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To: cygwin AT cygwin DOT com
From: Achim Gratz <Stromeko AT nexgo DOT de>
Subject: Re: [TEST] sqlite3-3.7.17-1 (Cygwin 1.7.19 locking feature)
Date: Thu, 06 Jun 2013 20:17:12 +0200
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References: <51ACF886 DOT 10301 AT etr-usa DOT com> <51AD3BB4 DOT 2010601 AT acm DOT org>	<20130604084128 DOT GB19572 AT calimero DOT vinschen DOT de>	<20130604093749 DOT GA32667 AT calimero DOT vinschen DOT de>	<51AF9A32 DOT 2030706 AT etr-usa DOT com>	<20130606172218 DOT GD13320 AT calimero DOT vinschen DOT de>
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Corinna Vinschen writes:
> In theory this scenario could be worked around in Cygwin by bookkeeping
> the present locks, plus a piece of code which unlocks all existing locks
> in the given range when a lock or unlock request is coming in.  However,
> the really dismal fact is, that an unlock before a lock would never be
> atomic.  If the F_SETLK request unlocks an existing lock and then
> another process gets a lock in the requested range, the first process
> ends up with a failed fcntl call and no lock at all.

Thanks for the explanation, I'm beginning to see what the backoff / retry
code in SQLite on WIndows is supposed to be doing (hopefully).


Regards,
Achim.
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