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Date:   Mon, 25 Jan 2021 08:39:03 +0000
From:   Christoph Hellwig <hch@infradead.org>
To:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc:     Christoph Hellwig <hch@infradead.org>, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
        Thomas Gleixner <tglx@linutronix.de>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH 3/3] blk-mq: Use llist_head for blk_cpu_done
Message-ID: <20210125083903.GB945284@infradead.org>
References: <20210123201027.3262800-1-bigeasy@linutronix.de>
 <20210123201027.3262800-4-bigeasy@linutronix.de>
 <20210125083012.GD942655@infradead.org>
 <20210125083204.ahddujk5m6njwbju@linutronix.de>
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On Mon, Jan 25, 2021 at 09:32:04AM +0100, Sebastian Andrzej Siewior wrote:
> On 2021-01-25 08:30:12 [+0000], Christoph Hellwig wrote:
> > > +static void blk_mq_complete_send_ipi(struct request *rq)
> > > +{
> > > +	struct llist_head *list;
> > > +	unsigned int cpu;
> > > +
> > > +	cpu = rq->mq_ctx->cpu;
> > > +	list = &per_cpu(blk_cpu_done, cpu);
> > > +	if (llist_add(&rq->ipi_list, list)) {
> > > +		INIT_CSD(&rq->csd, __blk_mq_complete_request_remote, rq);
> > > +		smp_call_function_single_async(cpu, &rq->csd);
> > > +	}
> > > +}
> > 
> > Nit: it would be nice to initialize cpu and list in the declaration
> > lines.
> 
> Why? They get initialized later.

Because:

	unsigned int cpu = rq->mq_ctx->cpu;
	struct llist_head *list = &per_cpu(blk_cpu_done, cpu);

is a lot easier to follow than:

	struct llist_head *list;
	unsigned int cpu;

	cpu = rq->mq_ctx->cpu;
	list = &per_cpu(blk_cpu_done, cpu);