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

Bhaumik Bhatt
2021-07-21T18:07:13Z

On 2021-07-21 10:52 AM, hemantk@codeaurora.org wrote:
> On 2021-07-20 18:42, Bhaumik Bhatt wrote:
>> A dl callback can be received anytime after mhi_prepare_for_transfer
>> has been called. There is a window where the callback may happen
>> before the probe initializes the qrtr_mhi_dev state. Move the
>> mhi_prepare_for_transfer call after the registering the endpoint.
>>
>> Once moved, 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: a2e2cc0dbb11 ("net: qrtr: Start MHI channels during init")
>> Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
>> ---
>> net/qrtr/mhi.c | 20 +++++++++++++++-----
>> 1 file changed, 15 insertions(+), 5 deletions(-)
>>
>> diff --git a/net/qrtr/mhi.c b/net/qrtr/mhi.c
>> index 29b4fa3..22b0395 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 ready;
>> };
>>
>> /* From MHI to QRTR */
>> @@ -50,6 +51,10 @@ static int qcom_mhi_qrtr_send(struct qrtr_endpoint
>> *ep, struct sk_buff *skb)
>> struct qrtr_mhi_dev *qdev = container_of(ep, struct qrtr_mhi_dev,
>> ep);
>> int rc;
>>
>> + rc = wait_for_completion_interruptible(&qdev->ready);
>> + if (rc)
>> + goto free_skb;
>> +
>> if (skb->sk)
>> sock_hold(skb->sk);
>>
>> @@ -78,11 +83,6 @@ static int qcom_mhi_qrtr_probe(struct mhi_device
>> *mhi_dev,
>> struct qrtr_mhi_dev *qdev;
>> int rc;
>>
>> - /* start channels */
>> - rc = mhi_prepare_for_transfer(mhi_dev, MHI_CH_INBOUND_ALLOC_BUFS);
>> - if (rc)
>> - return rc;
>> -
>> qdev = devm_kzalloc(&mhi_dev->dev, sizeof(*qdev), GFP_KERNEL);
>> if (!qdev)
>> return -ENOMEM;
> would it be good to init completion variable here (call
> init_completion) ?
You mean just before setting qdev->mhi_dev? I don't see why that would
make a difference
mainly because the qcom_mhi_qrtr_send() will only happen after endpoint
is
registered and DL xfer cb will also only come in after we have prepared
the
channels and completed ready with dev_data already set.

>> @@ -90,12 +90,22 @@ 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->ready);
>>
>
>>
>> return 0;

Thanks,
Bhaumik
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