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SubjectRe: [syzbot] possible deadlock in loop_add
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On 16/7/21 7:00 am, Miquel Raynal wrote:
> Hello,
>
> Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com> wrote on Mon, 12 Jul
> 2021 16:29:16 +0800:
>
>> On 12/7/21 1:27 pm, Christoph Hellwig wrote:
>>> On Sat, Jul 10, 2021 at 09:16:38PM +0800, Hillf Danton wrote:
>>>> To break the lock chain, un/register blkdev without mtd_table_mutex held.
>>>
>>> Yes, Desmond Cheong Zhi Xi sent pretty much the same patch on June 18th
>>> (mtd: break circular locks in register_mtd_blktrans), but it did not get
>>> picked up.
>>>
>>
>> I believe Miquèl was waiting for -rc1 to apply it.
>
> Indeed, I already applied it but did not advertise yet.
>

Thanks Miquèl!

>>
>> But taking a closer look, although the fix for the register path is the same, Hillf Danton's proposed patch additionally avoids inverting the lock hierarchy on the unregister path. So I believe this new patch should be more robust.
>
> We can definitely do this in two steps if you want.
>

Sounds good, I'll prepare a patch with Hillf's suggestion for the
unregister path.

> Thanks,
> Miquèl
>

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