linux-kernel - Re: [PATCH v4 10/10] IB/mlx5: Simplify completion into a wait

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Date:   Wed, 2 Nov 2016 17:59:24 +0200
From:   Leon Romanovsky <leon@...nel.org>
To:     Binoy Jayan <binoy.jayan@...aro.org>
Cc:     Sagi Grimberg <sagi@...mberg.me>,
        Doug Ledford <dledford@...hat.com>,
        Sean Hefty <sean.hefty@...el.com>,
        Hal Rosenstock <hal.rosenstock@...il.com>,
        Arnd Bergmann <arnd@...db.de>, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 10/10] IB/mlx5: Simplify completion into a wait_event

On Sun, Oct 30, 2016 at 11:17:57PM +0200, Sagi Grimberg wrote:
>
>
> On 27/10/16 09:59, Binoy Jayan wrote:
> >Convert the completion 'mlx5_ib_umr_context:done' to a wait_event as it
> >just waits for the return value to be filled.

On top of Sagi's response, I'm failing to understand why it is needed.
Can you elaborate more about it?

> >
> >Signed-off-by: Binoy Jayan <binoy.jayan@...aro.org>
> >---
> > drivers/infiniband/hw/mlx5/mlx5_ib.h | 2 +-
> > drivers/infiniband/hw/mlx5/mr.c      | 9 +++++----
> > include/rdma/ib_verbs.h              | 1 +
> > 3 files changed, 7 insertions(+), 5 deletions(-)
> >
> >diff --git a/drivers/infiniband/hw/mlx5/mlx5_ib.h b/drivers/infiniband/hw/mlx5/mlx5_ib.h
> >index de31b5f..cf496b5 100644
> >--- a/drivers/infiniband/hw/mlx5/mlx5_ib.h
> >+++ b/drivers/infiniband/hw/mlx5/mlx5_ib.h
> >@@ -524,7 +524,7 @@ struct mlx5_ib_mw {
> > struct mlx5_ib_umr_context {
> > 	struct ib_cqe		cqe;
> > 	enum ib_wc_status	status;
> >-	struct completion	done;
> >+	wait_queue_head_t	wq;
> > };
> >
> > struct umr_common {
> >diff --git a/drivers/infiniband/hw/mlx5/mr.c b/drivers/infiniband/hw/mlx5/mr.c
> >index dfaf6f6..49ff2af 100644
> >--- a/drivers/infiniband/hw/mlx5/mr.c
> >+++ b/drivers/infiniband/hw/mlx5/mr.c
> >@@ -846,14 +846,14 @@ static void mlx5_ib_umr_done(struct ib_cq *cq, struct ib_wc *wc)
> > 		container_of(wc->wr_cqe, struct mlx5_ib_umr_context, cqe);
> >
> > 	context->status = wc->status;
> >-	complete(&context->done);
> >+	wake_up(&context->wq);
> > }
> >
> > static inline void mlx5_ib_init_umr_context(struct mlx5_ib_umr_context *context)
> > {
> > 	context->cqe.done = mlx5_ib_umr_done;
> >-	context->status = -1;
> >-	init_completion(&context->done);
> >+	context->status = IB_WC_STATUS_NONE;
> >+	init_waitqueue_head(&context->wq);
> > }
> >
> > static inline int mlx5_ib_post_send_wait(struct mlx5_ib_dev *dev,
> >@@ -873,7 +873,8 @@ static inline int mlx5_ib_post_send_wait(struct mlx5_ib_dev *dev,
> > 	if (err) {
> > 		mlx5_ib_warn(dev, "UMR post send failed, err %d\n", err);
> > 	} else {
> >-		wait_for_completion(&umr_context.done);
> >+		wait_event(umr_context.wq,
> >+			   umr_context.status != IB_WC_STATUS_NONE);
>
> How is this simpler?
>
>
> > enum ib_wc_status {
> >+	IB_WC_STATUS_NONE = -1,
> > 	IB_WC_SUCCESS,
> > 	IB_WC_LOC_LEN_ERR,
> > 	IB_WC_LOC_QP_OP_ERR,
> >
>
> Huh? Where did this bogus status came from? IMHO, this is polluting
> the verbs interface for no good reason at all, sorry.
> --
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