alarm, Signals, http://perldoc.perl.org/perlipc.html#Deferred_Signals_(Safe_Signals)

Please be specific to the 2 cases that I mentioned and tell me how can we tell which case's signals are safe and which case's are not, and most importantly WHY.

CASE 1:


#!/usr/bin/perl 

require 'myconfigure.cgi';
$timeout = 5;
use DBI;
$keywords = "Whether rocking natural-curls, a-short";

print "Content-type: text/html\n\n";
sub do_search {

    $time1 = time;

    $dbh=DBI->connect("dbi:mysql:$database:localhost","$username","$pa
ssword");

    $keywords_quoted = $dbh ->quote ($keywords);
    $query="SELECT count(*) FROM $websites_table WHERE MATCH(title) AG
AINST ($keywords_quoted)";
    $sth=$dbh->prepare(qq{$query});
    $sth->execute();
    $total_count = $sth->fetchrow_array ();
    $sth->finish;
    $dbh->disconnect ||die("Couldn't disconnect to database!\n");
    $time2 = time;
    $time_ran = $time2 - $time1;

}

eval {        
    local $SIG{ALRM} = sub { die "alarm\n" }; 
    alarm $timeout;        
    &do_search;        
    alarm 0;    
}; 

if($@) {        
    $time2 = time;
    $time_ran = $time2 - $time1;

    print "$@, Time Ran: $time_ran, Total Count: $total_count\n";
    exit;

}

print "Time Ran: $time_ran, Total Count: $total_count\n";
exit;
[download]


CASE 2:


#!/usr/bin/perl 

$max_time = 5;
$timeout = 3;
use DBI;

print "Content-type: text/html\n\n";
sub do_counter {

    $time1 = time;
    $time2 = time;
    $counter = 0;
    $time_ran = $time2 - $time1;

    $dbh=DBI->connect("dbi:mysql:$database:localhost","username","pass
word");

    $query="SELECT name FROM test";
    $sth=$dbh->prepare($query);
    $sth->execute();
    while ( @row = $sth->fetchrow_array ) {

        while($time_ran <= $max_time) {

            $conter++;
            $time2 = time;
            $time_ran = $time2 - $time1;
        } 
                                        
    }

    $sth->finish;

    $dbh->disconnect ||die("Couldn't disconnect to database!\n");

}


eval {        
        local $SIG{ALRM} = sub { die "alarm\n" }; 
        alarm $timeout;        
        &do_counter;        
        alarm 0;    
}; 

if($@) {        
        print "$@, Time Ran: $time_ran, Counter: $conter\n";
    exit;
      
}

print "Time Ran: $time_ran, Counter: $conter\n";
exit;
[download]


NOTES: I've a feeling you don't understand the issue in the thread, simply making empty statement.