1 files changed, 102 insertions, 0 deletions
diff --git a/toolkit/components/telemetry/tests/unit/test_ThreadHangStats.js b/toolkit/components/telemetry/tests/unit/test_ThreadHangStats.js
new file mode 100644
index 000000000..e8c9f868a
--- /dev/null
+++ b/toolkit/components/telemetry/tests/unit/test_ThreadHangStats.js
@@ -0,0 +1,102 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+Cu.import("resource://gre/modules/Services.jsm");
+
+function getMainThreadHangStats() {
+  let threads = Services.telemetry.threadHangStats;
+  return threads.find((thread) => (thread.name === "Gecko"));
+}
+
+function run_test() {
+  let startHangs = getMainThreadHangStats();
+
+  // We disable hang reporting in several situations (e.g. debug builds,
+  // official releases). In those cases, we don't have hang stats available
+  // and should exit the test early.
+  if (!startHangs) {
+    ok("Hang reporting not enabled.");
+    return;
+  }
+
+  if (Services.appinfo.OS === 'Linux' || Services.appinfo.OS === 'Android') {
+    // We use the rt_tgsigqueueinfo syscall on Linux which requires a
+    // certain kernel version. It's not an error if the system running
+    // the test is older than that.
+    let kernel = Services.sysinfo.get('kernel_version') ||
+                 Services.sysinfo.get('version');
+    if (Services.vc.compare(kernel, '2.6.31') < 0) {
+      ok("Hang reporting not supported for old kernel.");
+      return;
+    }
+  }
+
+  // Run three events in the event loop:
+  // the first event causes a transient hang;
+  // the second event causes a permanent hang;
+  // the third event checks results from previous events.
+
+  do_execute_soon(() => {
+    // Cause a hang lasting 1 second (transient hang).
+    let startTime = Date.now();
+    while ((Date.now() - startTime) < 1000);
+  });
+
+  do_execute_soon(() => {
+    // Cause a hang lasting 10 seconds (permanent hang).
+    let startTime = Date.now();
+    while ((Date.now() - startTime) < 10000);
+  });
+
+  do_execute_soon(() => {
+    do_test_pending();
+
+    let check_results = () => {
+      let endHangs = getMainThreadHangStats();
+
+      // Because hangs are recorded asynchronously, if we don't see new hangs,
+      // we should wait for pending hangs to be recorded. On the other hand,
+      // if hang monitoring is broken, this test will time out.
+      if (endHangs.hangs.length === startHangs.hangs.length) {
+        do_timeout(100, check_results);
+        return;
+      }
+
+      let check_histogram = (histogram) => {
+        equal(typeof histogram, "object");
+        equal(histogram.histogram_type, 0);
+        equal(typeof histogram.min, "number");
+        equal(typeof histogram.max, "number");
+        equal(typeof histogram.sum, "number");
+        ok(Array.isArray(histogram.ranges));
+        ok(Array.isArray(histogram.counts));
+        equal(histogram.counts.length, histogram.ranges.length);
+      };
+
+      // Make sure the hang stats structure is what we expect.
+      equal(typeof endHangs, "object");
+      check_histogram(endHangs.activity);
+
+      ok(Array.isArray(endHangs.hangs));
+      notEqual(endHangs.hangs.length, 0);
+
+      ok(Array.isArray(endHangs.hangs[0].stack));
+      notEqual(endHangs.hangs[0].stack.length, 0);
+      equal(typeof endHangs.hangs[0].stack[0], "string");
+
+      // Make sure one of the hangs is a permanent
+      // hang containing a native stack.
+      ok(endHangs.hangs.some((hang) => (
+        Array.isArray(hang.nativeStack) &&
+        hang.nativeStack.length !== 0 &&
+        typeof hang.nativeStack[0] === "string"
+      )));
+
+      check_histogram(endHangs.hangs[0].histogram);
+
+      do_test_finished();
+    };
+
+    check_results();
+  });
+}