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

[hemantk]

On 2021-07-21 11:07, Bhaumik Bhatt wrote:
> On 2021-07-21 10:52 AM, hemantk@xxxxxxxxxxxxxx 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@xxxxxxxxxxxxxx>
> > > ---
> > >  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; ?
> > > @@ -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