Jan Oravec
58c030adc8
A race condition can occur when the processing thread tries to notify condition that is not yet waited upon. This can happen during the short window in the web request thread between transitioning to the WAITING state and calling condition.wait(). Fix this by locking mutex right before notifying the condition. If the web request thread is in WAITING state, it is guaranteed to hold the mutex or wait for condition variable. If the processing thread was able to transition away from the WAITING state and grabbed the lock, the web request thread must be waiting on condition variable, so it is safe to notify it. Thanks @andrii for tracking the bug down to ExternalThreadEvents and providing a workaround (grabbing the mutex few lines up than this diff).
HipHop VM for PHP 
HipHop VM (HHVM) is a new open-source virtual machine designed for executing programs written in PHP. HHVM uses a just-in-time compilation approach to achieve superior performance while maintaining the flexibility that PHP developers are accustomed to. HipHop VM (and before it HPHPc) has realized > 5x increase in throughput for Facebook compared with Zend PHP 5.2.
HipHop is most commonly run as a standalone server, replacing both Apache and modphp.
Installing
You can install a prebuilt package or compile from source.
Running
You can run standalone programs just by passing them to hhvm: hhvm my_script.php.
HipHop bundles in a webserver. So if you want to run on port 80 in the current directory:
sudo hhvm -m server
For anything more complicated, you'll want to make a config.hdf and run sudo hhvm -m server -c config.hdf.
Contributing
We'd love to have your help in making HipHop better. If you run into problems, please open an issue, or better yet, fork us and send a pull request. Join us on #hhvm on freenode.
If you want to help but don't know where to start, try fixing some of the Zend tests that don't pass. You can run them with hphp/test/run. When they work, move them to zend/good and send a pull request.
Before changes can be accepted a Contributors Licensing Agreement (pdf - print, sign, scan, link) must be signed.
Licence
HipHop VM is licensed under the PHP and Zend licenses except as otherwise noted.