+ Adrian
On Mon, 18 Oct 2021 at 15:56, Sebastian Andrzej Siewior
<bigeasy@xxxxxxxxxxxxx> wrote:
>
> The completion callback for the sdhci-pci device is invoked from a
> kworker.
> I couldn't identify in which context is mmc_blk_mq_req_done() invoke but
> the remaining caller are from invoked from preemptible context. Here it
> would make sense to complete the request directly instead scheduling
> ksoftirqd for its completion.
>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Thanks for working on this!
I have looped in Adrian, to allow him to provide us with his input too.
> ---
> drivers/mmc/core/block.c | 22 ++++++++++++++--------
> 1 file changed, 14 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
> index 431af5e8be2f8..7d6b43fe52e8a 100644
> --- a/drivers/mmc/core/block.c
> +++ b/drivers/mmc/core/block.c
> @@ -2051,7 +2051,8 @@ static void mmc_blk_mq_dec_in_flight(struct mmc_queue *mq, struct request *req)
> mmc_put_card(mq->card, &mq->ctx);
> }
>
> -static void mmc_blk_mq_post_req(struct mmc_queue *mq, struct request *req)
> +static void mmc_blk_mq_post_req(struct mmc_queue *mq, struct request *req,
> + bool can_sleep)
> {
> struct mmc_queue_req *mqrq = req_to_mmc_queue_req(req);
> struct mmc_request *mrq = &mqrq->brq.mrq;
> @@ -2063,10 +2064,14 @@ static void mmc_blk_mq_post_req(struct mmc_queue *mq, struct request *req)
> * Block layer timeouts race with completions which means the normal
> * completion path cannot be used during recovery.
> */
> - if (mq->in_recovery)
> + if (mq->in_recovery) {
> mmc_blk_mq_complete_rq(mq, req);
> - else if (likely(!blk_should_fake_timeout(req->q)))
> - blk_mq_complete_request(req);
> + } else if (likely(!blk_should_fake_timeout(req->q))) {
> + if (can_sleep)
> + blk_mq_complete_request_direct(req, mmc_blk_mq_complete);
> + else
> + blk_mq_complete_request(req);
> + }
>
> mmc_blk_mq_dec_in_flight(mq, req);
> }
> @@ -2087,7 +2092,7 @@ void mmc_blk_mq_recovery(struct mmc_queue *mq)
>
> mmc_blk_urgent_bkops(mq, mqrq);
>
> - mmc_blk_mq_post_req(mq, req);
> + mmc_blk_mq_post_req(mq, req, true);
> }
>
> static void mmc_blk_mq_complete_prev_req(struct mmc_queue *mq,
> @@ -2106,7 +2111,7 @@ static void mmc_blk_mq_complete_prev_req(struct mmc_queue *mq,
> if (prev_req)
> *prev_req = mq->complete_req;
> else
> - mmc_blk_mq_post_req(mq, mq->complete_req);
> + mmc_blk_mq_post_req(mq, mq->complete_req, true);
>
> mq->complete_req = NULL;
>
> @@ -2178,7 +2183,8 @@ static void mmc_blk_mq_req_done(struct mmc_request *mrq)
> mq->rw_wait = false;
> wake_up(&mq->wait);
>
> - mmc_blk_mq_post_req(mq, req);
> + /* context unknown */
> + mmc_blk_mq_post_req(mq, req, false);
So it seems we would benefit from knowing the context here, right?
At this point, what you suggest seems like a reasonable way forward
(assuming atomic context), but in a next step we could potentially add
a non-atomic helper function for mmc host drivers to call, when that
is suitable. Would that make sense you think?
> }
>
> static bool mmc_blk_rw_wait_cond(struct mmc_queue *mq, int *err)
> @@ -2238,7 +2244,7 @@ static int mmc_blk_mq_issue_rw_rq(struct mmc_queue *mq,
> err = mmc_start_request(host, &mqrq->brq.mrq);
>
> if (prev_req)
> - mmc_blk_mq_post_req(mq, prev_req);
> + mmc_blk_mq_post_req(mq, prev_req, true);
>
> if (err)
> mq->rw_wait = false;
Kind regards
Uffe
