use warnings ; use strict ;

my $MASK    = @ARGV ? shift(@ARGV) : 1 ;
my $TWIDDLE = @ARGV ? shift(@ARGV) : 1 ;

$| = 1 ;

use POSIX qw(:signal_h) ;
use Time::HiRes qw(time) ;

my $main_alrm = 0 ;
my $temp_alrm = 0 ;

$SIG{ALRM} = sub { $main_alrm++ ; };

sub set_temp_alrm {
  my $sigset   = POSIX::SigSet->new ;
  my $blockset = POSIX::SigSet->new( SIGALRM ) ;

  sigprocmask(SIG_BLOCK, $blockset, $sigset)   if $MASK ;
  local $SIG{ALRM} = sub { $temp_alrm++ ; } ;
  sigprocmask(SIG_SETMASK, $sigset)            if $MASK ;

  my $t = $TWIDDLE ; while ($t) { $t-- ; } ;
} ;

if (fork) {
  print "parent started  MASK=$MASK TWIDDLE=$TWIDDLE\n" ;
  my $start = time ;
  my $next  = $start ;
  while (1) {
    set_temp_alrm() ;
    my $now = time ;
    if ($now > $next) {
      printf "main:%6d  temp:%6d  after:%6.1fs\n",
                               $main_alrm, $temp_alrm, $now-$start ;
      $next = $now + 1 ; 
    } ;
  } ;
}
else {
  print "child started\n" ;
  sleep 2 ;
  print "ALRM storm started\n";
  1 while kill ALRM => getppid;
} ;