linux-kernel - Re: [PATCH 2/3] locking: ww_mutex: Allow to use rt

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Message-ID: <1425898264.9329.10.camel@gmail.com>
Date:	Mon, 09 Mar 2015 11:51:04 +0100
From:	Mike Galbraith <umgwanakikbuti@...il.com>
To:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:	Maarten Lankhorst <maarten.lankhorst@...onical.com>,
	linux-kernel@...r.kernel.org,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH 2/3] locking: ww_mutex: Allow to use rt_mutex instead of
 mutex for the baselock

On Mon, 2015-03-09 at 11:00 +0100, Sebastian Andrzej Siewior wrote:
> On 03/06/2015 06:50 PM, Mike Galbraith wrote:
> > On Fri, 2015-03-06 at 13:36 +0100, Sebastian Andrzej Siewior wrote:
> >> On 03/06/2015 01:16 PM, Maarten Lankhorst wrote:
> >>
> >>>> Okay so what I the point made here? It is only about the config option,
> >>>> right? What are the preferences here:
> >>>> [ ] yes, the way it is now
> >>> Is my personal preference, but I'm not a locking expert(TM).
> >>
> >> Lets see what Mike says. I currently don't see any reason for people to
> >> switch between both implementations except for testing. And if it
> >> remains hidden then nobody changing code ww_mutex tests against
> >> rt_mutex. That way there is hope :)
> > 
> > I don't see much point in an all or nothing config option, it'll just
> 
> it could be used for testing. My hope here is that if someone changes
> something within ww_mutex they test it ob both implementations.
> 
> > sit idle.  If folks can use them where they see fit, they might just do
> > that.  We have mutex/rtmutex, so why not ww_mutex/rt_ww_mutex?  Looks
> > like a natural extension to me.
> 
> And why would they need it? I would assume that this would only confuse
> them. And if (for $reason) they need PI they will (most likely) need it
> for everything not just one lock.

Why do both mutex and rtmutex then exist one might ask? ;-)  No big deal
either way though, it's not like it becomes immutable once applied.

	-Mike

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