xffm - xfsamba4 broken in 5-stable?

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Date: Tue, 31 May 2005 20:39:47 +0300
To: freebsd-stable@freebsd.org

I've had the same problem and I think everybody using recent FreeBSD has
it. The culprit seems to be the following line in tubo.c:

if (kill(PID,SIGCONT) == 0) return TRUE;

I am not sure about other OS's and what POSIX mandates in this case, but
FreeBSD 5.4 allows to send signals to child processes that have exited
but have not been reaped by parent. They show up in ps like this:
 5320 pd Z+ 0:00,05 <defunct>

Because of the quoted line of code nmblookup processes are never reaped
and xfsamba4 goes into infinite loop.

Probably FreeBSD 5.1 had problems with respect to the described
situation (it was an experimental release after all) and that line was a
work-around for some FreeBSD bug, but now it actually breaks things.

Removing that line fixed xfsamba4 for me, but I encountered another
problem after that, my PDC (NT4) doesn't respond to the following
request (Samba3 client):
        nmblookup -A <master browser ip>
so instead I had to use
        nmblookup -M -S -- -
and this made xfsamba4 perfectly well.

P.S. just found the following about POSIX, kill, and defunct child
processes:

http://www.opengroup.org/onlinepubs/009695399/functions/kill.html

Existing implementations vary on the result of a kill() with pid
indicating an inactive process (a terminated process that has not been
waited for by its parent). Some indicate success on such a call (subject
to permission checking), while others give an error of [ESRCH]. Since
the definition of process lifetime in this volume of IEEE Std
1003.1-2001 covers inactive processes, the [ESRCH] error as described is
inappropriate in this case. In particular, this means that an
application cannot have a parent process check for termination of a
particular child with kill(). (Usually this is done with the null
signal; this can be done reliably with waitpid().)

-- 
Andriy Gapon
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