[jboss-dev] Thread safety problems

When writing an API or SPI it is absolutely critical that all the elements of that API or SPI are thoroughly documented with any information related to the thread safety (or lack thereof) of that element. We have a great deal of code (and I'm talking critical, core stuff) out there with little or no javadoc at all, let alone thread safety information in said documentation. This creates the possibility for situations like SPIs which can end up being implemented with completely wrong thread safety semantics, basically leaving time bombs in the code. See http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4226025 for one recent example. We still have way too much code doing double-checked locking, or using locks in strange or non-optimal ways, or using thread interruption wrong, or making wrong assumptions about the JMM. Own and read this book: http://jcip.net/ - don't think you understand concurrency until you have done so - seriously. Thread interruption in particular is easy to do right. When handling InterruptedException, you basically have two choices. Either rethrow it *directly* (absolutely no re-wrapping allowed!), or re-set the thread interrupt status (either way, there's no need to log the exception - that will just lead to noise). If you do the latter, you have a choice as to whether you want to cancel or short-circuit the current operation (which should be done in as sane and predictable a way as possible - don't just blow up with a RuntimeException!), or complete what you're doing. Interruption happens guys, that's how thread pools are usually shut down and tasks (which your code may be a part of) are cancelled. - DML