linux-kernel - Re: [PATCH RFC 10/14] block, bfq: add Early Queue Merge (EQM)

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Date:   Wed, 15 Mar 2017 10:56:25 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Paolo Valente <paolo.valente@...aro.org>, Tejun Heo <tj@...nel.org>
Cc:     Fabio Checconi <fchecconi@...il.com>,
        Arianna Avanzini <avanzini.arianna@...il.com>,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        ulf.hansson@...aro.org, linus.walleij@...aro.org,
        broonie@...nel.org, Mauro Andreolini <mauro.andreolini@...more.it>
Subject: Re: [PATCH RFC 10/14] block, bfq: add Early Queue Merge (EQM)

On 03/04/2017 09:01 AM, Paolo Valente wrote:
> @@ -6330,7 +7012,41 @@ static void bfq_rq_enqueued(struct bfq_data *bfqd, struct bfq_queue *bfqq,
>  
>  static void __bfq_insert_request(struct bfq_data *bfqd, struct request *rq)
>  {
> -	struct bfq_queue *bfqq = RQ_BFQQ(rq);
> +	struct bfq_queue *bfqq = RQ_BFQQ(rq), *new_bfqq;
> +
> +	/*
> +	 * An unplug may trigger a requeue of a request from the device
> +	 * driver: make sure we are in process context while trying to
> +	 * merge two bfq_queues.
> +	 */
> +	if (!in_interrupt()) {

What's the reason for this? Don't use in_interrupt() to guide any of
your decision making here.

-- 
Jens Axboe