolveURI(const nsCString& aUriStr) {

widget/android/nsAppShell.h

@@ -13,6 +13,7 @@
 #include "mozilla/Monitor.h"
 #include "mozilla/Move.h"
 #include "mozilla/StaticPtr.h"
+#include "mozilla/TimeStamp.h"  // for mozilla::TimeDuration
 #include "mozilla/TypeTraits.h"
 #include "mozilla/UniquePtr.h"
 #include "mozilla/Unused.h"
@@ -66,7 +67,7 @@ class nsAppShell : public nsBaseAppShell {
 
    public:
     explicit LambdaEvent(T&& l) : lambda(std::move(l)) {}
-    void Run() override { return lambda(); }
+    void Run() override { lambda(); }
   };
 
   class ProxyEvent : public Event {
@@ -123,9 +124,11 @@ class nsAppShell : public nsBaseAppShell {
   }
 
   // Post a event and wait for it to finish running on the Gecko thread.
-  static void SyncRunEvent(Event&& event,
-                           mozilla::UniquePtr<Event> (*eventFactory)(
-                               mozilla::UniquePtr<Event>&&) = nullptr);
+  static bool SyncRunEvent(
+      Event&& event,
+      mozilla::UniquePtr<Event> (*eventFactory)(mozilla::UniquePtr<Event>&&) =
+          nullptr,
+      const mozilla::TimeDuration timeout = mozilla::TimeDuration::Forever());
 
   template <typename T>
   static typename mozilla::EnableIf<!mozilla::IsBaseOf<Event, T>::value,