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Zaggy1024 dcfec8bfbe LibC: Expect mutexes to be locked and needing wake when calling futex() 
tl;dr: This fixes deadlocks that would occur in most applications in
Serenity when SMP was enabled.

As an optimization to `pthread_mutex_unlock()`, if only one thread
holds a mutex lock, it will avoid calling `futex()` to wake, since no
threads are actually waiting in `futex()`.

If a thread manages to synchronously unlock and relock the same mutex,
the state will be set to indicate that a wake is not needed, regardless
of whether any other threads are waiting for the lock. This should be
fine, as a thread that is waiting will set the mutex to needing a wake
and check if it is unlocked to unblock itself in the same atomic
operation.

However, when `pthread_mutex_lock()` was called with only one thread
holding the mutex lock, instead of telling `futex()` to atomically
sleep the thread if the state is set to indicate that a wake is
needed, the first wait would check if the state was set to indicate a
wake was _not_ needed. This means it is possible for the call to
`futex()` to wait when any subsequent call to `pthread_mutex_unlock()`
would not call `futex()` to wake, causing it to wait forever.

After that, any other thread that tries to take the lock will see that
the lock is taken and also `futex()` wait. Despite the fact that these
other threads would set the state to needing a wake, there will be no
unblocked thread holding the lock to actually wake them.

By making it wait only if the state indicates to other threads that a
wake is needed, heavily contended mutexes should no longer cause
deadlocks. Most applications would encounter these deadlocks due to the
mutex used by `malloc()`, some sooner than others. The worst offenders
(other than Ladybird) were most likely VideoPlayer and SoundPlayer.
2023-08-09 05:31:35 +02:00
.devcontainer Meta: Switch to clang-format-16 as the standard formatter 2023-07-08 10:32:56 +01:00
.github CI: Restore running test262 and Wasm tests 2023-08-08 10:59:41 -04:00
AK AK: Remove the API to explicitly construct short strings 2023-08-08 07:37:21 +02:00
Base Base+LibCards: Add basic set of playing card backs 2023-08-08 14:56:25 +01:00
Documentation Documentation: Add instructions to disable OpenSSL legacy renegotiation 2023-08-07 11:14:34 -06:00
Kernel Kernel/VFS: Ensure working with mount entry per a custody is safe 2023-08-05 18:41:01 +02:00
Ladybird Ladybird: Add the select-all action to the JS console 2023-08-09 05:13:24 +02:00
Meta LibJS: Rip out the AST interpreter :^) 2023-08-08 13:07:13 +02:00
Ports Ports: Remove the filename entry from files 2023-08-08 19:57:43 +02:00
Tests LibWeb: Add namespaces to Universal and TagName selectors 2023-08-08 20:49:45 +01:00
Toolchain Toolchain: Enable Objective-C and Objective-C++ 2023-07-29 16:52:11 -06:00
Userland LibC: Expect mutexes to be locked and needing wake when calling futex() 2023-08-09 05:31:35 +02:00
.clang-format Everywhere: Remove needless trailing semi-colons after functions 2023-07-08 10:32:56 +01:00
.clang-tidy Meta: Disable the misc-no-recursion check in clang-tidy 2023-03-18 16:34:41 +01:00
.editorconfig Meta: Add .editorconfig 2022-09-10 17:32:55 +01:00
.gitattributes Repository: Protect port patches from CRLF/LF normalization 2022-01-12 01:08:38 +01:00
.gitignore Meta: Remove .gitignore from Base/ 2023-08-04 13:15:24 +02:00
.gn Meta: Add the start of a gn build based on the LLVM gn build 2023-07-09 16:22:58 -06:00
.mailmap Everywhere: Update copyrights with my new serenityos.org e-mail :^) 2023-07-15 16:21:29 +02:00
.pre-commit-config.yaml Meta: Add a post-commit commit message linter hook 2021-05-02 16:28:01 +02:00
.prettierignore LibJS: Add DisposableStack{, Prototype, Constructor} 2023-01-23 09:56:50 +00:00
.prettierrc Meta: Move prettier config files to the root of the repository 2020-08-24 18:21:33 +02:00
.ycm_extra_conf.py Meta: Remove i686 references in YCM configuration 2022-12-28 11:53:41 +01:00
azure-pipelines.yml CI: Remove extraneous toolchain job from Azure CI 2022-12-28 15:26:12 -05:00
CMakeLists.txt Toolchain+Ports: Update LLVM to 16.0.6 2023-06-27 12:40:38 +02:00
CONTRIBUTING.md Meta: Update maintainer section in CONTRIBUTING.md 2023-08-04 12:37:44 +02:00
LICENSE Meta: Update the year range in LICENSE :^) 2023-01-01 09:38:07 +00:00
README.md Meta: Add Tim Ledbetter to the contributors list :^) 2023-08-07 12:38:03 +02:00
SECURITY.md Meta: Add a security policy 2022-06-29 03:29:27 +00:00

README.md

SerenityOS

Graphical Unix-like operating system for x86-64 computers.

GitHub Actions Status Azure DevOps Status Fuzzing Status Sonar Cube Static Analysis Discord

FAQ | Documentation | Build Instructions

About

SerenityOS is a love letter to '90s user interfaces with a custom Unix-like core. It flatters with sincerity by stealing beautiful ideas from various other systems.

Roughly speaking, the goal is a marriage between the aesthetic of late-1990s productivity software and the power-user accessibility of late-2000s *nix. This is a system by us, for us, based on the things we like.

You can watch videos of the system being developed on YouTube:

Screenshot

Screenshot as of c03b788.png

Features

  • Modern x86 64-bit kernel with pre-emptive multi-threading
  • Browser with JavaScript, WebAssembly, and more (check the spec compliance for JS, CSS, and Wasm)
  • Security features (hardware protections, limited userland capabilities, W^X memory, pledge & unveil, (K)ASLR, OOM-resistance, web-content isolation, state-of-the-art TLS algorithms, ...)
  • System services (WindowServer, LoginServer, AudioServer, WebServer, RequestServer, CrashServer, ...) and modern IPC
  • Good POSIX compatibility (LibC, Shell, syscalls, signals, pseudoterminals, filesystem notifications, standard Unix utilities, ...)
  • POSIX-like virtual file systems (/proc, /dev, /sys, /tmp, ...) and ext2 file system
  • Network stack and applications with support for IPv4, TCP, UDP; DNS, HTTP, Gemini, IMAP, NTP
  • Profiling, debugging and other development tools (Kernel-supported profiling, detailed program analysis with software emulation in UserspaceEmulator, CrashReporter, interactive GUI playground, HexEditor, HackStudio IDE for C++ and more)
  • Libraries for everything from cryptography to OpenGL, audio, JavaScript, GUI, playing chess, ...
  • Support for many common and uncommon file formats (PNG, JPEG, GIF, MP3, WAV, FLAC, ZIP, TAR, PDF, QOI, Gemini, ...)
  • Unified style and design philosophy, flexible theming system, custom (bitmap and vector) fonts
  • Games (Solitaire, Minesweeper, 2048, chess, Conway's Game of Life, ...) and demos (CatDog, Starfield, Eyes, mandelbrot set, WidgetGallery, ...)
  • Every-day GUI programs and utilities (Spreadsheet with JavaScript, TextEditor, Terminal, PixelPaint, various multimedia viewers and players, Mail, Assistant, Calculator, ...)

... and all of the above are right in this repository, no extra dependencies, built from-scratch by us :^)

Additionally, there are over two hundred ports of popular open-source software, including games, compilers, Unix tools, multimedia apps and more.

How do I read the documentation?

Man pages are available online at man.serenityos.org. These pages are generated from the Markdown source files in Base/usr/share/man and updated automatically.

When running SerenityOS you can use man for the terminal interface, or help for the GUI.

Code-related documentation can be found in the documentation folder.

How do I build and run this?

See the SerenityOS build instructions. Serenity runs on Linux, macOS (aarch64 might be a challenge), Windows (with WSL2) and many other *Nixes with hardware or software virtualization.

Get in touch and participate!

Join our Discord server: SerenityOS Discord

Before opening an issue, please see the issue policy.

A general guide for contributing can be found in CONTRIBUTING.md.

Authors

And many more! See here for a full contributor list. The people listed above have landed more than 100 commits in the project. :^)

License

SerenityOS is licensed under a 2-clause BSD license.