Merge lp:~kdub/mir/fix-silo0-1480418 into lp:~mir-team/mir/silo0

[Kevin DuBois]

When creating compositing threads, add the observer only after we're ready to service scheduling requests. Silo0's USC was resizing surfaces as a result of DisplayListerner::add_display, which would deadlock on schedule_frames. (essentially, a callback-with-held lock problem)

fixes: lp: #1481418

When creating compositing threads, add the observer only after we're ready to service scheduling requests. Silo0's USC was resizing surfaces as a result of DisplayListerner::add_display, which would deadlock on schedule_frames. (essentially, a callback-with-held lock problem)

fixes: lp: #1481418

=== modified file 'src/server/compositor/multi_threaded_compositor.cpp'
--- src/server/compositor/multi_threaded_compositor.cpp	2015-06-17 05:20:42 +0000
+++ src/server/compositor/multi_threaded_compositor.cpp	2015-08-04 17:13:45 +0000
@@ -300,12 +300,12 @@
             destroy_compositing_threads(lk);
         }};
 
+    create_compositing_threads();
+
     lk.unlock();
     scene->add_observer(observer);
     lk.lock();
 
-    create_compositing_threads();
-
     /* Optional first render */
     if (compose_on_start)
     {

=== modified file 'tests/unit-tests/compositor/test_multi_threaded_compositor.cpp'
--- tests/unit-tests/compositor/test_multi_threaded_compositor.cpp	2015-06-17 05:20:42 +0000
+++ tests/unit-tests/compositor/test_multi_threaded_compositor.cpp	2015-08-04 17:13:45 +0000
@@ -847,3 +847,40 @@
 
     compositor.start();
 }
+
+//LP: 1481418
+TEST(MultiThreadedCompositor, can_schedule_from_display_observer_when_adding_display)
+{
+    using namespace testing;
+    unsigned int const nbuffers{3};
+    auto display = std::make_shared<StubDisplayWithMockBuffers>(nbuffers);
+    auto stub_scene = std::make_shared<NiceMock<StubScene>>();
+    auto mock_display_listener = std::make_shared<NiceMock<MockDisplayListener>>();
+    auto db_compositor_factory = std::make_shared<mtd::NullDisplayBufferCompositorFactory>();
+    auto mock_report = std::make_shared<testing::NiceMock<mtd::MockCompositorReport>>();
+
+    ON_CALL(*mock_display_listener, add_display(_))
+        .WillByDefault(InvokeWithoutArgs([&]{ stub_scene->emit_change_event(); }));
+
+    mc::MultiThreadedCompositor compositor{
+        display, stub_scene, db_compositor_factory, mock_display_listener, mock_report, true};
+    compositor.start();
+}
+
+TEST(MultiThreadedCompositor, can_schedule_from_display_observer_when_removing_display)
+{
+    using namespace testing;
+    unsigned int const nbuffers{3};
+    auto display = std::make_shared<StubDisplayWithMockBuffers>(nbuffers);
+    auto stub_scene = std::make_shared<NiceMock<StubScene>>();
+    auto mock_display_listener = std::make_shared<NiceMock<MockDisplayListener>>();
+    auto db_compositor_factory = std::make_shared<mtd::NullDisplayBufferCompositorFactory>();
+    auto mock_report = std::make_shared<testing::NiceMock<mtd::MockCompositorReport>>();
+
+    ON_CALL(*mock_display_listener, remove_display(_))
+        .WillByDefault(InvokeWithoutArgs([&]{ stub_scene->emit_change_event(); }));
+
+    mc::MultiThreadedCompositor compositor{
+        display, stub_scene, db_compositor_factory, mock_display_listener, mock_report, true};
+    compositor.start();
+}