stas 2002/08/30 05:23:07 Modified: src/docs/2.0/user/coding coding.pod Log: document the Threads Coding Issues Revision Changes Path 1.15 +42 -6 modperl-docs/src/docs/2.0/user/coding/coding.pod Index: coding.pod =================================================================== RCS file: /home/cvs/modperl-docs/src/docs/2.0/user/coding/coding.pod,v retrieving revision 1.14 retrieving revision 1.15 diff -u -r1.14 -r1.15 --- coding.pod 12 Jul 2002 09:55:16 -0000 1.14 +++ coding.pod 30 Aug 2002 12:23:07 -0000 1.15 @@ -157,13 +157,49 @@ =head1 Threads Coding Issues under mod_perl -Of course first of all study how the new ithreads Perl model works, by -reading the I<perlthrtut>, I<threads> and I<threads::shared> manpages. +The following sections discuss threading issues when running mod_perl +under a threaded MPM. -Artur Bergman explains how to port pure Perl modules to work properly -with Perl ithreads. Issues with chdir() and other functions that rely -on shared process' datastructures are discussed. -http://www.perl.com/lpt/a/2002/06/11/threads.html +=head2 Thread-environment Issues + +The only thing you have to worry about your code is that it's +thread-safe and that you don't use functions that affect all threads. + +Perl 5.8.0 itself is a thread-safe. That means that operations like +C<push()>, C<map()>, C<chomp()>, C<=>, C</>, C<+=>, etc. are +thread-safe. Operations that involve system calls, may or may not be +thread-safe. It all depends on whether the underlying C libraries used +by the perl functions are thread-safe. + +For example the function C<localtime()> is not thread-safe when the +implementation of asctime(3) is not thread-safe. Other usually +problematic functions include readdir(), srand(), etc. + +Another important issue that shouldn't be missed is what some people +refer to as I<thread-locality>. Certain functions executed in a single +thread affect the whole process and therefore all other threads +running inside that process. For example if you C<chdir()> in one +thread, all other thread now see the current working directory of that +thread that C<chdir()>'ed to that directory. Other functions with +similar effects include C<umask()>, C<chroot()>, etc. Currently there +is no cure for this problem. You have to find these functions in your +code and replace them with different workarounds. + +=head2 Deploying Threads + +This is actually quite unrelated to mod_perl 2.0. You don't have to +know much about Perl threads, other than L<Thread-environment +Issues|/Thread_environment_Issues>, to have your code properly work +under threaded MPM mod_perl. + +If you want to spawn your own threads, first of all study how the new +ithreads Perl model works, by reading the I<perlthrtut>, I<threads> +and I<threads::shared> manpages. + +Artur Bergman wrote an article which explains how to port pure Perl +modules to work properly with Perl ithreads. Issues with chdir() and +other functions that rely on shared process' datastructures are +discussed. http://www.perl.com/lpt/a/2002/06/11/threads.html =head1 Maintainers
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