=head1 NAME

Debugging mod_perl Perl Internals

=head1 Description

This document explains how to debug Perl code under mod_perl.

Most of the L<mod_perl 1.0 debug
documentation|docs::1.0::guide::debug> applies to mod_perl 2.0:





=head2 Detecting Hanging Processes

See L<Hanging Processes: Detection and
Diagnostics|docs::1.0::guide::debug/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 C<$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 F<error_log>.





=head1 Maintainers

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

=over

=item *

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

=back

=head1 Authors

=over

=item *

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

=back

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

=cut