[radvd-devel-l] Race in PID file creation and daemonizing

[Reuben Hawkins]

Libdaemon sounds interesting.  Let's go that route. 

Sent from my iPhone

On Apr 4, 2012, at 4:38 AM, Petr Pisar <ppisar at redhat.com> wrote:

> Hello,
> 
> I've been reported <https://bugzilla.redhat.com/show_bug.cgi?id=664783> there
> is race between deamonizing and creating PID file.
> 
> Current code is:
> 
>    if (get_debuglevel() == 0) {
> 
>        if (daemonize) {
>            /* Detach from controlling terminal */
>            if (daemon(0, 0) < 0)
>                perror("daemon");
>        }
>    }
> 
>    write_pid_file(pidfile);
> 
> Which allows exiting executed radvd process before the PID file is created and
> filled with a PID number.
> 
> This can cause troubles to init scripts which wait for the process or inspect
> the PID file. (E.g. /etc/init.d/radvd start; /etc/init.d/radvd status.)
> 
> I'd like to fix it.
> 
> The daemon(3) function must be replaced with something which can synchronize
> PID file writing to daemonization.
> 
> I'm thinking about manual implementation (pipe, fork, setsid, fork, exit,
> synchronize through pipe, write PID file, exit) or using libdaemon library for
> that purpose. Which way is acceptable for radvd maintainer?
> 
> -- Petr
> -- 
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