[PATCH 1/2] dma-buf: add dma_fence_unwrap

[Christian König]

Am 28.03.22 um 16:22 schrieb Daniel Vetter:
> On Mon, Mar 28, 2022 at 12:28:31PM +0200, Christian König wrote:
>> Hi Ville & Daniel,
>>
>> Am 25.03.22 um 16:28 schrieb Christian König:
>>> Am 25.03.22 um 16:25 schrieb Ville Syrjälä:
>>>> On Fri, Mar 11, 2022 at 12:02:43PM +0100, Christian König wrote:
>>>>> Add a general purpose helper to deep dive into
>>>>> dma_fence_chain/dma_fence_array
>>>>> structures and iterate over all the fences in them.
>>>>>
>>>>> This is useful when we need to flatten out all fences in those
>>>>> structures.
>>>>>
>>>>> Signed-off-by: Christian König <christian.koenig at amd.com>
>>>> One of the dma-buf patches took down Intel CI. Looks like every
>>>> machine oopses in some sync_file thing now:
>>>> <1>[  260.470008] BUG: kernel NULL pointer dereference, address:
>>>> 0000000000000010
>>>> <1>[  260.470020] #PF: supervisor read access in kernel mode
>>>> <1>[  260.470025] #PF: error_code(0x0000) - not-present page
>>>> <6>[  260.470030] PGD 0 P4D 0
>>>> <4>[  260.470035] Oops: 0000 [#1] PREEMPT SMP NOPTI
>>>> <4>[  260.470040] CPU: 0 PID: 5306 Comm: core_hotunplug Not tainted
>>>> 5.17.0-CI-CI_DRM_11405+ #1
>>>> <4>[  260.470049] Hardware name: Intel Corporation Jasper Lake
>>>> Client Platform/Jasperlake DDR4 SODIMM RVP, BIOS
>>>> JSLSFWI1.R00.2385.D02.2010160831 10/16/2020
>>>> <4>[  260.470058] RIP: 0010:dma_fence_array_first+0x19/0x20
>> I've looked into this and the root cause seems to be that the new code
>> doesn't handle dma_fence_arrays with zero elements.
>>
>> That is rather easy to fix, but a dma_fence_array with zero number of
>> elements is most likely a bug because under the wrong circumstances it can
>> create a dma_fence instance which will never signal.
>>
>> I've send out a patch on Frinday ([PATCH] dma-buf: WIP dma_fence_array_first
>> fix) which avoids the crash and prints a warning if anybody tries to create
>> a dma_fence_array with zero length.
>>
>> Can you test this?
> It's in drm-tip now (in the fixup branch) so drm-tip results should have
> the result soonish:
>
> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fintel-gfx-ci.01.org%2Ftree%2Fdrm-tip%2Findex.html&data=04%7C01%7Cchristian.koenig%40amd.com%7C0afc74b5df0c4ea384af08da10c672fa%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637840742273792356%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=SL2CuMgM6lCSOhDTvs%2FaFg6zRlc7F3X%2BNkf6GuGMGXI%3D&reserved=0?

How do I find something in there? Is there a search function over all 
the test results?

Thanks,
Christian.

>
> Cheers, Daniel