- NAME
- Description
  - Detecting Hanging Processes
- Maintainers
- Authors

# NAME

Debugging mod_perl Perl Internals

# Description

This document explains how to debug Perl code under mod_perl.

Most of the mod_perl 1.0 debug documentation applies to mod_perl 2.0:

## Detecting Hanging Processes

See Hanging Processes: Detection and Diagnostics for the explanation, but under mp2 to use signals to detect where the process is spinning, you can't use `$SIG{USR2}`, you have to use POSIX signals. i.e. the code becomes:

     use Carp ();
     use POSIX qw(SIGUSR2);
     my $mask      = POSIX::SigSet->new( SIGUSR2 );
     my $action    = POSIX::SigAction->new(\&tell_where_spinning, $mask);
     my $oldaction = POSIX::SigAction->new();
     POSIX::sigaction(SIGUSR2, $action, $oldaction );

     sub tell_where_spinning {
         Carp::confess("caught SIGUSR2!");
     };

and then:

    % kill USR2 <pid_of_the_spinning_process>

and watch for the trace in error_log.

# Maintainers

Maintainer is the person(s) you should contact with updates, corrections and patches.

- Stas Bekman [http://stason.org/]

# Authors

- Stas Bekman [http://stason.org/]

Only the major authors are listed above. For contributors see the Changes file.