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Message-ID: <CABXOdTcKo=r9Yxj9KQEAdqgO5ok_4udak9x3ae7WEe_B7r5fZg@mail.gmail.com>
Date: Wed, 26 Jun 2019 13:12:10 -0700
From: Guenter Roeck <groeck@...gle.com>
To: Douglas Anderson <dianders@...omium.org>
Cc: Paolo Valente <paolo.valente@...aro.org>,
Jens Axboe <axboe@...nel.dk>,
Guenter Roeck <groeck@...omium.org>,
Nicolas Boichat <drinkcat@...omium.org>,
linux-block@...r.kernel.org,
linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] block, bfq: Init saved_wr_start_at_switch_to_srt in
unlikely case
On Wed, Jun 26, 2019 at 1:00 PM Douglas Anderson <dianders@...omium.org> wrote:
>
> Some debug code suggested by Paolo was tripping when I did reboot
> stress tests. Specifically in bfq_bfqq_resume_state()
> "bic->saved_wr_start_at_switch_to_srt" was later than the current
> value of "jiffies". A bit of debugging showed that
> "bic->saved_wr_start_at_switch_to_srt" was actually 0 and a bit more
> debugging showed that was because we had run through the "unlikely"
> case in the bfq_bfqq_save_state() function.
>
> Let's init "saved_wr_start_at_switch_to_srt" in the unlikely case to
> something sane.
>
> NOTE: this fixes no known real-world errors.
>
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> Reviewed-by: Paolo Valente <paolo.valente@...aro.org>
Reviewed-by: Guenter Roeck <groeck@...omium.org>
>
> ---
> Paolo said to add his Reviewed-by in https://crrev.com/c/1678756.
>
> block/bfq-iosched.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
> index 72840ebf953e..008c93d6b8d7 100644
> --- a/block/bfq-iosched.c
> +++ b/block/bfq-iosched.c
> @@ -2678,6 +2678,7 @@ static void bfq_bfqq_save_state(struct bfq_queue *bfqq)
> * to enjoy weight raising if split soon.
> */
> bic->saved_wr_coeff = bfqq->bfqd->bfq_wr_coeff;
> + bic->saved_wr_start_at_switch_to_srt = bfq_smallest_from_now();
> bic->saved_wr_cur_max_time = bfq_wr_duration(bfqq->bfqd);
> bic->saved_last_wr_start_finish = jiffies;
> } else {
> --
> 2.22.0.410.gd8fdbe21b5-goog
>
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