Re: Allow signal handlers to optionally use SA_SIGINFO information?

On 2014-11-10 09:50:17 -0500, Tom Lane wrote:
> Andres Freund <andres(at)2ndquadrant(dot)com> writes:
> > Posix provides information about the source of the signal when using
> > SA_SIGINFO style handlers via si_code/si_pid. That information has been
> > available for a *long* while
> > (c.f. http://pubs.opengroup.org/onlinepubs/7908799/xsh/signal.h.html)
>
> That does not mean that it exists on all the platforms we support;
> Windows in particular is likely to be an issue.

Given that we essentially use a named pipe to transport signals, it
shouldn't be too hard if we decide we need it.

> I concur with Heikki that you're probably solving this at the wrong
> end anyway, since the next question you'll be asking is *why* did
> process X send that signal.

I agree that that's the most useful thing for any specific situation
fully under our control. But generally I'd have more than once found it
useful to have the sender of a signal available - even if it's just
during debugging. I also previously would have liked to know where
INT/TERM are coming from - having the senders pid can be useful to
diagnose.

If we add it, it's surely nothing we ever are going to rely on - as you
say, there's portability issues. But printing it optionallY in a few
place at appropriate debug levels + having it available in signal
handlers during debugging sounds useful enough anyway to me.

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services