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

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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@xxxxxxxxx
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@xxxxxxxxx/

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

--
Cheers,

David / dhildenb




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