User-space notification of process end

[Glen Turner <glen.turner@aarnet.edu.au>]

Hi,

I am writing a application which needs to know fairly
promptly if a daemon has died.  I'd prefer not to
alter the daemon source code or to run the program
as a non-daemon child of a daemon watcher process.

I tried using fnctl(..., F_NOTIFY, ...) as
follows

  f = open("/proc/123", O_RDONLY);
  signal(SIGIO, handler);
  fcntl(f, F_NOTIFY, DN_DELETE | DN_RENAME);
  F_ZERO(&f_set);
  F_SET(f, &f_set);
  select(1, NULL, NULL, &f_set, NULL);

hoping I'd see the /proc/<processid>/* files being
removed at process end.

But procfs doesn't seem to support fnctl(.., F_NOTIFY, ...)
for parameters other than DN_ACCESS.  This doesn't seem
to be limited to my code (the dnotify program, which has
much better signal handling, has the same behavior).

Suggestions, particularly ones which don't require polling
for the existence of the watched process, are welcome.

uname -r says 2.4.22-1.2149.nptl, which is the latest
Fedora Core 1 kernel.  I'm willing to try 2.6 if that
supports F_NOTIFY on /proc.

Thanks,
Glen

-- 
Glen Turner         Tel: (08) 8303 3936 or +61 8 8303 3936 
Network Engineer          Email: glen.turner@aarnet.edu.au
Australian Academic & Research Network   www.aarnet.edu.au