linux-kernel - Re: [RFC, PATCH] locks: remove posix deadlock detection

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Message-Id: <1193608230.7561.11.camel@heimdal.trondhjem.org>
Date:	Sun, 28 Oct 2007 17:50:30 -0400
From:	Trond Myklebust <trond.myklebust@....uio.no>
To:	Matthew Wilcox <matthew@....cx>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	"J. Bruce Fields" <bfields@...ldses.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	"George G. Davis" <gdavis@...sta.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-fsdevel@...r.kernel.org
Subject: Re: [RFC, PATCH] locks: remove posix deadlock detection


On Sun, 2007-10-28 at 14:11 -0600, Matthew Wilcox wrote:
> On Sun, Oct 28, 2007 at 06:40:52PM +0000, Alan Cox wrote:
> > so we need to fix the bugs - the lock usage and the looping. At that
> > point it merely becomes a performance concern to those who use it, which
> > is the proper behaviour. If you want a faster non-checking one use
> > flock(), or add another flag that is a Linux "don't check for deadlock"
> 
> You can't fix the false EDEADLK detection without solving the halting
> problem.  Best of luck with that.

I can see that it would be difficult to do efficiently, but basically,
this boils down to finding a circular path in a graph. That is hardly an
unsolvable issue...

Trond

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