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diff --git a/toolkit/components/osfile/tests/xpcshell/test_osfile_kill.js b/toolkit/components/osfile/tests/xpcshell/test_osfile_kill.js
new file mode 100644
index 000000000..e32c37224
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+++ b/toolkit/components/osfile/tests/xpcshell/test_osfile_kill.js
@@ -0,0 +1,100 @@
+"use strict";
+
+Components.utils.import("resource://gre/modules/osfile.jsm");
+
+// We want the actual global to get at the internals since Scheduler is not
+// exported.
+var AsyncFrontGlobal = Components.utils.import(
+                         "resource://gre/modules/osfile/osfile_async_front.jsm",
+                          null);
+var Scheduler = AsyncFrontGlobal.Scheduler;
+
+/**
+ * Verify that Scheduler.kill() interacts with other OS.File requests correctly,
+ * and that no requests are lost.  This is relevant because on B2G we
+ * auto-kill the worker periodically, making it very possible for valid requests
+ * to be interleaved with the automatic kill().
+ *
+ * This test is being created with the fix for Bug 1125989 where `kill` queue
+ * management was found to be buggy.  It is a glass-box test that explicitly
+ * re-creates the observed failure situation; it is not guaranteed to prevent
+ * all future regressions.  The following is a detailed explanation of the test
+ * for your benefit if this test ever breaks or you are wondering what was the
+ * point of all this.  You might want to skim the code below first.
+ *
+ * OS.File maintains a `queue` of operations to be performed.  This queue is
+ * nominally implemented as a chain of promises.  Every time a new job is
+ * OS.File.push()ed, it effectively becomes the new `queue` promise.  (An
+ * extra promise is interposed with a rejection handler to avoid the rejection
+ * cascading, but that does not matter for our purposes.)
+ *
+ * The flaw in `kill` was that it would wait for the `queue` to complete before
+ * replacing `queue`.  As a result, another OS.File operation could use `push`
+ * (by way of OS.File.post()) to also use .then() on the same `queue` promise.
+ * Accordingly, assuming that promise was not yet resolved (due to a pending
+ * OS.File request), when it was resolved, both the task scheduled in `kill`
+ * and in `post` would be triggered.  Both of those tasks would run until
+ * encountering a call to worker.post().
+ *
+ * Re-creating this race is not entirely trivial because of the large number of
+ * promises used by the code causing control flow to repeatedly be deferred.  In
+ * a slightly simpler world we could run the follwing in the same turn of the
+ * event loop and trigger the problem.
+ * - any OS.File request
+ * - Scheduler.kill()
+ * - any OS.File request
+ *
+ * However, we need the Scheduler.kill task to reach the point where it is
+ * waiting on the same `queue` that another task has been scheduled against.
+ * Since the `kill` task yields on the `killQueue` promise prior to yielding
+ * on `queue`, however, some turns of the event loop are required.  Happily,
+ * for us, as discussed above, the problem triggers when we have two promises
+ * scheduled on the `queue`, so we can just wait to schedule the second OS.File
+ * request on the queue.  (Note that because of the additional then() added to
+ * eat rejections, there is an important difference between the value of
+ * `queue` and the value returned by the first OS.File request.)
+ */
+add_task(function* test_kill_race() {
+  // Ensure the worker has been created and that SET_DEBUG has taken effect.
+  // We have chosen OS.File.exists for our tests because it does not trigger
+  // a rejection and we absolutely do not care what the operation is other
+  // than it does not invoke a native fast-path.
+  yield OS.File.exists('foo.foo');
+
+  do_print('issuing first request');
+  let firstRequest = OS.File.exists('foo.bar');
+  let secondRequest;
+  let secondResolved = false;
+
+  // As noted in our big block comment, we want to wait to schedule the
+  // second request so that it races `kill`'s call to `worker.post`.  Having
+  // ourselves wait on the same promise, `queue`, and registering ourselves
+  // before we issue the kill request means we will get run before the `kill`
+  // task resumes and allow us to precisely create the desired race.
+  Scheduler.queue.then(function() {
+    do_print('issuing second request');
+    secondRequest = OS.File.exists('foo.baz');
+    secondRequest.then(function() {
+      secondResolved = true;
+    });
+  });
+
+  do_print('issuing kill request');
+  let killRequest = Scheduler.kill({ reset: true, shutdown: false });
+
+  // Wait on the killRequest so that we can schedule a new OS.File request
+  // after it completes...
+  yield killRequest;
+  // ...because our ordering guarantee ensures that there is at most one
+  // worker (and this usage here should not be vulnerable even with the
+  // bug present), so when this completes the secondRequest has either been
+  // resolved or lost.
+  yield OS.File.exists('foo.goz');
+
+  ok(secondResolved,
+     'The second request was resolved so we avoided the bug. Victory!');
+});
+
+function run_test() {
+  run_next_test();
+}