Re: [PATCH v3] mm: Fix possible deadlock in console_trylock_spinning

[Gu Bowen <gubowen5@huawei.com>]

On 8/14/2025 9:08 PM, Catalin Marinas wrote:
> On Thu, Aug 14, 2025 at 10:33:56AM +0800, Gu Bowen wrote:
>> On 8/14/2025 6:56 AM, Andrew Morton wrote:
>>> I'm not sure which kernel version this was against, but kmemleak.c has
>>> changed quite a lot.
>>>
>>> Could we please see a patch against a latest kernel version?  Linus
>>> mainline will suit.
>>>
>>> Thanks.
>>
>> I discovered this issue in kernel version 5.10. Afterwards, I reviewed the
>> code of the mainline version and found that this deadlock path no longer
>> exists due to the refactoring of console_lock in v6.2-rc1. For details on
>> the refactoring, you can refer to this link :
>> https://lore.kernel.org/all/20221116162152.193147-1-john.ogness@linutronix.de/.
>> Therefore, theoretically, this issue existed before the refactoring of
>> console_lock.
> 
> Oh, so you can no longer hit this issue with mainline. This wasn't
> mentioned (or I missed it) in the commit log.
> 
> So this would be a stable-only fix that does not have a correspondent
> upstream. Adding Greg for his opinion.
> 

I have discovered that I made a mistake, this fix patch should be merged 
into the mainline. Since we have identified two types of deadlocks, the 
AA deadlock [1] and the ABBA deadlock[2], the latter's deadlock path no 
longer exists in the mainline due to the 40 patches that refactored 
console_lock. However, the AA deadlock issue persists, so I believe this 
fix should be applied to the mainline.

[1] 
https://lore.kernel.org/all/20250731-kmemleak_lock-v1-1-728fd470198f@debian.org/#t
[2] https://lore.kernel.org/all/20250730094914.566582-1-gubowen5@huawei.com/

Best Regards,
Guber