perf/trace/scripting: rwtop script cleanup

A couple of fixes for the rwtop script:

- printing the totals and clearing the hashes in the signal handler
eventually leads to various random and serious problems when running
the rwtop script continuously. Moving the print_totals() calls to
the event handlers solves that problem, and the event handlers are
invoked frequently enough that it doesn't affect the timeliness of
the output.

- Fix nuisance 'use of uninitialized value' warnings

Cc: Frédéric Weisbecker <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Message-Id: <[e-mail]>
Signed-off-by: Tom Zanussi <[e-mail]>
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/scripts/perl/rwtop.pl

···
 my $default_interval = 3;
 my $nlines = 20;
 my $print_thread;
+my $print_pending = 0;
 
 my %reads;
 my %writes;
···
     my ($event_name, $context, $common_cpu, $common_secs, $common_nsecs,
 	$common_pid, $common_comm,
 	$nr, $ret) = @_;
+
+    print_check();
 
     if ($ret > 0) {
 	$reads{$common_pid}{bytes_read} += $ret;
···
 	$common_pid, $common_comm,
 	$nr, $fd, $buf, $count) = @_;
 
+    print_check();
+
     $reads{$common_pid}{bytes_requested} += $count;
     $reads{$common_pid}{total_reads}++;
     $reads{$common_pid}{comm} = $common_comm;
···
     my ($event_name, $context, $common_cpu, $common_secs, $common_nsecs,
 	$common_pid, $common_comm,
 	$nr, $ret) = @_;
+
+    print_check();
 
     if ($ret <= 0) {
 	$writes{$common_pid}{errors}{$ret}++;
···
 	$common_pid, $common_comm,
 	$nr, $fd, $buf, $count) = @_;
 
+    print_check();
+
     $writes{$common_pid}{bytes_written} += $count;
     $writes{$common_pid}{total_writes}++;
     $writes{$common_pid}{comm} = $common_comm;
···
 
 sub trace_begin
 {
-    $SIG{ALRM} = \&print_totals;
+    $SIG{ALRM} = \&set_print_pending;
     alarm 1;
 }
 
···
 {
     print_unhandled();
     print_totals();
+}
+
+sub print_check()
+{
+    if ($print_pending == 1) {
+	$print_pending = 0;
+	print_totals();
+    }
+}
+
+sub set_print_pending()
+{
+    $print_pending = 1;
+    alarm $interval;
 }
 
 sub print_totals
···
     printf("%6s  %-20s  %10s  %10s  %10s\n", "------", "--------------------",
 	   "----------", "----------", "----------");
 
-    foreach my $pid (sort {$reads{$b}{bytes_read} <=>
-			       $reads{$a}{bytes_read}} keys %reads) {
-	my $comm = $reads{$pid}{comm};
-	my $total_reads = $reads{$pid}{total_reads};
-	my $bytes_requested = $reads{$pid}{bytes_requested};
-	my $bytes_read = $reads{$pid}{bytes_read};
+    foreach my $pid (sort { ($reads{$b}{bytes_read} || 0) <=>
+			       ($reads{$a}{bytes_read} || 0) } keys %reads) {
+	my $comm = $reads{$pid}{comm} || "";
+	my $total_reads = $reads{$pid}{total_reads} || 0;
+	my $bytes_requested = $reads{$pid}{bytes_requested} || 0;
+	my $bytes_read = $reads{$pid}{bytes_read} || 0;
 
 	printf("%6s  %-20s  %10s  %10s  %10s\n", $pid, $comm,
 	       $total_reads, $bytes_requested, $bytes_read);
···
     printf("%6s  %-20s  %10s  %13s\n", "------", "--------------------",
 	   "----------", "-------------");
 
-    foreach my $pid (sort {$writes{$b}{bytes_written} <=>
-			       $writes{$a}{bytes_written}} keys %writes) {
-	my $comm = $writes{$pid}{comm};
-	my $total_writes = $writes{$pid}{total_writes};
-	my $bytes_written = $writes{$pid}{bytes_written};
+    foreach my $pid (sort { ($writes{$b}{bytes_written} || 0) <=>
+			($writes{$a}{bytes_written} || 0)} keys %writes) {
+	my $comm = $writes{$pid}{comm} || "";
+	my $total_writes = $writes{$pid}{total_writes} || 0;
+	my $bytes_written = $writes{$pid}{bytes_written} || 0;
 
 	printf("%6s  %-20s  %10s  %13s\n", $pid, $comm,
 	       $total_writes, $bytes_written);
···
 
     %reads = ();
     %writes = ();
-    alarm $interval;
 }
 
 my %unhandled;