| Message ID | 1605723625-11206-1-git-send-email-bbhatt@codeaurora.org |
|---|---|
| State | New |
| Headers | show |
| Series | net: qrtr: Unprepare MHI channels during remove | expand |
On 2020-11-18 11:34 AM, Jeffrey Hugo wrote: > On 11/18/2020 12:14 PM, Loic Poulain wrote: >> >> >> Le mer. 18 nov. 2020 à 19:34, Jeffrey Hugo <jhugo@codeaurora.org >> <mailto:jhugo@codeaurora.org>> a écrit : >> >> On 11/18/2020 11:20 AM, Bhaumik Bhatt wrote: >> > Reset MHI device channels when driver remove is called due to >> > module unload or any crash scenario. This will make sure that >> > MHI channels no longer remain enabled for transfers since the >> > MHI stack does not take care of this anymore after the >> auto-start >> > channels feature was removed. >> > >> > Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org >> <mailto:bbhatt@codeaurora.org>> >> > --- >> > net/qrtr/mhi.c | 1 + >> > 1 file changed, 1 insertion(+) >> > >> > diff --git a/net/qrtr/mhi.c b/net/qrtr/mhi.c >> > index 7100f0b..2bf2b19 100644 >> > --- a/net/qrtr/mhi.c >> > +++ b/net/qrtr/mhi.c >> > @@ -104,6 +104,7 @@ static void qcom_mhi_qrtr_remove(struct >> mhi_device *mhi_dev) >> > struct qrtr_mhi_dev *qdev = >> dev_get_drvdata(&mhi_dev->dev); >> > >> > qrtr_endpoint_unregister(&qdev->ep); >> > + mhi_unprepare_from_transfer(mhi_dev); >> > dev_set_drvdata(&mhi_dev->dev, NULL); >> > } >> > >> > >> >> I admit, I didn't pay much attention to the auto-start being >> removed, >> but this seems odd to me. >> >> As a client, the MHI device is being removed, likely because of >> some >> factor outside of my control, but I still need to clean it up? >> This >> really feels like something MHI should be handling. >> >> >> I think this is just about balancing operations, what is done in probe >> should be undone in remove, so here channels are started in probe and >> stopped/reset in remove. > > I understand that perspective, but that doesn't quite match what is > going on here. Regardless of if the channel was started (prepared) in > probe, it now needs to be stopped in remove. That not balanced in all > cases > > Lets assume, in response to probe(), my client driver goes and creates > some other object, maybe a socket. In response to that socket being > opened/activated by the client of my driver, I go and start the mhi > channel. Now, normally, when the socket is closed/deactivated, I stop > the MHI channel. In this case, stopping the MHI channel in remove() > is unbalanced with respect to probe(), but is now a requirement. > > Now you may argue, I should close the object in response to remove, > which will then trigger the stop on the channel. That doesn't apply > to everything. For example, you cannot close an open file in the > kernel. You need to wait for userspace to close it. By the time that > happens, the mhi_dev is long gone I expect. > > So if, somehow, the client driver is the one causing the remove to > occur, then yes it should probably be the one doing the stop, but > that's a narrow set of conditions, and I think having that requirement > for all scenarios is limiting. It should be the client's responsibility to perform a clean-up though. We cannot assume that the remove() call was due to factors outside of the client's control at all times. You may not know if the remove() was due to device actually crashing or just an unbind/module unload. So, it would be better if you call it as the device should ideally not be left with a stale channel context. We had an issue where a client was issuing a driver unbind without unpreparing the MHI channels and without Loic's patch [1], we would not issue a channel RESET to the device resulting in incoming data to the host on those channels after host clean-up and an unmapped memory access and kernel panic. If MHI dev will be gone that NULL/status check must be present in something that userspace could potentially use. [1] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/drivers/bus/mhi?h=next-20201119&id=a7f422f2f89e7d48aa66e6488444a4c7f01269d5 Thanks, Bhaumik --- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project
On Wed, 18 Nov 2020 10:20:25 -0800 Bhaumik Bhatt wrote: > Reset MHI device channels when driver remove is called due to > module unload or any crash scenario. This will make sure that > MHI channels no longer remain enabled for transfers since the > MHI stack does not take care of this anymore after the auto-start > channels feature was removed. > > Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org> Patch seems reasonable, Mani are you taking it or should I? Bhaumik would you mind adding a Fixes tag to be clear where the issue was introduced?
On Thu, Nov 19, 2020 at 09:10:46PM -0800, Jakub Kicinski wrote: > On Wed, 18 Nov 2020 10:20:25 -0800 Bhaumik Bhatt wrote: > > Reset MHI device channels when driver remove is called due to > > module unload or any crash scenario. This will make sure that > > MHI channels no longer remain enabled for transfers since the > > MHI stack does not take care of this anymore after the auto-start > > channels feature was removed. > > > > Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org> > > Patch seems reasonable, Mani are you taking it or should I? > Since I already picked up one qrtr patch, makese sense to pick this also. > Bhaumik would you mind adding a Fixes tag to be clear where > the issue was introduced? This is due to the MHI auto-start change which just got queued into mhi-next. I don't think we need a Fixes tag. Jakub, can you please provide your ack so that I can take it? Thanks, Mani
On Thu, Nov 19, 2020 at 10:18:28PM -0800, Jakub Kicinski wrote: > On Fri, 20 Nov 2020 11:45:12 +0530 Manivannan Sadhasivam wrote: > > Jakub, can you please provide your ack so that I can take it? > > Sure: > > Acked-by: Jakub Kicinski <kuba@kernel.org> Patch applied to mhi-ath11k-immutable. Thanks, Mani
diff --git a/net/qrtr/mhi.c b/net/qrtr/mhi.c index 7100f0b..2bf2b19 100644 --- a/net/qrtr/mhi.c +++ b/net/qrtr/mhi.c @@ -104,6 +104,7 @@ static void qcom_mhi_qrtr_remove(struct mhi_device *mhi_dev) struct qrtr_mhi_dev *qdev = dev_get_drvdata(&mhi_dev->dev); qrtr_endpoint_unregister(&qdev->ep); + mhi_unprepare_from_transfer(mhi_dev); dev_set_drvdata(&mhi_dev->dev, NULL); }
Reset MHI device channels when driver remove is called due to module unload or any crash scenario. This will make sure that MHI channels no longer remain enabled for transfers since the MHI stack does not take care of this anymore after the auto-start channels feature was removed. Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org> --- net/qrtr/mhi.c | 1 + 1 file changed, 1 insertion(+)