in reply to Alarm and blocking I/O.

Read http://search.cpan.org/~jesse/perl-5.12.1/pod/perlipc.pod#Deferred_Signals_(Safe_Signals). It explains the problem and offers various solutions.

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Re^2: Alarm and blocking I/O.
by expresspotato (Beadle) on May 29, 2010 at 17:55 UTC
    Hmm I am using perl 5.10.0, so perlio is used by default. I also tried setting the signal handler with use POSIX qw(SIGALRM);. No luck there either. The alarm eventually gets called but about a minute later, most likely when the NFS operation times out because of its mount options. Any help would be greatly appreciated :)
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        Thanks for your prompt reply BrowserUK. That still doesn't do the trick. The following code is used to include the Perl::Unsafe::Signals module. 
              use Perl::Unsafe::Signals;
      print "Evaluating... \n";
      #eval{
         local $SIG{ALRM} = sub {
            $sys_check_mount{$mount_server} = 0;
            print "Alarm!";
            exit();
         };
         alarm(5);
         print "Alarm Set... Trying system commands... \n";
         UNSAFE_SIGNALS {
            print "Using unsafe signals... \n";
            if (-e $mount_server_check_path && utime(undef, undef, "$m
+ount_server_check_path/mount_check")){
               #print "OK\n";
               $sys_check_mount{$mount_server} = 1;
            }else{
               #print "Broken\n";
               $sys_check_mount{$mount_server} = 0;
               push (@mount_server_broken,$mount_server);
            }
         };
         alarm(0);
         print "Reset Alarm... \n";

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        Any other suggestions are appreciated :) Upon further investigation it seems something must be a-miss somewhere else in the program. The following code sniplet alarm's just fine: 
        perl -e 'alarm shift @ARGV; exec @ARGV' 3 touch /node/store1/videos/mo
+unt_check

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Re^2: Alarm and blocking I/O.
by expresspotato (Beadle) on May 29, 2010 at 22:04 UTC
    It seems replacing the default signal is the cause of the alarm failing to go off. I do not understand why, even this simple replacement causes the alarm to not go off. 
       $SIG{ALRM} = sub { die "alarm" };

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    Without it, the alarm does fire. Anyone can clarify why this is?
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      Sorry, my needs of alarm are relatively simple, which is just as well because as with anything signalish, simple is all you get on Win32.

      I've previously used the environment variable PERL_SIGNALS=unsafe, but recently discovered Perl::Unsafe::Signals which works for me and limits the scope. All I could do was pass on the information, as you're doing things I don't understand on a platform I don't use.

      Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
      "Science is about questioning the status quo. Questioning authority".
      In the absence of evidence, opinion is indistinguishable from prejudice.
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      Huh... To anyone curious on how it is now working: Not checking for the file's existence before touching it and not touching it with utime. 
      if (system(qq~ touch "$mount_server_check_path/mount_check"; ~)){ ...

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      Perl :p
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