Re: exec creating zombie processes

The problem is, when there is a timeout, your parent process is waiting. Since you interrupt the wait, the zombie is never reaped.

Instead of adding another wait, why not just set $SIG{CHLD} = 'IGNORE';?

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Re^2: exec creating zombie processes by ikegami (Patriarch) on Feb 14, 2011 at 22:05 UTC
Cause it complicates things. First, that wouldn't work. You'd have to change the existing `waitpid` to `sleep`. You'd end up with: `{ local $SIG{CHLD} = 'IGNORE'; ... launch child ... if (sleep(20)) { kill(KILL => $child_pid); # Wait for child to die before restoring $SIG{CHLD}. # Unlikely race condition. while (kill(0, $child_pid)) { sleep(1) or last; } } }` [download] There are side-effects to using $SIG{CHLD} = 'IGNORE'. One can't know the exit code of one's children, one can't use `system`, backticks, `open '-\|'` or `open '\|-'`, and one needs to worry about `EINTR`.	[reply] [d/l] [select]

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Re^2: exec creating zombie processes
by ikegami (Patriarch) on Feb 14, 2011 at 22:05 UTC

Cause it complicates things. First, that wouldn't work. You'd have to change the existing waitpid to sleep. You'd end up with:

{
   local $SIG{CHLD} = 'IGNORE';

   ... launch child ...

   if (sleep(20)) {
      kill(KILL => $child_pid);

      # Wait for child to die before restoring $SIG{CHLD}.
      # Unlikely race condition.
      while (kill(0, $child_pid)) {
         sleep(1) or last;
      }
   }
}
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There are side-effects to using $SIG{CHLD} = 'IGNORE'.

One can't know the exit code of one's children,
one can't use system, backticks, open '-|' or open '|-', and
one needs to worry about EINTR.

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