Re: /proc/<pid>/{cwd, root} links to <defunct> for cygrunsrv, daemons, and shells

[Corinna Vinschen <corinna-cygwin@cygwin.com>]

On Apr  7 13:34, Brian Inglis wrote:
> ISTM anomalous that for cygrunsrv, daemons, cron processes, and shells
> /proc/<pid>/{cwd,root} have bad symlinks to "<defunct>", normally a process
> or exe status:
> 
> /proc/732/exe   -> /usr/bin/cygrunsrv
> /proc/732/root  -> <defunct>
> /proc/732/cwd   -> <defunct>
> |  /proc/733/exe   -> /usr/sbin/cygserver
>  ->/proc/733/root  -> <defunct>
>    /proc/733/cwd   -> <defunct>
> /proc/740/exe   -> /usr/bin/cygrunsrv
> /proc/740/root  -> <defunct>
> /proc/740/cwd   -> <defunct>
> |  /proc/741/exe   -> /usr/sbin/syslog-ng
>  ->/proc/741/root  -> <defunct>
>    /proc/741/cwd   -> <defunct>
> /proc/748/exe   -> /usr/bin/cygrunsrv
> /proc/748/root  -> <defunct>
> /proc/748/cwd   -> <defunct>
> |  /proc/749/exe   -> /usr/sbin/cron
>  ->/proc/749/root  -> <defunct>
>    /proc/749/cwd   -> <defunct>
>    |  /proc/2080/exe  -> /usr/sbin/cron
>     ->/proc/2080/root -> <defunct>
>       /proc/2080/cwd  -> <defunct>
>       |  /proc/2082/exe  -> /usr/bin/bash
>        ->/proc/2082/root -> <defunct>
>          /proc/2082/cwd  -> <defunct>
> 
> Should we consider changing that to root "/", or nothing, null, or something
> meaningful?

That's typically a permission problem.  On Linux you get something like

  ls: cannot read symbolic link '/proc/1/cwd': Permission denied

But on Cygwin the content of those links require to open the processes'
signal pipe and send/receive a message containing the information.  I
didn't look into the code for a while but it seems we don't check why we
couldn't connect to a process to fetch the info.  IIRC the current
fhandler_process framework doesn't have a way to communicate that
info.

If you want to change that, feel free!


Corinna