REGRESSION on linux-next (next-20251125)

REGRESSION on linux-next (next-20251125)

[Borah, Chaitanya Kumar]

Hello Christian,

Hope you are doing well. I am Chaitanya from the linux graphics team in 
Intel.

This mail is regarding a regression we are seeing in our CI runs[1] on
linux-next repository.

Since the version next-20251125 [2], we are seeing the following regression

`````````````````````````````````````````````````````````````````````````````````
(kms_busy:5818) sw_sync-CRITICAL: Test assertion failure function 
sw_sync_timeline_create_fence, file ../lib/sw_sync.c:117:
(kms_busy:5818) sw_sync-CRITICAL: Failed assertion: 
sw_sync_fd_is_valid(fence)
(kms_busy:5818) sw_sync-CRITICAL: Last errno: 2, No such file or directory
(kms_busy:5818) sw_sync-CRITICAL: Created invalid fence
(kms_busy:5818) igt_core-INFO: Stack trace:
(kms_busy:5818) igt_core-INFO:   #0 ../lib/igt_core.c:2075 
__igt_fail_assert()
(kms_busy:5818) igt_core-INFO:   #1 [sw_sync_timeline_create_fence+0x5f]
(kms_busy:5818) igt_core-INFO:   #2 ../tests/intel/kms_busy.c:122 
flip_to_fb()
(kms_busy:5818) igt_core-INFO:   #3 ../tests/intel/kms_busy.c:220 
test_flip()
(kms_busy:5818) igt_core-INFO:   #4 ../tests/intel/kms_busy.c:459 
__igt_unique____real_main411()
(kms_busy:5818) igt_core-INFO:   #5 ../tests/intel/kms_busy.c:411 main()
(kms_busy:5818) igt_core-INFO:   #6 [__libc_init_first+0x8a]
(kms_busy:5818) igt_core-INFO:   #7 [__libc_start_main+0x8b]
(kms_busy:5818) igt_core-INFO:   #8 [_start+0x25]
`````````````````````````````````````````````````````````````````````````````````
Details log can be found in [3].

After bisecting the tree, the following patch [4] seems to be the first 
"bad" commit

`````````````````````````````````````````````````````````````````````````````````````````````````````````
commit 8459303c886151b71e8de08b73e384fd2bb7499c
Author: Christian Brauner brauner@kernel.org
Date:   Sun Nov 23 17:33:55 2025 +0100

     dma: port sw_sync_ioctl_create_fence() to FD_PREPARE()
`````````````````````````````````````````````````````````````````````````````````````````````````````````

We also verified that if we revert the patch the issue is not seen.

Could you please check why the patch causes this regression and provide 
a fix if necessary?

Thank you.

Regards

Chaitanya

[1]
https://intel-gfx-ci.01.org/tree/linux-next/combined-alt.html?
[2] 
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?h=next-20251125
[3]
https://intel-gfx-ci.01.org/tree/linux-next/next-20251125/bat-arls-6/igt@kms_busy@basic.html
[4] 
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?h=next-20251125&id=8459303c886151b71e8de08b73e384fd2bb7499c

Re: REGRESSION on linux-next (next-20251125)

[Christian Brauner]

On Thu, Nov 27, 2025 at 11:35:32AM +0530, Borah, Chaitanya Kumar wrote:
> Hello Christian,
> 
> Hope you are doing well. I am Chaitanya from the linux graphics team in
> Intel.
> 
> This mail is regarding a regression we are seeing in our CI runs[1] on
> linux-next repository.
> 
> Since the version next-20251125 [2], we are seeing the following regression
> 
> `````````````````````````````````````````````````````````````````````````````````
> (kms_busy:5818) sw_sync-CRITICAL: Test assertion failure function
> sw_sync_timeline_create_fence, file ../lib/sw_sync.c:117:
> (kms_busy:5818) sw_sync-CRITICAL: Failed assertion:
> sw_sync_fd_is_valid(fence)
> (kms_busy:5818) sw_sync-CRITICAL: Last errno: 2, No such file or directory
> (kms_busy:5818) sw_sync-CRITICAL: Created invalid fence
> (kms_busy:5818) igt_core-INFO: Stack trace:
> (kms_busy:5818) igt_core-INFO:   #0 ../lib/igt_core.c:2075
> __igt_fail_assert()
> (kms_busy:5818) igt_core-INFO:   #1 [sw_sync_timeline_create_fence+0x5f]
> (kms_busy:5818) igt_core-INFO:   #2 ../tests/intel/kms_busy.c:122
> flip_to_fb()
> (kms_busy:5818) igt_core-INFO:   #3 ../tests/intel/kms_busy.c:220
> test_flip()
> (kms_busy:5818) igt_core-INFO:   #4 ../tests/intel/kms_busy.c:459
> __igt_unique____real_main411()
> (kms_busy:5818) igt_core-INFO:   #5 ../tests/intel/kms_busy.c:411 main()
> (kms_busy:5818) igt_core-INFO:   #6 [__libc_init_first+0x8a]
> (kms_busy:5818) igt_core-INFO:   #7 [__libc_start_main+0x8b]
> (kms_busy:5818) igt_core-INFO:   #8 [_start+0x25]
> `````````````````````````````````````````````````````````````````````````````````
> Details log can be found in [3].
> 
> After bisecting the tree, the following patch [4] seems to be the first
> "bad" commit
> 
> `````````````````````````````````````````````````````````````````````````````````````````````````````````
> commit 8459303c886151b71e8de08b73e384fd2bb7499c
> Author: Christian Brauner brauner@kernel.org
> Date:   Sun Nov 23 17:33:55 2025 +0100
> 
>     dma: port sw_sync_ioctl_create_fence() to FD_PREPARE()
> `````````````````````````````````````````````````````````````````````````````````````````````````````````
> 
> We also verified that if we revert the patch the issue is not seen.
> 
> Could you please check why the patch causes this regression and provide a
> fix if necessary?

Gah, sorry about this:

diff --git a/drivers/dma-buf/sync_file.c b/drivers/dma-buf/sync_file.c
index dc2e79a1b196..8d827b03e84c 100644
--- a/drivers/dma-buf/sync_file.c
+++ b/drivers/dma-buf/sync_file.c
@@ -244,7 +244,8 @@ static long sync_file_ioctl_merge(struct sync_file *sync_file,
        if (copy_to_user((void __user *)arg, &data, sizeof(data)))
                return -EFAULT;

-       return fd_publish(fdf);
+       fd_publish(fdf);
+       return 0;
 }

 static int sync_fill_fence_info(struct dma_fence *fence,

Pushing out the fix now. Can I trigger a new test myself somehow?

Re: REGRESSION on linux-next (next-20251125)

[Borah, Chaitanya Kumar]

On 11/27/2025 2:57 PM, Christian Brauner wrote:
> Pushing out the fix now. Can I trigger a new test myself somehow?

Thank you Christian!
Not really. Once it makes it to linux-next, our CI will pick it up. Till 
then let us validate locally.

Regards

Chaitanya

Re: REGRESSION on linux-next (next-20251125)

[Christian Brauner]

On Thu, Nov 27, 2025 at 03:03:27PM +0530, Borah, Chaitanya Kumar wrote:
> 
> 
> On 11/27/2025 2:57 PM, Christian Brauner wrote:
> > Pushing out the fix now. Can I trigger a new test myself somehow?
> 
> Thank you Christian!
> Not really. Once it makes it to linux-next, our CI will pick it up. Till
> then let us validate locally.

I just pushed:

https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git vfs-6.19.fd_prepare

If you want to test that, please.

Re: REGRESSION on linux-next (next-20251125)

[Borah, Chaitanya Kumar]

On 11/27/2025 4:13 PM, Christian Brauner wrote:
> I just pushed:
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git vfs-6.19.fd_prepare
> 
> If you want to test that, please.

aah! only the sync_file.c change you suggested was not fixing the issue. 
But with [1] on top of linux-next, the issue is now resolved.

It also solves another issue[2] we bisected (before I could report it to 
you, which is never a bad thing)

Thank you.

[1] 
https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git/commit/?h=vfs-6.19.fd_prepare&id=bf44cb6382f90fbda2eeae67065dc9401a967485
[2] 
https://intel-gfx-ci.01.org/tree/linux-next/next-20251125/bat-mtlp-8/igt@core_hotunplug@unbind-rebind.html

==
Chaitanya

Re: REGRESSION on linux-next (next-20251125)

[Christian Brauner]

On Thu, Nov 27, 2025 at 06:16:05PM +0530, Borah, Chaitanya Kumar wrote:
> 
> 
> On 11/27/2025 4:13 PM, Christian Brauner wrote:
> > I just pushed:
> > 
> > https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git vfs-6.19.fd_prepare
> > 
> > If you want to test that, please.
> 
> aah! only the sync_file.c change you suggested was not fixing the issue. But
> with [1] on top of linux-next, the issue is now resolved.
> 
> It also solves another issue[2] we bisected (before I could report it to
> you, which is never a bad thing)
> 
> Thank you.

Yes, sorry, two pretty obvious mistakes on my side. Thanks for testing!

> [1] https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git/commit/?h=vfs-6.19.fd_prepare&id=bf44cb6382f90fbda2eeae67065dc9401a967485
> [2] https://intel-gfx-ci.01.org/tree/linux-next/next-20251125/bat-mtlp-8/igt@core_hotunplug@unbind-rebind.html