Thomas Busch wrote:
Hi,I'm the author of a perl XS module which is a wrapper around a C++ library that is thread-safe. However in the context of Perl is doesn't seem to be. When I do the following: =============================== #!/usr/bin/perl use Lucene; use threads; use strict; my $analyzer = new Lucene::Analysis::Standard::StandardAnalyzer; sub test { print "pass\n"; }; my $thr = threads->create('test'); $thr->join(); undef $analyzer; print "pass2\n"; exit(0); =============================== I get: pass Segmentation fault It seems there is a problem during the destruction of the object that was created before threads->create. What could be the cause of this problem ? The source code of the XS module is here: http://search.cpan.org/src/TBUSCH/Lucene-0.13/ What are the usual things to look out for when writing thread-safe XS modules that use external libraries ? Thomas.
I didn't see any CLONE() method in your code (tho admittedly, I didn't do a deep inspection, theres a lot of XS files there). Perhaps you need a CLONE() method to cleanup some context in the child thread's cloned copy of the StandardAnalyzer object ? (Or maybe in the parent's version of the object ?) In similar situations, I've had to tag resources with the thread id in which they were created, and make sure they get destroyed in that same thread, to avoid destruction in each cloned instance. (Or use some other explicit tag to indicate the resource has already been destroyed...but that could require mutexes if multiple threads are concurrently destroying) Alternately, you might try using a threads::shared version of the object, tho that will complicate your constructor. You may eventually need to do a deeper debug of your segfault to get exact lines where the fault occurs. Dean Arnold Presicient Corp.
