linux-kernel - Re: [PATCH v8 03/15] futex: Add basic infrastructure for local task local hash.

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Message-ID: <Z6XVLqexaKZr0cy1@jlelli-thinkpadt14gen4.remote.csb>
Date: Fri, 7 Feb 2025 10:41:02 +0100
From: Juri Lelli <juri.lelli@...hat.com>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org,
	André Almeida <andrealmeid@...lia.com>,
	Darren Hart <dvhart@...radead.org>,
	Davidlohr Bueso <dave@...olabs.net>, Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Valentin Schneider <vschneid@...hat.com>,
	Waiman Long <longman@...hat.com>
Subject: Re: [PATCH v8 03/15] futex: Add basic infrastructure for local task
 local hash.

Hi,

On 05/02/25 09:39, Sebastian Andrzej Siewior wrote:
> On 2025-02-04 11:34:47 [+0100], Peter Zijlstra wrote:

...

> > Anyway, none of this solves anything when a process has both an active
> > RT part and an active !RT part (which isn't uncommon AFAICT).
> > 
> > Then the RT bits will still get interference from the !RT bits. Do we
> > want to complicate things and consider that?
> 
> I don't think so. The active and inactive are common but it is still the
> same process so you can expect it. The ugly part is when it is an
> entirely different task and it is random which one it is.

Not entirely sure we are thinking about the same situation, but it looks
like we have cases of RT tasks that are affected by the underlying issue
this set is about because they make use of libraries. So, in this case
we have a cross-process (RT/!RT) situation that I am not sure we can
address sanely. What do you think?

Thanks,
Juri