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From: John Stultz <john.stultz@linaro.org>
To: Daniel Vetter <daniel@ffwll.ch>
Cc: "Christian König" <ckoenig.leichtzumerken@gmail.com>,
	"Gustavo Padovan" <gustavo@padovan.org>,
	dri-devel <dri-devel@lists.freedesktop.org>,
	"moderated list:DMA BUFFER SHARING FRAMEWORK"
	<linaro-mm-sig@lists.linaro.org>,
	linux-media <linux-media@vger.kernel.org>,
	"Alistair Delva" <adelva@google.com>,
	"Hridya Valsaraju" <hridya@google.com>,
	"Sandeep Patil" <sspatil@google.com>
Subject: Re: [PATCH 3/3] dma-buf: nuke SW_SYNC debugfs files
Date: Thu, 29 Jul 2021 21:52:19 -0700	[thread overview]
Message-ID: <CALAqxLVN7RVz3+z1ZvkRHeb2=Y4KbpbTOw-8St0D+Lzt5U-cFw@mail.gmail.com> (raw)
In-Reply-To: <YQJXi2JNZdH5DaR2@phenom.ffwll.local>

On Thu, Jul 29, 2021 at 12:24 AM Daniel Vetter <daniel@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@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

WARNING: multiple messages have this Message-ID (diff)
From: John Stultz <john.stultz@linaro.org>
To: Daniel Vetter <daniel@ffwll.ch>
Cc: "Alistair Delva" <adelva@google.com>,
	"Sandeep Patil" <sspatil@google.com>,
	"Christian König" <ckoenig.leichtzumerken@gmail.com>,
	dri-devel <dri-devel@lists.freedesktop.org>,
	"moderated list:DMA BUFFER SHARING FRAMEWORK"
	<linaro-mm-sig@lists.linaro.org>,
	"Gustavo Padovan" <gustavo@padovan.org>,
	"Hridya Valsaraju" <hridya@google.com>,
	linux-media <linux-media@vger.kernel.org>
Subject: Re: [PATCH 3/3] dma-buf: nuke SW_SYNC debugfs files
Date: Thu, 29 Jul 2021 21:52:19 -0700	[thread overview]
Message-ID: <CALAqxLVN7RVz3+z1ZvkRHeb2=Y4KbpbTOw-8St0D+Lzt5U-cFw@mail.gmail.com> (raw)
In-Reply-To: <YQJXi2JNZdH5DaR2@phenom.ffwll.local>

On Thu, Jul 29, 2021 at 12:24 AM Daniel Vetter <daniel@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@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

  parent reply	other threads:[~2021-07-30  4:52 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-29  7:03 [PATCH 1/3] dma-buf: nuke seqno-fence Christian König
2021-07-29  7:03 ` [PATCH 2/3] dma-buf: nuke DMA_FENCE_TRACE macros Christian König
2021-07-29  7:22   ` Daniel Vetter
2021-07-29  7:22     ` Daniel Vetter
2021-07-29  7:24     ` Christian König
2021-07-29  7:24       ` Christian König
2021-07-29  7:03 ` [PATCH 3/3] dma-buf: nuke SW_SYNC debugfs files Christian König
2021-07-29  7:23   ` Daniel Vetter
2021-07-29  7:23     ` Daniel Vetter
2021-07-29  8:38     ` Christian König
2021-07-29  8:38       ` Christian König
2021-07-29  9:03       ` Daniel Vetter
2021-07-29  9:03         ` Daniel Vetter
2021-07-29 10:21         ` Christian König
2021-07-29 10:21           ` Christian König
2021-07-29 11:59           ` Daniel Vetter
2021-07-29 11:59             ` Daniel Vetter
2021-07-29 12:25             ` Christian König
2021-07-29 12:25               ` Christian König
2021-07-29 12:31               ` Daniel Vetter
2021-07-29 12:31                 ` Daniel Vetter
2021-07-30  4:52     ` John Stultz [this message]
2021-07-30  4:52       ` John Stultz
2021-07-30 20:46       ` Hridya Valsaraju
2021-07-29  7:24 ` [PATCH 1/3] dma-buf: nuke seqno-fence Daniel Vetter
2021-07-29  7:24   ` Daniel Vetter

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