[jboss-dev] Thread safety problems

[Jason T. Greene]

David M. Lloyd wrote:
> 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.

Well said. Every contributor should read this book, it is essential 
knowledge.

I will also add that all new designs/enhancements must take thread 
interaction into consideration. It is much harder to retrofit an 
existing API/implementation to be safe and efficient after it has been 
completed.

If you aren't sure how to solve a threading problem, or want to validate 
your design please ask here or on the forums! We have many experts in 
this area.

-- 
Jason T. Greene
JBoss, a division of Red Hat