/usr/share/perl5/Log/Log4perl/Util/Semaphore.pm is in liblog-log4perl-perl 1.29-1ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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package Log::Log4perl::Util::Semaphore;
#//////////////////////////////////////////
use IPC::SysV qw(IPC_RMID IPC_CREAT IPC_EXCL SEM_UNDO IPC_NOWAIT
IPC_SET IPC_STAT SETVAL);
use IPC::Semaphore;
use POSIX qw(EEXIST);
use strict;
use warnings;
use constant INTERNAL_DEBUG => 0;
###########################################
sub new {
###########################################
my($class, %options) = @_;
my $self = {
key => undef,
mode => undef,
uid => undef,
gid => undef,
destroy => undef,
semop_wait => .1,
semop_retries => 1,
creator => $$,
%options,
};
$self->{ikey} = unpack("i", pack("A4", $self->{key}));
# Accept usernames in the uid field as well
if(defined $self->{uid} and
$self->{uid} =~ /\D/) {
$self->{uid} = (getpwnam $self->{uid})[2];
}
bless $self, $class;
$self->init();
my @values = ();
for my $param (qw(mode uid gid)) {
push @values, $param, $self->{$param} if defined $self->{$param};
}
$self->semset(@values) if @values;
return $self;
}
###########################################
sub init {
###########################################
my($self) = @_;
print "Semaphore init '$self->{key}'/'$self->{ikey}'\n" if INTERNAL_DEBUG;
$self->{id} = semget( $self->{ikey},
1,
&IPC_EXCL|&IPC_CREAT|($self->{mode}||0777),
);
if(! defined $self->{id} and
$! == EEXIST) {
print "Semaphore '$self->{key}' already exists\n" if INTERNAL_DEBUG;
$self->{id} = semget( $self->{ikey}, 1, 0 )
or die "semget($self->{ikey}) failed: $!";
} elsif($!) {
die "Cannot create semaphore $self->{key}/$self->{ikey} ($!)";
}
}
###########################################
sub status_as_string {
###########################################
my($self, @values) = @_;
my $sem = IPC::Semaphore->new($self->{ikey}, 1, 0);
my $values = join('/', $sem->getall());
my $ncnt = $sem->getncnt(0);
my $pidlast = $sem->getpid(0);
my $zcnt = $sem->getzcnt(0);
my $id = $sem->id();
return <<EOT;
Semaphore Status
Key ...................................... $self->{key}
iKey ..................................... $self->{ikey}
Id ....................................... $id
Values ................................... $values
Processes waiting for counter increase ... $ncnt
Processes waiting for counter to hit 0 ... $zcnt
Last process to perform an operation ..... $pidlast
EOT
}
###########################################
sub semsetval {
###########################################
my($self, %keyvalues) = @_;
my $sem = IPC::Semaphore->new($self->{ikey}, 1, 0);
$sem->setval(%keyvalues);
}
###########################################
sub semset {
###########################################
my($self, @values) = @_;
print "Setting values for semaphore $self->{key}/$self->{ikey}\n" if
INTERNAL_DEBUG;
my $sem = IPC::Semaphore->new($self->{ikey}, 1, 0);
$sem->set(@values);
}
###########################################
sub semlock {
###########################################
my($self) = @_;
my $operation = pack("s!*",
# wait until it's 0
0, 0, 0,
# increment by 1
0, 1, SEM_UNDO
);
print "Locking semaphore '$self->{key}'\n" if INTERNAL_DEBUG;
$self->semop($self->{id}, $operation);
}
###########################################
sub semunlock {
###########################################
my($self) = @_;
# my $operation = pack("s!*",
# # decrement by 1
# 0, -1, SEM_UNDO
# );
#
print "Unlocking semaphore '$self->{key}'\n" if INTERNAL_DEBUG;
# # ignore errors, as they might result from trying to unlock an
# # already unlocked semaphor.
# semop($self->{id}, $operation);
semctl $self->{id}, 0, SETVAL, 0;
}
###########################################
sub remove {
###########################################
my($self) = @_;
print "Removing semaphore '$self->{key}'\n" if INTERNAL_DEBUG;
semctl ($self->{id}, 0, &IPC_RMID, 0) or
die "Removing semaphore $self->{key} failed: $!";
}
###########################################
sub DESTROY {
###########################################
my($self) = @_;
if($self->{destroy} && $$==$self->{creator}) {
$self->remove();
}
}
###########################################
sub semop {
###########################################
my($self, @args) = @_;
my $retries = $self->{semop_retries};
my $rc;
{
$rc = semop($args[0], $args[1]);
if(!$rc and
$! =~ /temporarily unavailable/ and
$retries-- > 0) {
$rc = 'undef' unless defined $rc;
print "semop failed (rc=$rc), retrying\n",
$self->status_as_string if INTERNAL_DEBUG;
select undef, undef, undef, $self->{semop_wait};
redo;
}
}
$rc or die "semop(@args) failed: $! ";
$rc;
}
1;
__END__
=head1 NAME
Log::Log4perl::Util::Semaphore - Easy to use semaphores
=head1 SYNOPSIS
use Log::Log4perl::Util::Semaphore;
my $sem = Log::Log4perl::Util::Semaphore->new( key => "abc" );
$sem->semlock();
# ... critical section
$sem->semunlock();
$sem->semset( uid => (getpwnam("hugo"))[2],
gid => 102,
mode => 0644
);
=head1 DESCRIPTION
Log::Log4perl::Util::Semaphore provides the synchronisation mechanism
for the Synchronized.pm appender in Log4perl, but can be used independently
of Log4perl.
As a convenience, the C<uid> field accepts user names as well, which it
translates into the corresponding uid by running C<getpwnam>.
=head1 COPYRIGHT AND LICENSE
Copyright 2002-2009 by Mike Schilli E<lt>m@perlmeister.comE<gt>
and Kevin Goess E<lt>cpan@goess.orgE<gt>.
This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.
=cut
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