linux-kernel - Re: Question on mutex code

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Message-ID: <1426381746.28068.70.camel@stgolabs.net>
Date:	Sat, 14 Mar 2015 18:09:06 -0700
From:	Davidlohr Bueso <dave@...olabs.net>
To:	Matthias Bonne <lemonlime51@...il.com>
Cc:	Yann Droneaud <ydroneaud@...eya.com>,
	kernelnewbies@...nelnewbies.org, linux-kernel@...r.kernel.org,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: Question on mutex code

On Sat, 2015-03-14 at 18:03 -0700, Davidlohr Bueso wrote:
> Good analysis, but not quite accurate for one simple fact: mutex
> trylocks _only_ use fastpaths (obviously just depend on the counter
> cmpxchg to 0), so you never fallback to the slowpath you are mentioning,
> thus the race is non existent. Please see the arch code.

For debug we use the trylock slowpath, but so does everything else, so
again you cannot hit this scenario.

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