From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Bill Studenmund <wrstuden(at)zembu(dot)com> |
Cc: | Tatsuo Ishii <t-ishii(at)sra(dot)co(dot)jp>, spshealy(at)yahoo(dot)com, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: SIGCHLD handler in Postgres C function. |
Date: | 2001-07-30 23:14:22 |
Message-ID: | 25436.996534862@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Bill Studenmund <wrstuden(at)zembu(dot)com> writes:
> I see three choices:
> 1) Change back to SIG_DFL for normal behavior. I think this will be fine
> as we run w/o problem on systems that lack this behavior. If
> turning off automatic child reaping would cause a problem, we'd
> have seen it already on the OSs which don't automatically reap
> children. Will a backend ever fork after it's started?
Backends never fork more backends --- but there are some places that
launch transient children and wait for them to finish. A non-transient
subprocess should always be launched by the postmaster, never by a
backend, IMHO.
> 2) Change to DFL around system() and then change back.
I think this is pretty ugly, and unnecessary.
> 3) Realize that ECHILD means that the child was auto-reaped (which is an
> ok think and, I think, will only happen if the child exited w/o
> error).
That's the behavior that's in place now, but I do not like it. We
should not need to code an assumption that "this error isn't really
an error" --- especially when it only happens on some platforms.
On a non-Linux kernel, an ECHILD failure really would be a failure,
and the existing code would fail to detect that there was a problem.
Bottom line: I like solution #1. Does anyone have an objection to it?
regards, tom lane
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