[closer-devel] Thread-safety in ContextL, and related news

[Pascal Costanza]

Hi,

I have now added the necessary synchronization to (hopefully) ensure  
that layer context caches are thread-safe in ContextL. I also checked  
the rest of the ContextL, and found one other place where  
synchronization is necessary, and added the necessary code as well.  
(The changes are only in the repository, not in the official version  
of ContextL yet.)

The synchronization is done in a way that the caches won't hold  
duplicate entries, and creating a cache entry should always lead to a  
proper update of the cache - so cache entries cannot be missed by  
other threads. It should even be the case that CL implementations with  
'real' parallelism on multicore architectures should also be safe  
(whether this matters at the moment or not is a different question ;).

ContextL now depends on portable-threads of the GBBopen project.  
Please go to http://gbbopen.org/ and download the whole package from  
there - I have tested against the version in their SVN repository. You  
need to add gbbopen.asd to your asdf central registry, GBBopen figures  
out the rest for you. (There is also an asdf-install version of  
portable-threads, but that one seems to be outdated. GBBopen doesn't  
seem to be asdf-installable itself, but I am not sure - I actually  
don't use asdf-install myself.)

I have run my test suites successfully on Allegro 7.0, 8.0 and 8.1;  
clisp 2.42 (aka 2.41.1), CMUCL 19d, LispWorks 5.02, OpenMCL 1.0 and  
SBCL 1.0.11. I couldn't test MCL, because GBBopen doesn't compile for  
MCL - I will report this to the GBBopen guys. LispWorks 4.4.x doesn't  
run on Leopard anymore, so I cannot test it. (I will probably remove  
support for LispWorks < 5.0.x in the next release of ContextL.)

Please let me know if there are any problems or questions.


Best,
Pascal

-- 
Pascal Costanza, mailto:pc at p-cos.net, http://p-cos.net
Vrije Universiteit Brussel, Programming Technology Lab
Pleinlaan 2, B-1050 Brussel, Belgium