Re: [PATCH] net: qrtr: mhi: synchronize qrtr and mhi preparation

Manivannan Sadhasivam
2024-11-07T11:27:40Z

On Mon, Nov 04, 2024 at 05:29:37PM -0800, Chris Lew wrote:
> From: Bhaumik Bhatt <bbhatt@codeaurora.org>
>
> The call to qrtr_endpoint_register() was moved before
> mhi_prepare_for_transfer_autoqueue() to prevent a case where a dl
> callback can occur before the qrtr endpoint is registered.
>
> Now the reverse can happen where qrtr will try to send a packet
> before the channels are prepared. Add a wait in the sending path to
> ensure the channels are prepared before trying to do a ul transfer.
>
> Fixes: 68a838b84eff ("net: qrtr: start MHI channel after endpoit creation")
> Reported-by: Johan Hovold <johan@kernel.org>
> Closes: https://lore.kernel.org/linux-arm-msm/ZyTtVdkCCES0lkl4@hovoldconsulting.com/
> Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
> Signed-off-by: Chris Lew <quic_clew@quicinc.com>

I think we need to have the check in 'mhi_queue()' instead of waiting for the
channels in client drivers. Would it be a problem if qrtr returns -EAGAIN from
qcom_mhi_qrtr_send() instead of waiting for the channel?

- Mani

> ---
> net/qrtr/mhi.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/net/qrtr/mhi.c b/net/qrtr/mhi.c
> index 69f53625a049..5b7268868bbd 100644
> --- a/net/qrtr/mhi.c
> +++ b/net/qrtr/mhi.c
> @@ -15,6 +15,7 @@ struct qrtr_mhi_dev {
> struct qrtr_endpoint ep;
> struct mhi_device *mhi_dev;
> struct device *dev;
> + struct completion prepared;
> };
>
> /* From MHI to QRTR */
> @@ -53,6 +54,10 @@ static int qcom_mhi_qrtr_send(struct qrtr_endpoint *ep, struct sk_buff *skb)
> if (skb->sk)
> sock_hold(skb->sk);
>
> + rc = wait_for_completion_interruptible(&qdev->prepared);
> + if (rc)
> + goto free_skb;
> +
> rc = skb_linearize(skb);
> if (rc)
> goto free_skb;
> @@ -85,6 +90,7 @@ static int qcom_mhi_qrtr_probe(struct mhi_device *mhi_dev,
> qdev->mhi_dev = mhi_dev;
> qdev->dev = &mhi_dev->dev;
> qdev->ep.xmit = qcom_mhi_qrtr_send;
> + init_completion(&qdev->prepared);
>
> dev_set_drvdata(&mhi_dev->dev, qdev);
> rc = qrtr_endpoint_register(&qdev->ep, QRTR_EP_NID_AUTO);
> @@ -97,6 +103,7 @@ static int qcom_mhi_qrtr_probe(struct mhi_device *mhi_dev,
> qrtr_endpoint_unregister(&qdev->ep);
> return rc;
> }
> + complete_all(&qdev->prepared);
>
> dev_dbg(qdev->dev, "Qualcomm MHI QRTR driver probed\n");
>
>
> ---
> base-commit: 1ffec08567f426a1c593e038cadc61bdc38cb467
> change-id: 20241104-qrtr_mhi-dfec353030af
>
> Best regards,
> --
> Chris Lew <quic_clew@quicinc.com>
>

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