linux-kernel - Re: [PATCH v5 1/1] blktrace: switch trace spinlock to a raw spinlock

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Message-ID: <4d110c2a-2e70-8fc1-a16e-cd576c646a39@kernel.dk>
Date:   Mon, 20 Dec 2021 16:45:57 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Wander Costa <wcosta@...hat.com>,
        Wander Lairson Costa <wander@...hat.com>,
        open list <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        "open list:BLOCK LAYER" <linux-block@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: Re: [PATCH v5 1/1] blktrace: switch trace spinlock to a raw spinlock

On 12/20/21 4:30 PM, Steven Rostedt wrote:
> On Mon, 20 Dec 2021 13:49:47 -0700
> Jens Axboe <axboe@...nel.dk> wrote:
> 
>> Alright, fair enough, mistakes happen. I think the patch looks fine, my
>> main dislike is that it's Yet Another things that needs special RT
>> handling. But I guess that's how it is...
> 
> It's not really "yet another thing". That's because in general tracing
> needs special RT handling (and a lot of other special handling, not
> just RT). blktrace falls under the tracing category, and this just
> falls under one more thing to make tracing work with RT.

This isn't the first patch like this I've applied. I'm not saying this
is an issue with tracing, just that it's another one of these "spinlocks
are now preemptible/sleeping with RT" and that necessitates changes like
this.

-- 
Jens Axboe