linux-kernel - Re: [ANNOUNCE] v5.14-rc4-rt4

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Message-ID: <c3fa07d1-a3c4-6775-f419-4875eb41bc88@kernel.dk>
Date:   Wed, 4 Aug 2021 10:05:39 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Daniel Wagner <wagi@...om.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-rt-users@...r.kernel.org,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [ANNOUNCE] v5.14-rc4-rt4

On 8/4/21 9:57 AM, Sebastian Andrzej Siewior wrote:
> On 2021-08-04 09:49:48 [-0600], Jens Axboe wrote:
>>
>> That'd work on non-RT as well, but it makes it worse on non-RT as well with
>> the irq enable/disable dance. While that's not the end of the world, would
>> be nice to have a solution that doesn't sacrifice anything, yet doesn't
>> make RT unhappy.
> 
> There were plans to make local_irq_disable() mostly a nop (similar to
> what ppc64 does). But I have no idea what happened. I hope that work
> gets picked up.

So what do you propose in the interim? As far as io_uring is concerned,
it's not a _huge_ deal to do the IRQ dance, but it does bother me that
we're making things slightly worse for the mainline kernel just to make
the out-of-tree patches happy.

-- 
Jens Axboe