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

Bhaumik Bhatt
2021-07-22T19:50:45Z

On 2021-07-22 12:04 PM, Bhaumik Bhatt wrote:
> On 2021-07-21 03:27 PM, hemantk@codeaurora.org wrote:
>> On 2021-07-21 11:07, Bhaumik Bhatt wrote:
>>> 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.
>> looks like qcom_mhi_qrtr_send is not going to get called directly. i
>> was thinking
>> what if this api is called before init_completion() returns. if it is
>> only possible
>> through ep.xmit call back only, can you move it right above
>> qdev->ep.xmit = qcom_mhi_qrtr_send; ?
>>>
> Ah. OK. I see your point. I will do that and upload a v2.
>
On second thought, this is not required because the ep.xmit() will not
be called
until the qrtr_endpoint_register() is done.

So this version should be fine IMO.

>>>>> @@ -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
>>> ---
>>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
>>> Forum,
>>> a Linux Foundation Collaborative Project
>>
>> Thanks,
>> Hemant
>> ---
>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
>> Forum,
>> a Linux Foundation Collaborative Project
>
> Thanks,
> Bhaumik
> ---
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
> Forum,
> a Linux Foundation Collaborative Project

Thanks,
Bhaumik
---
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
Forum,
a Linux Foundation Collaborative Project