linux-kernel - Re: [RFD/RFC PATCH 0/8] Towards implementing proxy execution

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Date:   Tue, 9 Oct 2018 14:35:58 +0200
From:   Juri Lelli <juri.lelli@...hat.com>
To:     Daniel Bristot de Oliveira <bristot@...hat.com>
Cc:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        peterz@...radead.org, mingo@...hat.com, rostedt@...dmis.org,
        tglx@...utronix.de, linux-kernel@...r.kernel.org,
        luca.abeni@...tannapisa.it, claudio@...dence.eu.com,
        tommaso.cucinotta@...tannapisa.it, alessio.balsini@...il.com,
        will.deacon@....com, andrea.parri@...rulasolutions.com,
        dietmar.eggemann@....com, patrick.bellasi@....com,
        henrik@...tad.us, linux-rt-users@...r.kernel.org
Subject: Re: [RFD/RFC PATCH 0/8] Towards implementing proxy execution

On 09/10/18 13:56, Daniel Bristot de Oliveira wrote:
> On 10/9/18 12:51 PM, Sebastian Andrzej Siewior wrote:
> >> The main concerns I have with the current approach is that, being based
> >> on mutex.c, it's both
> >>
> >>  - not linked with futexes
> >>  - not involving "legacy" priority inheritance (rt_mutex.c)
> >>
> >> I believe one of the main reasons Peter started this on mutexes is to
> >> have better coverage of potential problems (which I can assure everybody
> >> it had). I'm not yet sure what should we do moving forward, and this is
> >> exactly what I'd be pleased to hear your opinions on.
> > wasn't the idea that once it works to get rid of rt_mutex?

Looks like it was (see Peter's reply).

> As far as I know, it is. But there are some additional complexity
> involving a -rt version of this patch, for instance:
> 
> What should the protocol do if the thread migrating is with migration
> disabled?
> 
> The side effects of, for instance, ignoring the migrate_disable() would
> add noise for the initial implementation... too much complexity at once.
> 
> IMHO, once it works in the non-rt, it will be easier to do the changes
> needed to integrate it with -rt.
> 
> Thoughts?

Makes sense to me. Maybe we should just still keep in mind eventual
integration, so that we don't take decisions we would regret.