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Re: [HACKERS] [PATCHES] fork/exec patch

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Magnus Hagander <mha(at)sollentuna(dot)net>
Cc: Andrew Dunstan <andrew(at)dunslane(dot)net>,pgsql-hackers-win32 <pgsql-hackers-win32(at)postgresql(dot)org>
Subject: Re: [HACKERS] [PATCHES] fork/exec patch
Date: 2003-12-17 01:29:23
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers-win32
Having read through this massive thread, I concluded the CONNX signal
stuff is the way to go.  Where there any Win32 TODO items in there?  I
didn't see any.


Magnus Hagander wrote:
> >>>Isn't WaitForSingleObject() in effect a polling call?
> >>>    
> >>>
> >>It puts your thread to sleep, until it gets woken up by the handle
> >>you're waiting on being set to a signalled state.
> >>
> >>  
> >>
> >
> >Right. Just like select() puts your thread to sleep until one of its 
> >files is ready (or it times out).
> >
> >Do we have a terminology problem here?
> >
> >The point is that, unlike classic Unix signal programming, you need 
> >*something* that explicitly checks for the event. It could be 
> >a separate 
> >thread in a tight loop, which is what the CONNX code appears to do, or 
> >it could conceivably be something else in the main thread with a very 
> >short timeout.
> Yes, if you include the wait...() in the tight loop, which means it will
> spend 99.999% of it's time in sleeping state (kernel blocked). But yes,
> in some way it has to go back into the main thread. Either through some
> kind of polling or through exception. Unless the handlers are
> threadsafe.
> I know at least the SIGHUP handler in pgsql (backend/tcop/postgres.c)
> just sets a flag in the signal handler, which could be easily protected
> (this flag is polled in the main loop). The comments seem to indicate
> the idea that complex signal handlers = bad. I guess we need to check
> out the other signal handlers - if they're that easy, then it's a
> non-point and they can really easy be made thread-safe.
> //Magnus
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  Bruce Momjian                        |
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