Re: Backporting dwc3 gadget fixes

[Evan Green <evgreen@google.com>]

On Tue, Jan 29, 2019 at 2:22 AM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Wed, Jan 23, 2019 at 10:46:52AM -0800, Evan Green wrote:
> > Hi Felipe,
> > Well, I've only tried on the one device that has a dwc3 controller.
> > Given that the bug was "scheduling while atomic", the stack trace
> > always had dwc3_gadget_ep_dequeue doing the sleeping, and it only
> > happened when I had a gadget plugged in, I felt pretty solid that this
> > was the same bug.
> >
> > Also, Matthias pointed out I was looking at an older series when I was
> > figuring out which patches went together. Check my work, but the
> > series seems to be here:
> > https://patchwork.kernel.org/project/linux-usb/list/?series=42875
> >
> > The first 3 patches are already backported. Then there were a couple
> > extra I had missed before. So the complete set would look like:
> >
> > d53701067f04 usb: dwc3: gadget: check if dep->frame_number is still valid
> > 3451f6affaef usb: dwc3: gadget: remove unnecessary dev_info()
> > 1517265228b4 usb: dwc3: trace: log ep commands in hex
> > 25abad6a0584 usb: dwc3: gadget: return errors from __dwc3_gadget_start_isoc()
> > fec9095bdef4e usb: dwc3: gadget: remove wait_end_transfer
> > d4f1afe5e896c usb: dwc3: gadget: move requests to cancelled_list
> > d5443bbf5fc8f usb: dwc3: gadget: introduce cancelled_list
> > 7746a8dfb3f9c usb: dwc3: gadget: extract dwc3_gadget_ep_skip_trbs()
> > c3acd59014148 usb: dwc3: gadget: use num_trbs when skipping TRBs on ->dequeue()
> > 09fe1f8d7e2f4 usb: dwc3: gadget: track number of TRBs per request
> > 1a22ec6435806 usb: dwc3: gadget: combine unaligned and zero flags
> >
> > Though perhaps only the stuff up through "move requests to
> > cancelled_list" is the important stuff... Felipe might be able to say
> > better.
>
> Can someone send me a correct list of exactly what patches to commit, to
> what kernel tree(s), and in what order?  Ideally you would have also
> tested them yourself...
>
> As it is, this "random list of commits" doesn't make me feel good about
> backporting.

Ok here's my recommendation, in short form: cherry-pick
1dbcd8d42c02..fec9095bdef4 to 4.19.

Long form rationale below:
The series these fixes came from is this:
https://patchwork.kernel.org/project/linux-usb/list/?series=42875

The first three are already in stable. I recommend picking the below
commits, which I've listed in git log order, so the apply order would
be bottom-up:
fec9095bdef4e usb: dwc3: gadget: remove wait_end_transfer
d4f1afe5e896c usb: dwc3: gadget: move requests to cancelled_list
d5443bbf5fc8f usb: dwc3: gadget: introduce cancelled_list
7746a8dfb3f9c usb: dwc3: gadget: extract dwc3_gadget_ep_skip_trbs()
c3acd59014148 usb: dwc3: gadget: use num_trbs when skipping TRBs on ->dequeue()
09fe1f8d7e2f4 usb: dwc3: gadget: track number of TRBs per request
1a22ec6435806 usb: dwc3: gadget: combine unaligned and zero flags

The remaining commits of the series appear to me to fix a different
problem from the crash I'm seeing. Plus, this commit:
25abad6a0584 usb: dwc3: gadget: return errors from __dwc3_gadget_start_isoc()
won't apply cleanly without first taking this commit:
d92021f66063 usb: dwc3: Add workaround for isoc start transfer failure

The patches I'm recommending apply cleanly on linux-stable/linux-4.19.y.

For 4.14, the landscape has shifted around so much that these patches
don't apply cleanly. I was able to fix them up manually, and could
send that out if desired, but I'm not able to test chose changes.
-Evan