[jboss-dev] Thread safety problems

[Scott Marlow]

Anil Saldhana wrote:
> Jason T. Greene wrote:
>> 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.
> Should we also maybe start a "Best Practices" wiki article or such for 
> folks to review often? It is just not thread safety that we need to be 
> worried. Things such as privileged blocks also need to be taught.  
> JCIP is one of the best books I have ever read. :)
>

http://www.jboss.org/community/docs/DOC-12399 has some thread safety 
thoughts.  Perhaps others could be added.

> We have got to continue and enhance the culture of design discussions 
> and the use of this development list. :)
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