linux-kernel - Re: [PATCH 1/2] rpmsg: glink: change rx work queue type

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Date:   Sat, 15 Jul 2023 14:44:59 -0700
From:   Bjorn Andersson <andersson@...nel.org>
To:     Manikanta Mylavarapu <quic_mmanikan@...cinc.com>
Cc:     agross@...nel.org, konrad.dybcio@...aro.org,
        mathieu.poirier@...aro.org, linux-arm-msm@...r.kernel.org,
        linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org,
        quic_srichara@...cinc.com, quic_sjaganat@...cinc.com,
        quic_kathirav@...cinc.com, quic_anusha@...cinc.com,
        quic_varada@...cinc.com
Subject: Re: [PATCH 1/2] rpmsg: glink: change rx work queue type

On Wed, Jun 07, 2023 at 05:47:30PM +0530, Manikanta Mylavarapu wrote:
> In case of heavy cpu load, rx worker thread
> not able to get cpu slot because it's bound
> to kernel global work queue.
> 
> Glink client drivers will return timeout
> error if they didn't receive response
> within stipulated duration. Changing rx
> work queue type to UNBOUND workqueue
> ensures rx worker thread will be executed
> as early as possible.
> 

I'm guessing that you're referring to the fact that incoming intent
requests (GLINK_CMD_RX_INTENT_REQ) are handled in the rx_worker. But I
shouldn't have to guess, please improve your commit message to be
slightly more specific.

Could we/should we handle the intent requests differently?

Please also use 75 character long lines in your commit message.

> Signed-off-by: Manikanta Mylavarapu <quic_mmanikan@...cinc.com>
> ---
>  drivers/rpmsg/qcom_glink_native.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/rpmsg/qcom_glink_native.c b/drivers/rpmsg/qcom_glink_native.c
> index 1beb40a1d3df..6f9a439e5046 100644
> --- a/drivers/rpmsg/qcom_glink_native.c
> +++ b/drivers/rpmsg/qcom_glink_native.c
> @@ -81,6 +81,7 @@ struct glink_core_rx_intent {
>   * @rx_pipe:	pipe object for receive FIFO
>   * @tx_pipe:	pipe object for transmit FIFO
>   * @rx_work:	worker for handling received control messages
> + * @rx_wq:	work queue of rx_work
>   * @rx_lock:	protects the @rx_queue
>   * @rx_queue:	queue of received control messages to be processed in @rx_work
>   * @tx_lock:	synchronizes operations on the tx fifo
> @@ -100,6 +101,7 @@ struct qcom_glink {
>  	struct qcom_glink_pipe *tx_pipe;
>  
>  	struct work_struct rx_work;
> +	struct workqueue_struct *rx_wq;
>  	spinlock_t rx_lock;
>  	struct list_head rx_queue;
>  
> @@ -822,7 +824,7 @@ static int qcom_glink_rx_defer(struct qcom_glink *glink, size_t extra)
>  	list_add_tail(&dcmd->node, &glink->rx_queue);
>  	spin_unlock(&glink->rx_lock);
>  
> -	schedule_work(&glink->rx_work);
> +	queue_work(glink->rx_wq, &glink->rx_work);
>  	qcom_glink_rx_advance(glink, sizeof(dcmd->msg) + extra);
>  
>  	return 0;
> @@ -1665,6 +1667,8 @@ static void qcom_glink_cancel_rx_work(struct qcom_glink *glink)
>  	/* cancel any pending deferred rx_work */
>  	cancel_work_sync(&glink->rx_work);
>  
> +	destroy_workqueue(glink->rx_wq);
> +
>  	list_for_each_entry_safe(dcmd, tmp, &glink->rx_queue, node)
>  		kfree(dcmd);
>  }
> @@ -1750,6 +1754,10 @@ struct qcom_glink *qcom_glink_native_probe(struct device *dev,
>  	INIT_WORK(&glink->rx_work, qcom_glink_work);
>  	init_waitqueue_head(&glink->tx_avail_notify);
>  
> +	glink->rx_wq = alloc_workqueue("glink_rx_wq", WQ_UNBOUND, 1);

Please see the description in e.g. 56310520308a ("soc: qcom: qmi: Use
alloc_ordered_workqueue() to create ordered workqueues")

Regards,
Bjorn

> +	if (!glink->rx_wq)
> +		return ERR_PTR(-ENOMEM);
> +
>  	spin_lock_init(&glink->idr_lock);
>  	idr_init(&glink->lcids);
>  	idr_init(&glink->rcids);
> -- 
> 2.17.1
>