[PATCH 3/3] dma-buf: nuke SW_SYNC debugfs files

[John Stultz]

On Thu, Jul 29, 2021 at 12:24 AM Daniel Vetter <daniel at ffwll.ch> wrote:
>
> On Thu, Jul 29, 2021 at 09:03:30AM +0200, Christian König wrote:
> > As we now knew controlling dma_fence synchronization from userspace is
> > extremely dangerous and can not only deadlock drivers but trivially also the
> > whole kernel memory management.
> >
> > Entirely remove this option. We now have in kernel unit tests to exercise the
> > dma_fence framework and it's containers.
> >
> > Signed-off-by: Christian König <christian.koenig at amd.com>
>
> There's also igts for this, and Android heavily uses this. So I'm not sure
> we can just nuke it.

Eeeeh... I don't think that's actually the case anymore. As of
android12-5.10 CONFIG_SW_SYNC is not turned on.
Further, Android is disabling debugfs in their kernels as it exposes
too much to userland.

That said, there still are some references to it:
  https://cs.android.com/android/platform/superproject/+/master:system/core/libsync/sync.c;l=416

But it looks like the actual users are only kselftest and igt?

Adding Alistair, Hridya and Sandeep in case they have more context.

thanks
-john