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kleines Filmröllchen b645f87b7a Kernel: Overhaul system shutdown procedure 
For a long time, our shutdown procedure has basically been:
- Acquire big process lock.
- Switch framebuffer to Kernel debug console.
- Sync and lock all file systems so that disk caches are flushed and
  files are in a good state.
- Use firmware and architecture-specific functionality to perform
  hardware shutdown.

This naive and simple shutdown procedure has multiple issues:
- No processes are terminated properly, meaning they cannot perform more
  complex cleanup work. If they were in the middle of I/O, for instance,
  only the data that already reached the Kernel is written to disk, and
  data corruption due to unfinished writes can therefore still occur.
- No file systems are unmounted, meaning that any important unmount work
  will never happen. This is important for e.g. Ext2, which has
  facilites for detecting improper unmounts (see superblock's s_state
  variable) and therefore requires a proper unmount to be performed.
  This was also the starting point for this PR, since I wanted to
  introduce basic Ext2 file system checking and unmounting.
- No hardware is properly shut down beyond what the system firmware does
  on its own.
- Shutdown is performed within the write() call that asked the Kernel to
  change its power state. If the shutdown procedure takes longer (i.e.
  when it's done properly), this blocks the process causing the shutdown
  and prevents any potentially-useful interactions between Kernel and
  userland during shutdown.

In essence, current shutdown is a glorified system crash with minimal
file system cleanliness guarantees.

Therefore, this commit is the first step in improving our shutdown
procedure. The new shutdown flow is now as follows:
- From the write() call to the power state SysFS node, a new task is
  started, the Power State Switch Task. Its only purpose is to change
  the operating system's power state. This task takes over shutdown and
  reboot duties, although reboot is not modified in this commit.
- The Power State Switch Task assumes that userland has performed all
  shutdown duties it can perform on its own. In particular, it assumes
  that all kinds of clean process shutdown have been done, and remaining
  processes can be hard-killed without consequence. This is an important
  separation of concerns: While this commit does not modify userland, in
  the future SystemServer will be responsible for performing proper
  shutdown of user processes, including timeouts for stubborn processes
  etc.
- As mentioned above, the task hard-kills remaining user processes.
- The task hard-kills all Kernel processes except itself and the
  Finalizer Task. Since Kernel processes can delay their own shutdown
  indefinitely if they want to, they have plenty opportunity to perform
  proper shutdown if necessary. This may become a problem with
  non-cooperative Kernel tasks, but as seen two commits earlier, for now
  all tasks will cooperate within a few seconds.
- The task waits for the Finalizer Task to clean up all processes.
- The task hard-kills and finalizes the Finalizer Task itself, meaning
  that it now is the only remaining process in the system.
- The task syncs and locks all file systems, and then unmounts them. Due
  to an unknown refcount bug we currently cannot unmount the root file
  system; therefore the task is able to abort the clean unmount if
  necessary.
- The task performs platform-dependent hardware shutdown as before.

This commit has multiple remaining issues (or exposed existing ones)
which will need to be addressed in the future but are out of scope for
now:
- Unmounting the root filesystem is impossible due to remaining
  references to the inodes /home and /home/anon. I investigated this
  very heavily and could not find whoever is holding the last two
  references.
- Userland cannot perform proper cleanup, since the Kernel's power state
  variable is accessed directly by tools instead of a proper userland
  shutdown procedure directed by SystemServer.

The recently introduced Firmware/PowerState procedures are removed
again, since all of the architecture-independent code can live in the
power state switch task. The architecture-specific code is kept,
however.
2023-07-15 00:12:01 +02:00
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Base Base: Add more emoji 2023-07-14 15:42:48 -04:00
Documentation Documentation: Add qt6-multimedia-devel on openSUSE for Ladybird 2023-07-09 08:06:13 +01:00
Kernel Kernel: Overhaul system shutdown procedure 2023-07-15 00:12:01 +02:00
Ladybird Ladybird: Allow loading 'data:' URLs from a search bar 2023-07-11 15:30:11 +02:00
Meta README+Meta: Update the screenshot :^) 2023-07-14 23:40:58 +02:00
Ports Ports: Remove the separate branch for extracting .tar.gz files 2023-07-13 05:09:46 +02:00
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.prettierignore LibJS: Add DisposableStack{, Prototype, Constructor} 2023-01-23 09:56:50 +00:00
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.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
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README.md README+Meta: Update the screenshot :^) 2023-07-14 23:40:58 +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.

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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.