Bug 998330 - MinimizeMemory should happen on the opener thread, not on main-thread. r=asuth

storage/src/mozStorageConnection.cpp

@@ -51,6 +51,19 @@
 PRLogModuleInfo* gStorageLog = nullptr;
 #endif
 
+// Checks that the protected code is running on the main-thread only if the
+// connection was also opened on it.
+#ifdef DEBUG
+#define CHECK_MAINTHREAD_ABUSE() \
+  do { \
+    nsCOMPtr<nsIThread> mainThread = do_GetMainThread(); \
+    NS_WARN_IF_FALSE(threadOpenedOn == mainThread || !NS_IsMainThread(), \
+               "Using Storage synchronous API on main-thread, but the connection was opened on another thread."); \
+  } while(0)
+#else
+#define CHECK_MAINTHREAD_ABUSE() do { /* Nothing */ } while(0)
+#endif
+
 namespace mozilla {
 namespace storage {
 
@@ -1422,6 +1435,7 @@ Connection::CreateAsyncStatement(const nsACString &aSQLStatement,
 NS_IMETHODIMP
 Connection::ExecuteSimpleSQL(const nsACString &aSQLStatement)
 {
+  CHECK_MAINTHREAD_ABUSE();
   if (!mDBConn) return NS_ERROR_NOT_INITIALIZED;
 
   int srv = executeSql(mDBConn, PromiseFlatCString(aSQLStatement).get());

storage/src/mozStorageService.cpp

@@ -347,22 +347,32 @@ Service::minimizeMemory()
 
   for (uint32_t i = 0; i < connections.Length(); i++) {
     nsRefPtr<Connection> conn = connections[i];
-    if (conn->connectionReady()) {
-      NS_NAMED_LITERAL_CSTRING(shrinkPragma, "PRAGMA shrink_memory");
-      nsCOMPtr<mozIStorageConnection> syncConn = do_QueryInterface(
-        NS_ISUPPORTS_CAST(mozIStorageAsyncConnection*, conn));
-      DebugOnly<nsresult> rv;
+    if (!conn->connectionReady())
+      continue;
 
-      if (!syncConn) {
-        nsCOMPtr<mozIStoragePendingStatement> ps;
-        rv = connections[i]->ExecuteSimpleSQLAsync(shrinkPragma, nullptr,
-          getter_AddRefs(ps));
-      } else {
-        rv = connections[i]->ExecuteSimpleSQL(shrinkPragma);
-      }
+    NS_NAMED_LITERAL_CSTRING(shrinkPragma, "PRAGMA shrink_memory");
+    nsCOMPtr<mozIStorageConnection> syncConn = do_QueryInterface(
+      NS_ISUPPORTS_CAST(mozIStorageAsyncConnection*, conn));
+    bool onOpenedThread = false;
 
-      MOZ_ASSERT(NS_SUCCEEDED(rv),
-        "Should have been able to purge sqlite caches");
+    if (!syncConn) {
+      // This is a mozIStorageAsyncConnection, it can only be used on the main
+      // thread, so we can do a straight API call.
+      nsCOMPtr<mozIStoragePendingStatement> ps;
+      DebugOnly<nsresult> rv =
+        conn->ExecuteSimpleSQLAsync(shrinkPragma, nullptr, getter_AddRefs(ps));
+      MOZ_ASSERT(NS_SUCCEEDED(rv), "Should have purged sqlite caches");
+    } else if (NS_SUCCEEDED(conn->threadOpenedOn->IsOnCurrentThread(&onOpenedThread)) &&
+               onOpenedThread) {
+      // We are on the opener thread, so we can just proceed.
+      conn->ExecuteSimpleSQL(shrinkPragma);
+    } else {
+      // We are on the wrong thread, the query should be executed on the
+      // opener thread, so we must dispatch to it.
+      nsCOMPtr<nsIRunnable> event =
+        NS_NewRunnableMethodWithArg<const nsCString>(
+          conn, &Connection::ExecuteSimpleSQL, shrinkPragma);
+      conn->threadOpenedOn->Dispatch(event, NS_DISPATCH_NORMAL);
     }
   }
 }