[core] Allow pausing RunLoopsupstream/prioritize-thread-pause-resume

Previously we had the capability to pause on the Thread object, which used regular tasks to pause the RunLoop by blocking it. Instead, we can now pause the entire RunLoop and prevent it from processing items. This means that a pause() call is no longer treated as a regular task. Instead, it will take precedence over scheduled tasks, which means that a pause() call takes effect much more instantly since the RunLoop doesn't process the queue before the pause() task. Having pause() take effect much quicker is useful for situations where stopping the loop quickly is important, e.g. when the application goes to the background on iOS, and we have to stop processing tasks that access the file system. It also reduces the length of the blocking pause() call since the time until the RunLoop is paused is shortened.

1 files changed, 54 insertions, 0 deletions

diff --git a/test/util/thread.test.cpp b/test/util/thread.test.cpp
index 76fb5ce3f0..c74dae2ec6 100644
--- a/test/util/thread.test.cpp
+++ b/test/util/thread.test.cpp
@@ -275,3 +275,57 @@ TEST(Thread, PauseResume) {
     thread.actor().invoke(&TestWorker::send, [&] { loop.stop(); });
     loop.run();
 }
+
+TEST(Thread, MultiplePauseResumeCalls) {
+    RunLoop loop;
+
+    Thread<TestWorker> thread("Test");
+
+    // Test if multiple pause calls work
+    thread.pause();
+    thread.pause();
+    thread.resume();
+    thread.resume();
+
+    thread.actor().invoke(&TestWorker::send, [&] { loop.stop(); });
+    loop.run();
+}
+
+TEST(Thread, TestImmediatePause) {
+    using namespace std::chrono_literals;
+
+    RunLoop loop;
+
+    Thread<TestWorker> thread("Test");
+
+    std::promise<void> resume;
+    auto resumed = resume.get_future();
+
+    std::atomic<bool> ending { false };
+
+    thread.pause();
+    thread.actor().invoke(&TestWorker::send, [&] {
+        resume.set_value();
+
+        // Make sure we have some time to process the pause() call.
+        std::this_thread::sleep_for(300ms);
+    });
+
+    // We're scheduling a second action right after, before calling pause. Ensure that it never
+    // gets called.
+    thread.actor().invoke(&TestWorker::send, [&] {
+        EXPECT_TRUE(ending) << "callback called without ending";
+    });
+
+    thread.resume();
+    resumed.get();
+    thread.pause();
+
+    Timer timer;
+    timer.start(600ms, Duration::zero(), [&] {
+        ending = true;
+        loop.stop();
+    });
+
+    loop.run();
+}