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

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Date:   Mon, 20 Dec 2021 16:49:16 -0300
From:   Wander Costa <wcosta@...hat.com>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     Wander Lairson Costa <wander@...hat.com>,
        open list <linux-kernel@...r.kernel.org>,
        Steven Rostedt <rostedt@...dmis.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 Mon, Dec 20, 2021 at 4:38 PM Jens Axboe <axboe@...nel.dk> wrote:
>
> On 12/20/21 12:28 PM, Wander Lairson Costa wrote:
> > The running_trace_lock protects running_trace_list and is acquired
> > within the tracepoint which implies disabled preemption. The spinlock_t
> > typed lock can not be acquired with disabled preemption on PREEMPT_RT
> > because it becomes a sleeping lock.
> > The runtime of the tracepoint depends on the number of entries in
> > running_trace_list and has no limit. The blk-tracer is considered debug
> > code and higher latencies here are okay.
>
> You didn't put a changelog in here. Was this one actually compiled? Was
> it runtime tested?

It feels like the changelog reached the inboxes after patch (at least
mine was so). Would you like that I send a v6 in the hope things
arrive in order?