Bug 855276: Add assertions to catch the cause. r=bent

dom/indexedDB/TransactionThreadPool.cpp

@@ -16,6 +16,11 @@
 
 using mozilla::MonitorAutoLock;
 
+#define MOZ_OPT_ASSERT(cond) \
+  if (!(cond)) {             \
+    MOZ_CRASH();             \
+  }
+
 USING_INDEXEDDB_NAMESPACE
 
 namespace {
@@ -48,6 +53,7 @@ private:
 END_INDEXEDDB_NAMESPACE
 
 TransactionThreadPool::TransactionThreadPool()
+  : mTouchingCallbacks(false)
 {
   NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
   NS_ASSERTION(!gInstance, "More than one instance!");
@@ -140,11 +146,14 @@ TransactionThreadPool::Cleanup()
   NS_ENSURE_SUCCESS(rv, rv);
 
   if (!mCompleteCallbacks.IsEmpty()) {
+    MOZ_OPT_ASSERT(!mTouchingCallbacks);
+    mTouchingCallbacks = true;
     // Run all callbacks manually now.
     for (uint32_t index = 0; index < mCompleteCallbacks.Length(); index++) {
       mCompleteCallbacks[index].mCallback->Run();
     }
     mCompleteCallbacks.Clear();
+    mTouchingCallbacks = false;
 
     // And make sure they get processed.
     rv = NS_ProcessPendingEvents(nullptr);
@@ -216,6 +225,8 @@ TransactionThreadPool::FinishTransaction(IDBTransaction* aTransaction)
 
     // See if we need to fire any complete callbacks.
     uint32_t index = 0;
+    MOZ_OPT_ASSERT(!mTouchingCallbacks);
+    mTouchingCallbacks = true;
     while (index < mCompleteCallbacks.Length()) {
       if (MaybeFireCallback(mCompleteCallbacks[index])) {
         mCompleteCallbacks.RemoveElementAt(index);
@@ -224,6 +235,7 @@ TransactionThreadPool::FinishTransaction(IDBTransaction* aTransaction)
         index++;
       }
     }
+    mTouchingCallbacks = false;
 
     return;
   }
@@ -360,6 +372,8 @@ TransactionThreadPool::WaitForDatabasesToComplete(
   NS_ASSERTION(!aDatabases.IsEmpty(), "No databases to wait on!");
   NS_ASSERTION(aCallback, "Null pointer!");
 
+  MOZ_OPT_ASSERT(!mTouchingCallbacks);
+  mTouchingCallbacks = true;
   DatabasesCompleteCallback* callback = mCompleteCallbacks.AppendElement();
 
   callback->mCallback = aCallback;
@@ -368,6 +382,8 @@ TransactionThreadPool::WaitForDatabasesToComplete(
   if (MaybeFireCallback(*callback)) {
     mCompleteCallbacks.RemoveElementAt(mCompleteCallbacks.Length() - 1);
   }
+
+  mTouchingCallbacks = false;
 }
 
 // static

dom/indexedDB/TransactionThreadPool.h

@@ -181,6 +181,7 @@ protected:
     mTransactionsInProgress;
 
   nsTArray<DatabasesCompleteCallback> mCompleteCallbacks;
+  bool mTouchingCallbacks;
 };
 
 END_INDEXEDDB_NAMESPACE