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Re: [HACKERS] backend freezeing on win32 fixed (I hope ;-) )
- To: Horak Daniel <horak@mmp.plzen-city.cz>
- Subject: Re: [HACKERS] backend freezeing on win32 fixed (I hope ;-) )
- From: Tom Lane <tgl@sss.pgh.pa.us>
- Date: Mon, 16 Aug 1999 10:07:00 -0400
- cc: "'pgsql-hackers@postgreSQL.org'" <pgsql-hackers@postgreSQL.org>, "'cygwin@sourceware.cygnus.com'" <cygwin@sourceware.cygnus.com>, "'Joost Kraaijeveld'" <JKraaijeveld@askesis.nl>
Horak Daniel <horak@mmp.plzen-city.cz> writes:
> I think I have fixed the freezing of the postgres backend on Windows NT. Now
> it survives 5 regression test in a cycle with some concurrent connections
> during running the tests.
> It have looked like a problem with initializing the same semaphore for
> second time (they are "preinitialized" for performance reasons in
> InitProcGlobal() in storage/lmgr/proc.c)
They should never be "initialized a second time". And the preallocation
is *not* for performance reasons, it is to make sure we can actually get
enough semaphores (rather than dying under load when we fail to get the
N+1'st semaphore when starting the N+1'st backend).
> The fix (made for v6.5.1) is here:
> [ Fix consists of diking out preallocation of semaphores by postmaster ]
I do not like this patch one bit --- I think it is voodoo that doesn't
really have anything to do with the true problem. I don't know what
the true problem is, mind you, but I don't think this is the way to
fix it.
Is it possible that the CygWin environment doesn't have a correct
emulation of IPC semaphores, such that a sema allocated by one process
(the postmaster) is not available to other procs (the backends)?
That would explain preallocation not working --- but if that's it then
we have major problems in other places, since the code assumes that a
sema once allocated will remain available to later backends.
regards, tom lane
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