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From: momjian(at)svr1(dot)postgresql(dot)org (Bruce Momjian)
To: pgsql-committers(at)postgresql(dot)org
Subject: pgsql-server/src backend/libpq/pqsignal.c back ...
Date: 2004-04-12 16:19:18
Message-ID: 20040412161918.EF954D1C9C8@svr1.postgresql.org (view raw or flat)
Thread:
Lists: pgsql-committers
CVSROOT:	/cvsroot
Module name:	pgsql-server
Changes by:	momjian(at)svr1(dot)postgresql(dot)org	04/04/12 13:19:18

Modified files:
	src/backend/libpq: pqsignal.c 
	src/backend/port/win32: Makefile sema.c 
	src/backend/postmaster: pgstat.c postmaster.c 
	src/include    : miscadmin.h 
	src/include/libpq: pqsignal.h 
	src/include/port: win32.h 
	src/port       : pgsleep.c 
Added files:
	src/backend/port/win32: signal.c socket.c 

Log message:
	Here's an attempt at new socket and signal code for win32.
	
	It works on the principle of turning sockets into non-blocking, and then
	emulate blocking behaviour on top of that, while allowing signals to
	run. Signals are now implemented using an event instead of APCs, thus
	getting rid of the issue of APCs not being compatible with "old style"
	sockets functions.
	
	It also moves the win32 specific code away from pqsignal.h/c into
	port/win32, and also removes the "thread style workaround" of the APC
	issue previously in place.
	
	In order to make things work, a few things are also changed in pgstat.c:
	
	1) There is now a separate pipe to the collector and the bufferer. This
	is required because the pipe will otherwise only be signalled in one of
	the processes when the postmaster goes down. The MS winsock code for
	select() must have some kind of workaround for this behaviour, but I
	have found no stable way of doing that. You really are not supposed to
	use the same socket from more than one process (unless you use
	WSADuplicateSocket(), in which case the docs specifically say that only
	one will be flagged).
	
	2) The check for "postmaster death" is moved into a separate select()
	call after the main loop. The previous behaviour select():ed on the
	postmaster pipe, while later explicitly saying "we do NOT check for
	postmaster exit inside the loop".
	The issue was that the code relies on the same select() call seeing both
	the postmaster pipe *and* the pgstat pipe go away. This does not always
	happen, and it appears that useing WSAEventSelect() makes it even more
	common that it does not.
	Since it's only called when the process exits, I don't think using a
	separate select() call will have any significant impact on how the stats
	collector works.
	
	Magnus Hagander


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