Re: [PATCH 2/3] spi: pxa2xx: Fix controller unregister order

[Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>]

On Wed, May 27, 2020 at 09:09:17PM +0900, Tsuchiya Yuto wrote:
> I tried a kernel built with the prerequisite patch to this series + all
> of patches in this series on top of v5.7-rc7 (with Arch Linux config
> + olddefconfig).
> 
> Current situations on 5.7-rc7 with Arch Linux config + olddefconfig
> (without applying this series):
> - I can reproduce the touch input crashing (surface3-spi) I mentioned
>   in bugzilla [1] only after s2idle.
> - all the other situations are the same as described in that bugzilla;
>   I see NULL pointer dereference [2] after touch input crashing then try
>   to unload only spi_pxa2xx_platform module.
> 
> So, the steps to test that I did with this series applied are:
> 1. go into s2idle then resume from s2idle
> 2. make a touch input then surface3-spi reports that "SPI transfer
>    timed out" repeatedly and no longer responds to any touch input
> 3. try to unload only spi_pxa2xx_platform module and see if the NULL
>    pointer dereference no longer occurs
> 
> and I can confirm that I no longer see the NULL pointer dereference.
> Thanks!

Thank you very much for testing!

> On 5/26/20 5:22 PM, Andy Shevchenko wrote:
> > On Tue, May 26, 2020 at 09:39:13AM +0200, Lukas Wunner wrote:
> >> On Mon, May 25, 2020 at 04:21:43PM +0300, Andy Shevchenko wrote:
> >>> Tsuchiya Yuto, I'm going to apply this series as preparatory to my
> >>> WIP patch in topic/spi/reload branch in my kernel tree on GitHub,
> >>> so, it would be possible to see if this + my patch fixes crashes
> >>> on removal. Though, please test this separately from my stuff to
> >>> clarify if it fixes or not issue you have seen.
> >> You also need to cherry-pick commit 84855678add8 ("spi: Fix controller
> >> unregister order") from spi/for-next onto your topic/spi/reload branch
> >> for reloading to work correctly.
> >>
> >> Alternatively, rebase your topic/spi/reload branch and redo the merge
> >> from spi/for-next.  (You've merged spi/for-next into your branch on
> >> May 14, but the commit was applied by Mark on May 20.)
> > Ah, right. Will do it soon.
> 
> I also built a kernel against your branch topic/spi/reload
> (permalink: https://github.com/andy-shev/linux/tree/55cb78d5a752). The
> result is the same as only applying this series; so, to fix the NULL pointer
> dereference that I mentioned in bugzilla [2], only this series is required.
> 
> Also, I want to make sure that what you tried in that branch is fixing
> the NULL pointer dereference on spi_pxa2xx_platform module removal when
> touch input crashed, not fixing the touch input crashing itself?

Yes, my aim was to fix the SPI module reload issue. While the applied patch
from Lukas does a huge improvement, there are still issues with ordering (you
probably will never see them, though it's still possible based on the code).

So, as far as I understood, the touch still able to come into position where
it's not anymore responsive. Is it correct?

> [1] https://bugzilla.kernel.org/show_bug.cgi?id=206403
> [2] https://bugzilla.kernel.org/show_bug.cgi?id=206403#c1

-- 
With Best Regards,
Andy Shevchenko