5dc16e2f43
Summary: # A race condition The practical thing of this diff is fixing a data race. Imagine a case where a thread A calls `addObserver` and thread B calls `nativeImageResponseFailed` at the same time. Thread A might read `status_` exclusively and store result as a local variable and then go sleep. Then thread B starts and finishes `nativeImageResponseFailed`, it writes `status_` and notifies all observers. Then thread B wakes up. It adds an observer to a collection of observers and finishes. As a result, the observer from `addObserver` will never be called. To fix this, we changed a logic a bit to lock only once per method. During the lock, we read and/or write to storage and then perform side-effects. In contrast, previously we often locked only around the access of a particular instance variable (several times per method). The challenge here is that idiomatic/fancy to C++/STL ways to lock mutexes don't work in our case. # C++ idioms and readability, multiple locks for the same transaction STL has tools to avoid calling `lock` and `unlock` methods manually (std::lock_guard<> and lamdas). Unfortunately, using that in our use case is quite problematic. That's probably possible but will lead to much less readable code and some copy-pasta in `addObserver`. Therefore we replaced using `std::lock_guard` with simple `lock` and `unlock` where using `std::lock_guard` was problematic. # Why we changed `shared_mutex` to a normal one? After consolidating the locks we found that we have an only case where we can use shared lock (in `nativeImageResponseProgress`). Calling this method in real life is not concurrent, so it makes sense to replace a shared lock with a more simple and performant regular one. Reviewed By: sammy-SC Differential Revision: D17368739 fbshipit-source-id: 61d66fb737d8c2dc73001a80a31edaa59a16d886 |
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README.md
React Native
Learn once, write anywhere:
Build mobile apps with React.
Getting Started · Learn the Basics · Showcase · Contribute · Community · Support
React Native brings React's declarative UI framework to iOS and Android. With React Native, you use native UI controls and have full access to the native platform.
- Declarative. React makes it painless to create interactive UIs. Declarative views make your code more predictable and easier to debug.
- Component-Based. Build encapsulated components that manage their own state, then compose them to make complex UIs.
- Developer Velocity. See local changes in seconds. Changes to JavaScript code can be live reloaded without rebuilding the native app.
- Portability. Reuse code across iOS, Android, and other platforms.
React Native is developed and supported by many companies and individual core contributors. Find out more in our ecosystem overview.
Contents
- Requirements
- Building your first React Native app
- Documentation
- Upgrading
- How to Contribute
- Code of Conduct
- License
📋 Requirements
React Native apps may target iOS 9.0 and Android 4.1 (API 16) or newer. You may use Windows, macOS, or Linux as your development operating system, though building and running iOS apps is limited to macOS. Tools like Expo can be used to work around this.
🎉 Building your first React Native app
Follow the Getting Started guide. The recommended way to install React Native depends on your project. Here you can find short guides for the most common scenarios:
📖 Documentation
The full documentation for React Native can be found on our website.
The React Native documentation discusses components, APIs, and topics that are specific to React Native. For further documentation on the React API that is shared between React Native and React DOM, refer to the React documentation.
The source for the React Native documentation and website is hosted on a separate repo, @facebook/react-native-website.
🚀 Upgrading
Upgrading to new versions of React Native may give you access to more APIs, views, developer tools and other goodies. See the Upgrading Guide for instructions.
React Native releases are discussed in the React Native Community, @react-native-community/react-native-releases.
👏 How to Contribute
The main purpose of this repository is to continue evolving React Native core. We want to make contributing to this project as easy and transparent as possible, and we are grateful to the community for contributing bugfixes and improvements. Read below to learn how you can take part in improving React Native.
Code of Conduct
Facebook has adopted a Code of Conduct that we expect project participants to adhere to. Please read the full text so that you can understand what actions will and will not be tolerated.
Contributing Guide
Read our Contributing Guide to learn about our development process, how to propose bugfixes and improvements, and how to build and test your changes to React Native.
Open Source Roadmap
You can learn more about our vision for React Native in the Roadmap.
Good First Issues
We have a list of good first issues that contain bugs which have a relatively limited scope. This is a great place to get started, gain experience, and get familiar with our contribution process.
Discussions
Larger discussions and proposals are discussed in @react-native-community/discussions-and-proposals.
📄 License
React Native is MIT licensed, as found in the LICENSE file.
React Native documentation is Creative Commons licensed, as found in the LICENSE-docs file.