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Re: Win32 signals code, take two

From: "Merlin Moncure" <merlin(dot)moncure(at)rcsonline(dot)com>
To: "Magnus Hagander" <mha(at)sollentuna(dot)net>
Cc: "pgsql-hackers-win32" <pgsql-hackers-win32(at)postgresql(dot)org>
Subject: Re: Win32 signals code, take two
Date: 2004-01-19 14:54:25
Message-ID: 303E00EBDD07B943924382E153890E5434AA67@cuthbert.rcsinc.local (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers-win32
Magnus Hagander wrote:
> > Magnus Hagander wrote:
> > > Here's an updated version of the proposed win32 signals
> > code, with the
> > > following main changes:
> >
> > One small possible revision to consider:  As I read the code,
> > all manipulation to pg_signal_queue is inside a
> > CriticalSection, and it is only set (> 0) when there are
> > pending signals.
> >
> > ISTM that pg_queue_signal can abort without calling
> > QueueUserAPC pg_signal_queue is already set.  This will keep
> > the dispatch function from getting called extra times.
> > Paranoia statement
> >
> > pg_signal_queue = 0;
> >
> > could possibly be added at the end of the dispatch.
> No, I don't think it can't. Consider delayed signals. When leaving the
> dispatch function, pg_signal_queue may very well be != 0. Only
> (pg_signal_queue & ~pg_signal_mask) should be zero. bad.

> Also, I think it's best if the mask is checked upon signal *delivery*,
> not queueing. The signal could be blocked when delivered and
> on delivery. If we never queue a APC in this case, the signal will be
> lost. But we *could* do the check in pg_signal_queue, but then against
> (pg_signal_queue &~ pg_signal_mask).

Right...that is safer.  I still think there may be a more sophisticated
check in there...if any executable signal is already pending, then you
can count that you are either in a dispatch or that dispatch is already


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Subject: Re: Microsoft releses Services for Unix
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Subject: Re: Win32 signals code, take two

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