[Intel-gfx] ✗ Fi.CI.IGT: failure for series starting with [v7,1/8] drm/i915/gem: Break out some shmem backend utils

[Tvrtko Ursulin]

On 07/10/2021 13:57, Christian König wrote:
> Am 07.10.21 um 12:51 schrieb Tvrtko Ursulin:
>>
>> On 07/10/2021 10:19, Christian König wrote:
>>> Am 07.10.21 um 11:15 schrieb Tvrtko Ursulin:
>>>> Hi,
>>>>
>>>> On 06/10/2021 16:26, Patchwork wrote:
>>>>> *Patch Details*
>>>>> *Series:*    series starting with [v7,1/8] drm/i915/gem: Break out 
>>>>> some shmem backend utils
>>>>> *URL:*    https://patchwork.freedesktop.org/series/95501/ 
>>>>> <https://patchwork.freedesktop.org/series/95501/>
>>>>> *State:*    failure
>>>>> *Details:* 
>>>>> https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_21264/index.html 
>>>>> <https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_21264/index.html>
>>>>>
>>>>>
>>>>>   CI Bug Log - changes from CI_DRM_10688_full -> Patchwork_21264_full
>>>>>
>>>>>
>>>>>     Summary
>>>>>
>>>>> *FAILURE*
>>>>>
>>>>> Serious unknown changes coming with Patchwork_21264_full absolutely 
>>>>> need to be
>>>>> verified manually.
>>>>>
>>>>> If you think the reported changes have nothing to do with the changes
>>>>> introduced in Patchwork_21264_full, please notify your bug team to 
>>>>> allow them
>>>>> to document this new failure mode, which will reduce false 
>>>>> positives in CI.
>>>>>
>>>>>
>>>>>     Possible new issues
>>>>>
>>>>> Here are the unknown changes that may have been introduced in 
>>>>> Patchwork_21264_full:
>>>>>
>>>>>
>>>>>       IGT changes
>>>>>
>>>>>
>>>>>         Possible regressions
>>>>>
>>>>>   *
>>>>>
>>>>>     igt at gem_sync@basic-many-each:
>>>>>
>>>>>       o shard-apl: NOTRUN -> INCOMPLETE
>>>>> <https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_21264/shard-apl7/igt@gem_sync@basic-many-each.html> 
>>>>>
>>>> Something still fishy in the unlocked iterator? Or 
>>>> dma_resv_get_fences using it?
>>>
>>> Probably the later. I'm going to take a look.
>>>
>>> Thanks for the notice,
>>> Christian.
>>>
>>>>
>>>> <6> [187.551235] [IGT] gem_sync: starting subtest basic-many-each
>>>> <1> [188.935462] BUG: kernel NULL pointer dereference, address: 
>>>> 0000000000000010
>>>> <1> [188.935485] #PF: supervisor write access in kernel mode
>>>> <1> [188.935495] #PF: error_code(0x0002) - not-present page
>>>> <6> [188.935504] PGD 0 P4D 0
>>>> <4> [188.935512] Oops: 0002 [#1] PREEMPT SMP NOPTI
>>>> <4> [188.935521] CPU: 2 PID: 1467 Comm: gem_sync Not tainted 
>>>> 5.15.0-rc4-CI-Patchwork_21264+ #1
>>>> <4> [188.935535] Hardware name:  /NUC6CAYB, BIOS 
>>>> AYAPLCEL.86A.0049.2018.0508.1356 05/08/2018
>>>> <4> [188.935546] RIP: 0010:dma_resv_get_fences+0x116/0x2d0
>>>> <4> [188.935560] Code: 10 85 c0 7f c9 be 03 00 00 00 e8 15 8b df ff 
>>>> eb bd e8 8e c6 ff ff eb b6 41 8b 04 24 49 8b 55 00 48 89 e7 8d 48 01 
>>>> 41 89 0c 24 <4c> 89 34 c2 e8 41 f2 ff ff 49 89 c6 48 85 c0 75 8c 48 
>>>> 8b 44 24 10
>>>> <4> [188.935583] RSP: 0018:ffffc900011dbcc8 EFLAGS: 00010202
>>>> <4> [188.935593] RAX: 0000000000000000 RBX: 00000000ffffffff RCX: 
>>>> 0000000000000001
>>>> <4> [188.935603] RDX: 0000000000000010 RSI: ffffffff822e343c RDI: 
>>>> ffffc900011dbcc8
>>>> <4> [188.935613] RBP: ffffc900011dbd48 R08: ffff88812d255bb8 R09: 
>>>> 00000000fffffffe
>>>> <4> [188.935623] R10: 0000000000000001 R11: 0000000000000000 R12: 
>>>> ffffc900011dbd44
>>>> <4> [188.935633] R13: ffffc900011dbd50 R14: ffff888113d29cc0 R15: 
>>>> 0000000000000000
>>>> <4> [188.935643] FS:  00007f68d17e9700(0000) 
>>>> GS:ffff888277900000(0000) knlGS:0000000000000000
>>>> <4> [188.935655] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>> <4> [188.935665] CR2: 0000000000000010 CR3: 000000012d0a4000 CR4: 
>>>> 00000000003506e0
>>>> <4> [188.935676] Call Trace:
>>>> <4> [188.935685]  i915_gem_object_wait+0x1ff/0x410 [i915]
>>>> <4> [188.935988]  i915_gem_wait_ioctl+0xf2/0x2a0 [i915]
>>>> <4> [188.936272]  ? i915_gem_object_wait+0x410/0x410 [i915]
>>>> <4> [188.936533]  drm_ioctl_kernel+0xae/0x140
>>>> <4> [188.936546]  drm_ioctl+0x201/0x3d0
>>>> <4> [188.936555]  ? i915_gem_object_wait+0x410/0x410 [i915]
>>>> <4> [188.936820]  ? __fget_files+0xc2/0x1c0
>>>> <4> [188.936830]  ? __fget_files+0xda/0x1c0
>>>> <4> [188.936839]  __x64_sys_ioctl+0x6d/0xa0
>>>> <4> [188.936848]  do_syscall_64+0x3a/0xb0
>>>> <4> [188.936859] entry_SYSCALL_64_after_hwframe+0x44/0xae
>>
>> FWIW if you disassemble the code it seems to be crashing in:
>>
>>   (*shared)[(*shared_count)++] = fence; // mov %r14, (%rdx, %rax, 8)
>>
>> RDX is *shared, RAX is *shared_count, RCX is *shared_count++ (for the 
>> next iteration. R13 is share and R12 shared_count.
>>
>> That *shared can contain 0000000000000010 makes no sense to me. At 
>> least yet. :)
> 
> Yeah, me neither. I've gone over the whole code multiple time now and 
> absolutely don't get what's happening here.
> 
> Adding some more selftests didn't helped either. As far as I can see the 
> code works as intended.
> 
> Do we have any other reports of crashes?

Yes, sporadic but present across different platforms since the change 
went it: 
https://intel-gfx-ci.01.org/tree/drm-tip/igt@gem_sync@basic-many-each.html. 
So issue is probably real.

Did not find any other tests failing with the same signature. Lakshmi 
are you perhaps able to search for the same or similar signature across 
the whole set of recent results?

Regards,

Tvrtko