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Re^5: Setting signal handlers

by ruoso (Curate)
on May 09, 2006 at 23:18 UTC ( #548349=note: print w/replies, xml ) Need Help??


in reply to Re^4: Setting signal handlers
in thread Setting signal handlers

Hmmm... a crash-test told me it's still not so trustworthy... Still got lost signals and duplicated responses...

Summary
PID: LOST SIGNALS
5023: 3
5024: 12
5025: 12
5026: 3
5027: 6
5028: 5
5029: 6
5030: 1
5031: 4
5032: 8
parent: 9319
PID: MAX_TIME, MIN_TIME, COUNT, MED
5023: 0.0395898818969727, 2.00271606445312e-05, 997, 0.000217293066868452
5024: 0.0297799110412598, 2.98023223876953e-05, 988, 0.00015578627103736
5025: 0.0275199413299561, -0.00189995765686035, 988, 0.0001988222724513
5026: 0.0194199085235596, 2.98023223876953e-05, 997, 0.000203705599219534
5027: 0.0242300033569336, 2.00271606445312e-05, 994, 0.000233370053696201
5028: 0.0375699996948242, 2.98023223876953e-05, 995, 0.000291356609095281
5029: 0.0186100006103516, 2.98023223876953e-05, 994, 0.000193814636476083
5030: 0.0270700454711914, 2.98023223876953e-05, 999, 0.000180974498286739
5031: 0.0173900127410889, 1.97887420654297e-05, 996, 0.000126030071672187
5032: 0.0372300148010254, 2.98023223876953e-05, 992, 0.000203564522727843
parent: 0.0304899215698242, -0.016819953918457, 10551, 0.000104144584193703

The negative MIN_TIME means that a response was sent before the signal (in a stack)...

Follows the code to do the crash-test...

#!/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;

And the code to generate the summary:

#!/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/$count.$/; }
daniel

Replies are listed 'Best First'.
Re^6: Setting signal handlers
by dave_the_m (Monsignor) on May 10, 2006 at 00:17 UTC
    Perl will only call a particular signal handler once per signal number - no matter how many times it recieves that signal type *before* handling it.

    But there's a general flaw with your stress code; you have multiple processes all writing to stdout (which I presume is redirected to a file), and that's likely to lose or duplicate output, even with $|=1:

    $ cat /tmp/p1 #!/usr/bin/perl $| = 1; for (1..10) { if (fork == 0) { print "$_\n" for 1..100; exit; } } $ perl588 /tmp/p1 > /tmp/x ; wc -l /tmp/x 900 /tmp/x $ perl588 /tmp/p1 > /tmp/x ; wc -l /tmp/x 983 /tmp/x $ perl588 /tmp/p1 > /tmp/x ; wc -l /tmp/x 1000 /tmp/x
    Either open the file in append mode and only syswrite to it, or have each process write to a separate file.

    Dave.

      well the output surprises me...at the OS level a child will get a copy of the parent descriptor but __does share__ the file offset, so if they write at the same time, their output will be intermixed. but i really don't see how you can lose any \n on cygwin I cannot reproduce what you get tomorrow at work I will try on HP-UX... 100 runs with 1000 print in each process

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