linux-kernel - Re: [RFC][PATCH RT 0/3] RT: Fix trylock deadlock without msleep() hack

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Message-ID: <20150905082626.00a20902@gandalf.local.home>
Date:	Sat, 5 Sep 2015 08:26:26 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org,
	linux-rt-users <linux-rt-users@...r.kernel.org>,
	Carsten Emde <C.Emde@...dl.org>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	John Kacur <jkacur@...hat.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Clark Williams <clark.williams@...il.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [RFC][PATCH RT 0/3] RT: Fix trylock deadlock without msleep()
 hack

On Sat, 5 Sep 2015 14:04:57 +0200
Ingo Molnar <mingo@...nel.org> wrote:

 
> So why not do:
> 
> 	lock(B);
> 	if (!trylock(A)) {
> 		unlock(B);
> 		lock(A);
> 		lock(B);
> 	}
> 
> ?
> 
> Or, if this can be done, why didn't we do:
> 
> 	lock(A);
> 	lock(B);
> 
> to begin with?
> 
> i.e. I'm not sure the problem is properly specified.

Yeah, this is actually the solution I came up with before. I misread
what Thomas wrote. His is slightly different.

-- Steve
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