1 files changed, 123 insertions, 0 deletions
diff --git a/dom/indexedDB/test/unit/test_writer_starvation.js b/dom/indexedDB/test/unit/test_writer_starvation.js
new file mode 100644
index 0000000000..c6fb485891
--- /dev/null
+++ b/dom/indexedDB/test/unit/test_writer_starvation.js
@@ -0,0 +1,123 @@
+/**
+ * Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ */
+/* eslint-disable mozilla/no-arbitrary-setTimeout */
+
+if (!this.window) {
+  this.runTest = function() {
+    todo(false, "Test disabled in xpcshell test suite for now");
+    finishTest();
+  };
+}
+
+var testGenerator = testSteps();
+
+function* testSteps() {
+  const name = this.window ? window.location.pathname : "Splendid Test";
+
+  // Needs to be enough to saturate the thread pool.
+  const SYNC_REQUEST_COUNT = 25;
+
+  let request = indexedDB.open(name, 1);
+  request.onerror = errorHandler;
+  request.onupgradeneeded = grabEventAndContinueHandler;
+  request.onsuccess = grabEventAndContinueHandler;
+  let event = yield undefined;
+
+  let db = event.target.result;
+  db.onerror = errorHandler;
+
+  is(event.target.transaction.mode, "versionchange", "Correct mode");
+
+  let objectStore = db.createObjectStore("foo", { autoIncrement: true });
+
+  request = objectStore.add({});
+  request.onerror = errorHandler;
+  request.onsuccess = grabEventAndContinueHandler;
+  event = yield undefined;
+
+  let key = event.target.result;
+  ok(key, "Got a key");
+
+  yield undefined;
+
+  let continueReading = true;
+  let readerCount = 0;
+  let writerCount = 0;
+  let callbackCount = 0;
+
+  // Generate a bunch of reads right away without returning to the event
+  // loop.
+  info("Generating " + SYNC_REQUEST_COUNT + " readonly requests");
+
+  for (let i = 0; i < SYNC_REQUEST_COUNT; i++) {
+    readerCount++;
+    let request = db
+      .transaction("foo")
+      .objectStore("foo")
+      .get(key);
+    request.onsuccess = function(event) {
+      is(event.target.transaction.mode, "readonly", "Correct mode");
+      callbackCount++;
+    };
+  }
+
+  while (continueReading) {
+    readerCount++;
+    info("Generating additional readonly request (" + readerCount + ")");
+    let request = db
+      .transaction("foo")
+      .objectStore("foo")
+      .get(key);
+    request.onsuccess = function(event) {
+      callbackCount++;
+      info("Received readonly request callback (" + callbackCount + ")");
+      is(event.target.transaction.mode, "readonly", "Correct mode");
+      if (callbackCount == SYNC_REQUEST_COUNT) {
+        writerCount++;
+        info(
+          "Generating 1 readwrite request with " +
+            readerCount +
+            " previous readonly requests"
+        );
+        let request = db
+          .transaction("foo", "readwrite")
+          .objectStore("foo")
+          .add({}, readerCount);
+        request.onsuccess = function(event) {
+          callbackCount++;
+          info("Received readwrite request callback (" + callbackCount + ")");
+          is(event.target.transaction.mode, "readwrite", "Correct mode");
+          is(
+            event.target.result,
+            callbackCount,
+            "write callback came before later reads"
+          );
+        };
+      } else if (callbackCount == SYNC_REQUEST_COUNT + 5) {
+        continueReading = false;
+      }
+    };
+
+    setTimeout(
+      function() {
+        testGenerator.next();
+      },
+      writerCount ? 1000 : 100
+    );
+    yield undefined;
+  }
+
+  while (callbackCount < readerCount + writerCount) {
+    executeSoon(function() {
+      testGenerator.next();
+    });
+    yield undefined;
+  }
+
+  is(callbackCount, readerCount + writerCount, "All requests accounted for");
+
+  finishTest();
+  yield undefined;
+}