I noticed a few odd issue with thumbnail generation in FileBrowser and e.g. open/save dialogs.

Go to http://www.lunarpup.com/animations/animations.html and download 3-4 (or more) large GIFs, and place them into /home/anon

Open FileBrowser. Notice that sometimes you get a progress bar loading the images, but most of the time any interaction with the window while it generates causes it to hang.

Another odd issue: Open TextEditor (reboot if thumbnails already were generated), click the "Open" button. While the thumbnails are being generated, it is unresponsive. Now while it is not responsive, double click on README.md. Notice how TextEditor crashes:

TextEditor(25): FilePicker{0x020f0ff8}: Quit event loop with result 0
TextEditor(25): FilePicker{0x020f0ff8}: Event loop returned with result 0
USERSPACE(25) ASSERTION FAILED: false
../Libraries/LibIPC/Connection.h:221
[TextEditor(25:25)]: Terminating TextEditor(25) due to signal 6
[FinalizerTask(4:4)]: CPU[0] NP(error) fault at invalid address V0x00000004
[FinalizerTask(4:4)]: copy_from_user(0xc096e9ac, 0x00000004, 4) failed at V0x00000004
[FinalizerTask(4:4)]: 0xdeadc0de  Kernel::Processor::switch_context(Kernel::Thread*&, Kernel::Thread*&) +181
0xdeadc0de  Kernel::Scheduler::context_switch(Kernel::Thread*) +183
0xdeadc0de  Kernel::Scheduler::pick_next() +1683
0xdeadc0de  Kernel::Processor::check_invoke_scheduler() +125
0xdeadc0de  Kernel::Thread::die_if_needed() +157
0xdeadc0de  syscall_handler +1414
0xdeadc0de  syscall_asm_entry +49
0x081bf7f7  raise +22
0x080480bd  abort +13
0x081bac6c  tolower +0
0x08186e8f  IPC::ServerConnection<ProtocolClientEndpoint, ProtocolServerEndpoint>::ServerConnection(ProtocolClientEndpoint&, AK::StringView const&) +271
0x08184dfe  Protocol::Client::Client() +46
0x0805d3bf  Web::ResourceLoader::ResourceLoader() +61
0x0805d413  Web::ResourceLoader::the() +33
0x0805b1de  Web::ImageLoader::load(AK::URL const&) +176
0x080765bc  Web::HTML::HTMLImageElement::parse_attribute(AK::FlyString const&, AK::String const&) +66
0x08079f18  Web::HTML::HTMLDocumentParser::create_element_for(Web::HTML::HTMLToken const&) +210
0x0807be8c  Web::HTML::HTMLDocumentParser::insert_html_element(Web::HTML::HTMLToken const&) +38
0x08082d9f  Web::HTML::HTMLDocumentParser::handle_in_body(Web::HTML::HTMLToken&) +16041
0x0807dccc  Web::HTML::HTMLDocumentParser::run(AK::URL const&) +214
0x08054a10  Web::InProcessWebView::load_html(AK::StringView const&, AK::URL const&) +68
0x0804e9c3  TextEditorWidget::update_markdown_preview() +191
0x0804f727  TextEditorWidget::set_path(AK::LexicalPath const&) +353
0x0805355f  TextEditorWidget::open_sesame(AK::String const&) +357
0x0805379f  AK::Function<void (GUI::Action&)>::CallableWrapper<TextEditorWidget::TextEditorWidget()::{lambda(auto:1&)#16}>::call(GUI::Action&) const +231
0x080e4168  GUI::Action::activate(Core::Object*) +172
0x0812203f  GUI::AbstractButton::mouseup_event(GUI::MouseEvent&) +107
0x081b8ca8  Core::Object::dispatch_event(Core::Event&, Core::Object*) +74
0x0811aacc  GUI::Window::handle_mouse_event(GUI::MouseEvent&) +236
0x081b8ca8  Core::Object::dispatch_event(Core::Event&, Core::Object*) +74
0x081b107e  Core::EventLoop::pump(Core::EventLoop::WaitMode) +308
0x081b11fd  Core::EventLoop::exec() +43
0x0804878d  main +898
0x0804e23e  _start +94

[FinalizerTask(4:4)]: CPU[0] NP(error) fault at invalid address V0x00000004
[FinalizerTask(4:4)]: copy_from_user(0xc096e9ac, 0x00000004, 4) failed at V0x00000004
[FinalizerTask(4:4)]: 0xdeadc0de  Kernel::Processor::switch_context(Kernel::Thread*&, Kernel::Thread*&) +181
0xdeadc0de  Kernel::Scheduler::context_switch(Kernel::Thread*) +183
0xdeadc0de  Kernel::Scheduler::pick_next() +1683
0xdeadc0de  Kernel::Processor::check_invoke_scheduler() +125
0xdeadc0de  Kernel::ScopedSpinLock<Kernel::RecursiveSpinLock>::~ScopedSpinLock() +198
0xdeadc0de  Kernel::MemoryManager::handle_page_fault(Kernel::PageFault const&) +453
0xdeadc0de  page_fault_handler +254
0xdeadc0de  page_fault_asm_entry +38
0x081903cb  Gfx::load_gif_frame_descriptors(Gfx::GIFLoadingContext&) +1993
0x08190e3b  Gfx::GIFImageDecoderPlugin::frame(unsigned long) +51
0x08190f14  Gfx::GIFImageDecoderPlugin::bitmap() +44
0x08190fa7  Gfx::load_gif(AK::StringView const&) +73
0x0818ac5e  Gfx::Bitmap::load_from_file(AK::StringView const&) +272
0x080f7f24  AK::Function<AK::RefPtr<Gfx::Bitmap> ()>::CallableWrapper<GUI::FileSystemModel::fetch_thumbnail_for(GUI::FileSystemModel::Node const&)::{lambda()#1}>::call() const +46
0x080fa0c9  LibThread::BackgroundAction<AK::RefPtr<Gfx::Bitmap> >::BackgroundAction(AK::Function<AK::RefPtr<Gfx::Bitmap> ()>, AK::Function<void (AK::RefPtr<Gfx::Bitmap>)>)::{lambda()#1}::operator()() const +49
0x081337e0  background_thread_func() +378
0x08133a15  LibThread::Thread::start()::{lambda(void*)#1}::_FUN(void*) +37
0x08133c4f  pthread_create_helper +12

[FinalizerTask(4:4)]: Scheduler[0]: Reaped unparented process TextEditor(25), exit status: 6