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

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Date:	Mon, 09 Mar 2015 11:00:58 +0100
From:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:	Mike Galbraith <umgwanakikbuti@...il.com>
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 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.

> 
> 	-Mike
> 

Sebastian
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