linux-kernel - Re: [PATCH 2/2] mutex: Apply adaptive spinning on mutex

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Message-ID: <1301058727.14261.174.camel@gandalf.stny.rr.com>
Date:	Fri, 25 Mar 2011 09:12:07 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Andrey Kuzmin <andrey.v.kuzmin@...il.com>
Cc:	Tejun Heo <tj@...nel.org>, Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Chris Mason <chris.mason@...cle.com>,
	linux-kernel@...r.kernel.org, linux-btrfs@...r.kernel.org
Subject: Re: [PATCH 2/2] mutex: Apply adaptive spinning on mutex_trylock()

On Fri, 2011-03-25 at 14:13 +0300, Andrey Kuzmin wrote:
> Turning try_lock into indefinitely spinning one breaks its semantics,
> so deadlock is to be expected. But what's wrong in this scenario if
> try_lock spins a bit before giving up? 

Because that will cause this scenario to spin that "little longer"
always, and introduce latencies that did not exist before. Either the
solution does not break this scenario, or it should not go in.

-- Steve


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