Date: Sun, 28 Oct 2007 22:48:33 +0000
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Matthew Wilcox <matthew@wil.cx>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>,
       "J. Bruce Fields" <bfields@fieldses.org>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       linux-kernel@vger.kernel.org, "George G. Davis" <gdavis@mvista.com>,
       Andrew Morton <akpm@linux-foundation.org>,
       linux-fsdevel@vger.kernel.org
Subject: Re: [RFC, PATCH] locks: remove posix deadlock detection
Message-ID: <20071028224833.66dc4243@the-village.bc.nu>
In-Reply-To: <20071028224157.GC32359@parisc-linux.org>
References: <20071017185157.GC3785@mvista.com>
	<20071018185759.GU3785@mvista.com>
	<20071026170750.GC13033@fieldses.org>
	<20071026224707.GO13033@fieldses.org>
	<20071028173136.GA16905@fieldses.org>
	<20071028174321.GB16905@fieldses.org>
	<20071028182732.GK27248@parisc-linux.org>
	<20071028184052.49abd092@the-village.bc.nu>
	<20071028201101.GA32359@parisc-linux.org>
	<1193608230.7561.11.camel@heimdal.trondhjem.org>
	<20071028224157.GC32359@parisc-linux.org>
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> Bzzt.  You get a false deadlock with multiple threads like so:
> 
> Thread A of task B takes lock 1
> Thread C of task D takes lock 2
> Thread C of task D blocks on lock 1
> Thread E of task B blocks on lock 2

The spec and SYSV certainly ignore threading in this situation and you
know that perfectly well (or did in 2004)
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