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

[Bhaumik Bhatt]

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.

> > @@ -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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