Regression on linux-next (next-20240712)

Regression on linux-next (next-20240712)

[Borah, Chaitanya Kumar]

Hello Pei,

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.

In version next-20240712[2], we saw the following regression (currently being masked by another regression)

`````````````````````````````````````````````````````````````````````````````````
<4>[   14.530533] ============================================
<4>[   14.530533] WARNING: possible recursive locking detected
<4>[   14.530534] 6.10.0-rc7-next-20240712-next-20240712-g3fe121b62282+ #1 Not tainted
<4>[   14.530535] --------------------------------------------
<4>[   14.530535] (direxec)/171 is trying to acquire lock:
<4>[   14.530536] ffff8881010725d8 (&mm->mmap_lock){++++}-{3:3}, at: unmap_single_vma+0xea/0x170
<4>[   14.530541] 
                  but task is already holding lock:
<4>[   14.530542] ffff8881010725d8 (&mm->mmap_lock){++++}-{3:3}, at: exit_mmap+0x6a/0x450
<4>[   14.530545] 
                  other info that might help us debug this:
<4>[   14.530545]  Possible unsafe locking scenario:
`````````````````````````````````````````````````````````````````````````````````
Details log can be found in [3].

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

`````````````````````````````````````````````````````````````````````````````````````````````````````````
commit a13252049629a8225f38a9be7d8d4fc4ff5350e8
Author: Pei Li mailto:peili.dev@gmail.com
Date:   Wed Jul 10 22:13:17 2024 -0700

    mm: fix mmap_assert_locked() in follow_pte()

`````````````````````````````````````````````````````````````````````````````````````````````````````````

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-20240712 
[3] https://gfx-ci.igk.intel.com/tree/linux-next/next-20240712/bat-arlh-2/boot0.txt
[4] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?h=next-20240712&id=a13252049629a8225f38a9be7d8d4fc4ff5350e8

Re: Regression on linux-next (next-20240712)

[David Hildenbrand]

On 16.07.24 07:37, Borah, Chaitanya Kumar wrote:
> Hello Pei,
> 
> 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.
> 
> In version next-20240712[2], we saw the following regression (currently being masked by another regression)
> 
> `````````````````````````````````````````````````````````````````````````````````
> <4>[   14.530533] ============================================
> <4>[   14.530533] WARNING: possible recursive locking detected
> <4>[   14.530534] 6.10.0-rc7-next-20240712-next-20240712-g3fe121b62282+ #1 Not tainted
> <4>[   14.530535] --------------------------------------------
> <4>[   14.530535] (direxec)/171 is trying to acquire lock:
> <4>[   14.530536] ffff8881010725d8 (&mm->mmap_lock){++++}-{3:3}, at: unmap_single_vma+0xea/0x170
> <4>[   14.530541]
>                    but task is already holding lock:
> <4>[   14.530542] ffff8881010725d8 (&mm->mmap_lock){++++}-{3:3}, at: exit_mmap+0x6a/0x450
> <4>[   14.530545]
>                    other info that might help us debug this:
> <4>[   14.530545]  Possible unsafe locking scenario:
> `````````````````````````````````````````````````````````````````````````````````
> Details log can be found in [3].
> 
> After bisecting the tree, the following patch [4] seems to be the first "bad"
> commit
> 
> `````````````````````````````````````````````````````````````````````````````````````````````````````````
> commit a13252049629a8225f38a9be7d8d4fc4ff5350e8
> Author: Pei Li mailto:peili.dev@gmail.com
> Date:   Wed Jul 10 22:13:17 2024 -0700
> 
>      mm: fix mmap_assert_locked() in follow_pte()
> 
> `````````````````````````````````````````````````````````````````````````````````````````````````````````
> 
> 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?

This is know.

There is a discussion along the original patch [1] on how to do it 
differently. But likely we'll tackle it differently [2]. So this patch 
should be dropped for -- which I think already happened because I cannot 
spot that patch in mm-unstable anymore.

[1] https://lore.kernel.org/all/20240710-bug12-v1-1-0e5440f9b8d3@gmail.com/

[2] https://lkml.kernel.org/r/20240712144244.3090089-1-peterx@redhat.com

-- 
Cheers,

David / dhildenb

Re: Regression on linux-next (next-20240712)

[Andrew Morton]

On Wed, 17 Jul 2024 13:00:58 +0200 David Hildenbrand <david@redhat.com> wrote:

> > Could you please check why the patch causes this regression and provide a fix if necessary?
> 
> This is know.
> 
> There is a discussion along the original patch [1] on how to do it 
> differently. But likely we'll tackle it differently [2]. So this patch 
> should be dropped for -- which I think already happened because I cannot 
> spot that patch in mm-unstable anymore.

Yes, I dropped it on July 15.

RE: Regression on linux-next (next-20240712)

[Borah, Chaitanya Kumar]

> -----Original Message-----
> From: Andrew Morton <akpm@linux-foundation.org>
> Sent: Thursday, July 18, 2024 1:31 AM
> To: David Hildenbrand <david@redhat.com>
> Cc: Borah, Chaitanya Kumar <chaitanya.kumar.borah@intel.com>;
> peili.dev@gmail.com; Nikula, Jani <jani.nikula@intel.com>; Saarinen, Jani
> <jani.saarinen@intel.com>; Kurmi, Suresh Kumar
> <suresh.kumar.kurmi@intel.com>; intel-gfx@lists.freedesktop.org; linux-
> mm@kvack.org; linux-kernel@vger.kernel.org
> Subject: Re: Regression on linux-next (next-20240712)
> 
> On Wed, 17 Jul 2024 13:00:58 +0200 David Hildenbrand <david@redhat.com>
> wrote:
> 
> > > Could you please check why the patch causes this regression and provide
> a fix if necessary?
> >
> > This is know.
> >
> > There is a discussion along the original patch [1] on how to do it
> > differently. But likely we'll tackle it differently [2]. So this patch
> > should be dropped for -- which I think already happened because I
> > cannot spot that patch in mm-unstable anymore.
> 
> Yes, I dropped it on July 15.

Thank you. Our CI runs seems to have recovered from the regression.

Regards

Chaitanya