Hi Jakub,
On Mon, Feb 03, 2020 at 10:12:25AM -0800, Jakub Kicinski wrote:
> On Fri, 31 Jan 2020 19:20:07 +0530, Manivannan Sadhasivam wrote:
> > +/* From QRTR to MHI */
> > +static void qcom_mhi_qrtr_ul_callback(struct mhi_device *mhi_dev,
> > + struct mhi_result *mhi_res)
> > +{
> > + struct qrtr_mhi_dev *qdev = dev_get_drvdata(&mhi_dev->dev);
> > + struct qrtr_mhi_pkt *pkt;
> > + unsigned long flags;
> > +
> > + spin_lock_irqsave(&qdev->ul_lock, flags);
> > + pkt = list_first_entry(&qdev->ul_pkts, struct qrtr_mhi_pkt, node);
> > + list_del(&pkt->node);
> > + complete_all(&pkt->done);
> > +
> > + kref_put(&pkt->refcount, qrtr_mhi_pkt_release);
>
> Which kref_get() does this pair with?
>
> Looks like qcom_mhi_qrtr_send() will release a reference after
> completion, too.
>
Yikes, there is some issue here...
Acutally the issue is not in what you referred above but the overall kref
handling itself. Please see below.
kref_put() should be present in qcom_mhi_qrtr_ul_callback() as it will
decrement the refcount which got incremented in qcom_mhi_qrtr_send(). It
should be noted that kref_init() will fix the refcount to 1 and kref_get() will
increment to 2. So for properly releasing the refcount to 0, we need to call
kref_put() twice.
So if all goes well, the refcount will get decremented twice in
qcom_mhi_qrtr_ul_callback() as well as in qcom_mhi_qrtr_send() and we are good.
But, if the transfer has failed ie., when qcom_mhi_qrtr_ul_callback() doesn't
get called, then we are leaking the refcount. I need to rework the kref handling
code in next iteration.
Thanks for triggering this!
Regards,
Mani
> > + spin_unlock_irqrestore(&qdev->ul_lock, flags);
> > +}
