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Date:   Wed, 4 Aug 2021 19:02:00 +0200
From:   Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To:     Jens Axboe <axboe@kernel.dk>
Cc:     Steven Rostedt <rostedt@goodmis.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Daniel Wagner <wagi@monom.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-rt-users@vger.kernel.org
Subject: Re: [ANNOUNCE] v5.14-rc4-rt4
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On 2021-08-04 10:57:11 [-0600], Jens Axboe wrote:
> > The spin_lock_irq() vs local_irq_disable() + spin_lock() is documented
> > in Documentation/locking/locktypes.rst.
> > That said I have no problem by carrying that patch in the RT-patchset
> > and revisit it later.
> 
> Right, I suspect that was added as a pre RT patch dump at some point.
> It's a newer thing. Is it actually possible to set PREEMPT_RT in the
> mainline kernel? Looks like it depends on ARCH_SUPPORTS_RT and nobody
> sets that.

Yes. It is upstream now. The documentation and CONFIG_PREEMPT_RT symbol.
The Kconfig symbol has already users outside of the -RT patch.

You can't enable it yet since we require a few things which are on their
way.

Having the symbol and the documentation helped to convince some people
:) 

> So I agree that just carrying your solution in the RT patchset is fine
> for now, we can revisit later.

Okay.

Sebastian