RFR: 8034944: (process) Improve subprocess handling on Solaris

[Martin Buchholz]

On Sun, Mar 23, 2014 at 2:34 AM, Martin Buchholz <martinrb at google.com>wrote:

>
> We have also thought about whether having reaper threads is necessary.
>  The Unix rule is that child processes should be waited for, and some
> thread needs to do that.  There's no way to wait for a set of child pids,
> or to specify a "completion handler".  Well, you might be able to get the
> newish waitid() to do what you want, but it looks like it's not sufficient
> when java is running inside a process that might do independent subprocess
> creation outside of the JVM.
>
>
Actually, I take it back.  With sufficient work, it looks like you can get
SIGCHLD to give you pid information in siginfo_t si_pid, and that can be
used to trigger the reaping.  It looks like waitpid is "async-signal-safe",
so we can call it from our signal handler.

While we're at it we can fix SIGCHLD handling to do signal chaining, as
with other signals.