Re: Shepherd does not recycle zombie processes

[Carlo Zancanaro]

On Wed, Nov 09 2016, Ludovic Courtès wrote
> Could you run shepherd in “strace -f” and see where the SIGCHLD 
> signals go?

I don't really know how to read strace's output (and there's a lot 
of it), but sometimes it gives a line like this:

    --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_KILLED, 
    si_pid=10496, si_status=SIGTERM, si_utime=142, si_stime=22} 
    ---

and sometimes it gives a line like this:

   [pid 10465] --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_KILLED, 
   si_pid=10556, si_status=SIGTERM, si_utime=84, si_stime=16} ---

If it has the [pid xxxxx] prefix then the signal is handled 
properly and the child process is reaped. If there's no prefix 
then a zombie process is left behind. (The pid in the prefix is 
the pid of the forked daemon process.)

Using my example init.scm file I have found that if I run `herd 
restart sleep` repeatedly and quickly (< 1 second) then it will 
consistently reap the processes. If I delay for more than about a 
second between runs then it will fail to reap the old process. 
(With strace attached this time is extended to a few seconds.)

Carlo

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