From: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
To: Chris Lew <clew@codeaurora.org>
Cc: Jakub Kicinski <kuba@kernel.org>,
gregkh@linuxfoundation.org, arnd@arndb.de,
smohanad@codeaurora.org, jhugo@codeaurora.org,
kvalo@codeaurora.org, bjorn.andersson@linaro.org,
hemantk@codeaurora.org, linux-arm-msm@vger.kernel.org,
linux-kernel@vger.kernel.org,
"David S. Miller" <davem@davemloft.net>,
netdev@vger.kernel.org
Subject: Re: [PATCH v2 14/16] net: qrtr: Add MHI transport layer
Date: Tue, 11 Feb 2020 09:20:20 +0530 [thread overview]
Message-ID: <20200211035020.GA3358@Mani-XPS-13-9360> (raw)
In-Reply-To: <53018abf-4bc9-1ddb-0be5-a9a3b9871a33@codeaurora.org>
Hi Chris,
On Thu, Feb 06, 2020 at 04:14:19PM -0800, Chris Lew wrote:
>
> On 2/4/2020 12:19 AM, Manivannan Sadhasivam wrote:
> > 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);
> > > > +}
>
> Hi Mani,
>
> I'm not sure if this was changed in your patches but MHI is supposed to give a
> ul_callback() for any packet that is successfully queued. In the case of the
> transfer failing, the ul_callback() should still be called so there should
> be no refcount leaking. It is an essential assumption I made, if that no longer
> holds true then the entire driver needs to be reworked.
>
Your assumption is correct. Only when the packet gets queued into the transfer
ring, the ul_xfer_cb will be called irrespective of the transfer state (success
or failure). But when the mhi_queue_transfer() returns even before queuing any
packet, then we need to decrease the refcount in the error path.
Please correct me if I'm wrong.
Thanks,
Mani
> Thanks,
> Chris
>
> --
>
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project
next prev parent reply other threads:[~2020-02-11 3:50 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-31 13:49 [PATCH v2 00/16] Add MHI bus support Manivannan Sadhasivam
2020-01-31 13:49 ` [PATCH v2 01/16] docs: Add documentation for MHI bus Manivannan Sadhasivam
2020-01-31 22:57 ` Jeffrey Hugo
2020-01-31 13:49 ` [PATCH v2 02/16] bus: mhi: core: Add support for registering MHI controllers Manivannan Sadhasivam
2020-02-06 16:56 ` Greg KH
2020-02-11 19:11 ` Manivannan Sadhasivam
2020-02-11 19:22 ` Greg KH
2020-02-13 15:22 ` Manivannan Sadhasivam
2020-02-06 16:57 ` Greg KH
2020-02-11 18:41 ` Manivannan Sadhasivam
2020-02-11 19:20 ` Greg KH
2020-02-13 15:20 ` Manivannan Sadhasivam
2020-02-13 15:34 ` Greg KH
2020-02-13 15:48 ` Manivannan Sadhasivam
2020-02-13 15:53 ` Greg KH
2020-02-14 16:41 ` Jeffrey Hugo
2020-02-17 5:27 ` Manivannan Sadhasivam
2020-02-17 11:45 ` Greg KH
2020-02-17 11:53 ` Manivannan Sadhasivam
2020-02-17 11:59 ` Greg KH
2020-02-17 13:04 ` Manivannan Sadhasivam
2020-02-17 14:15 ` Greg KH
2020-02-17 16:04 ` Arnd Bergmann
2020-02-17 16:32 ` Greg KH
2020-02-17 17:50 ` Manivannan Sadhasivam
2020-02-06 17:08 ` Jeffrey Hugo
2020-01-31 13:49 ` [PATCH v2 03/16] bus: mhi: core: Add support for registering MHI client drivers Manivannan Sadhasivam
2020-01-31 23:00 ` Jeffrey Hugo
2020-01-31 13:49 ` [PATCH v2 04/16] bus: mhi: core: Add support for creating and destroying MHI devices Manivannan Sadhasivam
2020-02-06 16:16 ` Jeffrey Hugo
2020-01-31 13:49 ` [PATCH v2 05/16] bus: mhi: core: Add support for ringing channel/event ring doorbells Manivannan Sadhasivam
2020-02-06 20:14 ` Jeffrey Hugo
2020-01-31 13:49 ` [PATCH v2 06/16] bus: mhi: core: Add support for PM state transitions Manivannan Sadhasivam
2020-02-06 20:15 ` Jeffrey Hugo
2020-01-31 13:50 ` [PATCH v2 07/16] bus: mhi: core: Add support for basic PM operations Manivannan Sadhasivam
2020-02-06 20:15 ` Jeffrey Hugo
2020-01-31 13:50 ` [PATCH v2 08/16] bus: mhi: core: Add support for downloading firmware over BHIe Manivannan Sadhasivam
2020-02-06 20:15 ` Jeffrey Hugo
2020-01-31 13:50 ` [PATCH v2 09/16] bus: mhi: core: Add support for downloading RDDM image during panic Manivannan Sadhasivam
2020-02-06 16:41 ` Jeffrey Hugo
2020-02-06 20:17 ` Jeffrey Hugo
2020-01-31 13:50 ` [PATCH v2 10/16] bus: mhi: core: Add support for processing events from client device Manivannan Sadhasivam
2020-02-06 20:16 ` Jeffrey Hugo
2020-01-31 13:50 ` [PATCH v2 11/16] bus: mhi: core: Add support for data transfer Manivannan Sadhasivam
2020-02-06 20:16 ` Jeffrey Hugo
2020-02-17 16:13 ` Arnd Bergmann
2020-02-17 16:47 ` Manivannan Sadhasivam
2020-02-18 5:51 ` Manivannan Sadhasivam
2020-02-18 14:34 ` Arnd Bergmann
2020-01-31 13:50 ` [PATCH v2 12/16] bus: mhi: core: Add uevent support for module autoloading Manivannan Sadhasivam
2020-02-06 20:16 ` Jeffrey Hugo
2020-01-31 13:50 ` [PATCH v2 13/16] MAINTAINERS: Add entry for MHI bus Manivannan Sadhasivam
2020-02-03 10:16 ` Andy Shevchenko
2020-02-04 7:05 ` Manivannan Sadhasivam
2020-01-31 13:50 ` [PATCH v2 14/16] net: qrtr: Add MHI transport layer Manivannan Sadhasivam
2020-02-03 18:12 ` Jakub Kicinski
2020-02-04 8:19 ` Manivannan Sadhasivam
2020-02-07 0:14 ` Chris Lew
2020-02-11 3:50 ` Manivannan Sadhasivam [this message]
2020-02-12 1:01 ` Chris Lew
2020-01-31 13:50 ` [PATCH v2 15/16] net: qrtr: Do not depend on ARCH_QCOM Manivannan Sadhasivam
2020-01-31 13:50 ` [PATCH v2 16/16] soc: qcom: Do not depend on ARCH_QCOM for QMI helpers Manivannan Sadhasivam
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