505fdd612b
The previous implementation was prone to deadlocks when the next round of threads tried to enter the barrier before the prior round exited it. This new version takes care of that problem, and also removes some other contention. Basic design: * waiter_count is now atomic, which means only the "serial" thread, or in case of contention threads that raced, need acquire the mutex. * mutex remains locked during threads wakeup, at which point waiter_count is negative. It is only unlocked when count reaches 0 in the last-woken thread. This protects against the races that lead to deadlocks. * Remove usage of _kern_mutex_switch_lock. This was done incorrectly; if it returned EINTR, the first lock would be unlocked but the second would not be acquired, creating further races. Instead, we leave the barrier lock in "LOCKED" state at all times except when we actually want to wake threads up, when it is left "Unlocked" (and "unlocked" by each successive exiting thread, just in case.) Fixes #15736.
Haiku
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Haiku is an open-source operating system that specifically targets personal computing. Inspired by the BeOS, Haiku is fast, simple to use, easy to learn and yet very powerful.
Goals
- Sensible defaults with minimal configuration required.
- Clean, clear, concise code.
- Unified desktop environment.
Trying Haiku
Haiku provides pre-built nightly images and release images. Haiku is compatible with a large variety of hardware, but in case you don't want to "take the plunge" and install Haiku on bare metal, you can install it on a virtual machine (VM) instead. If you've never used a VM before, you can follow one of the "Emulating Haiku" guides.
Compiling Haiku
See ReadMe.Compiling.
Contributing
Haiku is a meritocratic open source project with a large variety of tasks. Even if you can't write code, you can still help! Haiku needs designers, (technical) writers, translators, testers... Get involved and help out!
Contributing code
If you're submitting a patch to us, please make sure you're following the patch submitting guidelines.
If you're having trouble finding something in the source tree, you can use one of our web-based source code browsers:
- https://xref.landonf.org/ (OpenGrok, provided by Landon Fuller)
- https://git.haiku-os.org/ (git, provided by Haiku, Inc.)
Contributing documentation
The main piece of documentation that still needs work are the API docs (found
in the tree at docs/user). Just find an undocumented class, write
documentation for it, and submit a patch.
Contributing translations
See wiki:i18n.
Contributing software ports
See HaikuPorts.
Contributing to our infrastructure
See Infrastructure.