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References: <20211220192827.38297-1-wander@redhat.com> <8340efc7-f922-fb8c-772c-de72cefe3470@kernel.dk>
In-Reply-To: <8340efc7-f922-fb8c-772c-de72cefe3470@kernel.dk>
From:   Wander Costa <wcosta@redhat.com>
Date:   Mon, 20 Dec 2021 16:49:16 -0300
Message-ID: <CAAq0SUn_Nru1NTyzgjB9ETsaM46bgDRf3DTa+Z9sG-c8yjuQdw@mail.gmail.com>
Subject: Re: [PATCH v5 1/1] blktrace: switch trace spinlock to a raw spinlock
To:     Jens Axboe <axboe@kernel.dk>
Cc:     Wander Lairson Costa <wander@redhat.com>,
        open list <linux-kernel@vger.kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ingo Molnar <mingo@redhat.com>,
        "open list:BLOCK LAYER" <linux-block@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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On Mon, Dec 20, 2021 at 4:38 PM Jens Axboe <axboe@kernel.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?