#!/usr/bin/perl
use strict;
use warnings;
use Time::HiRes 'usleep';
my $num_processes = 10;
my $signals_per_process = 1000;
$| = 1;
my @pids;
$SIG{USR2} = sub { print "parent received ".Time::HiRes::time().$/ };

FORKS:
while ($num_processes > 0) {
	my $parent = $$;
	if (my $pid = fork()) {
		push @pids, $pid;
	} else {
		$SIG{USR1} = sub { print $$." received ".Time::HiRes::time().$/; };
		while (1) {
			usleep(rand(20));
			print "parent signalled ".Time::HiRes::time().$/;
			kill('USR2',$parent) or exit;
		}
		exit;
	}
	$num_processes--;
}

for (1..$signals_per_process) {
      PROCESS:
	foreach my $id (@pids) {
		print $id." signalled ".Time::HiRes::time().$/;
		kill("USR1", $id);
		usleep(rand(20));
	}
}
exit;

##</code><code>##

#!/usr/bin/perl
use warnings;
use strict;
my %data;
my %report;
while (<STDIN>) {
	chomp;
	my ($pid, $op, $time) = split /\s/;
	if ($op eq 'signalled') {
		push @{$data{$pid}}, $time;
	} else {
		my $sigtime = pop @{$data{$pid}};
		push @{$report{$pid}}, $time - $sigtime;
	}
}

print "Summary".$/;
print "Lost:".$/;
foreach my $pid (sort keys %data) {
	print $pid.": ".scalar(@{$data{$pid}}).$/;
}
print "Received: ".$/;
foreach my $pid (sort keys %report) {
	my ($min, $max, $count, $sum);
	foreach my $time (@{$report{$pid}}) {
		$min = $time if (not defined $min or $min > $time);
		$max = $time if (not defined $max or $max < $time);
		$count++;
		$sum += $time;
	}
	print $pid.": $max, $min, $count, ".$sum/$count.$/;
}