Re: [PATCH] Attempt at improving the perlipc docs

On Thu, Apr 22, 2010 at 2:44 PM, Maik Hentsche <maik@mm-double.de> wrote:

> and I don't see any new  issues.


1. You removed the race condition by removing the functionality that caused
it. There's now no way of getting the status returned by system. Yeah, you
get the status of your children back, but you have no idea if it's from the
system child, so you can't act on it appropriately.

2. Another added issue is that it delays handling of the death of non-system
children to the next time system is called.

Fixes (2) but not (1):

use subs qw( system );

$SIG{CHLD} = sub {
    my $pid = wait();
    cleanup_child($pid) if $pid != 1;
};

sub system {
    # open3 closes <& handles
    open(local *TO_CHLD, '<&STDIN');
    my $pid = open3('<&TO_CHLD', '>&STDOUT', '>&STDERR', @_);
    cleanup_child($pid) if waitpid($pid, 0) != -1;
}

while(1){
    my $pid = fork();
    if ($pid == 0){
        ...
        exit 0;
    } else {
        ...
        system($command);
        ...
   }
}

Fixes (1) and (2):

use subs qw( system );

my %exit_codes;

$SIG{CHLD} = sub {
    local ($!,$?);
    my $pid = wait();
    return if $pid == -1;
    $exit_codes{$pid} = $?;
    cleanup_child($pid);
};

sub system {
    # open3 closes <& handles
    open(local *TO_CHLD, '<&STDIN');
    my $pid = open3('<&TO_CHLD', '>&STDOUT', '>&STDERR', @_);
    return waitpid($pid, 0) == -1 ? delete($exit_codes{$pid}) : $?;
}

while(1){
    my $pid = fork();
    if ($pid == 0){
        ...
        exit 0;
    } else {
        ...
        system($command);
        ...
   }
}

• [PATCH] Attempt at improving the perlipc docs by Maik Hentsche
• Re: [PATCH] Attempt at improving the perlipc docs by Maik Hentsche
• Re: [PATCH] Attempt at improving the perlipc docs by Rafael Garcia-Suarez
• Re: [PATCH] Attempt at improving the perlipc docs by Leon Timmermans
• Re: [PATCH] Attempt at improving the perlipc docs by Maik Hentsche
• Re: [PATCH] Attempt at improving the perlipc docs by Eric Brine
• Re: [PATCH] Attempt at improving the perlipc docs by Maik Hentsche
• Re: [PATCH] Attempt at improving the perlipc docs by Steffen Schwigon
• Re: [PATCH] Attempt at improving the perlipc docs by Eric Brine
• Re: [PATCH] Attempt at improving the perlipc docs by Eric Brine
• Re: [PATCH] Attempt at improving the perlipc docs by Zefram