Re: Stable backport (was "Re: PROBLEM: io_uring hang causing uninterruptible sleep state on 6.6.59")

["Andrew Marshall" <andrew@johnandrewmarshall.com>]

On Sun, Nov 3, 2024, at 21:38, Jens Axboe wrote:
> On 11/3/24 5:06 PM, Jens Axboe wrote:
>> On 11/3/24 5:01 PM, Keith Busch wrote:
>>> On Sun, Nov 03, 2024 at 04:53:27PM -0700, Jens Axboe wrote:
>>>> On 11/3/24 4:47 PM, Andrew Marshall wrote:
>>>>> I identified f4ce3b5d26ce149e77e6b8e8f2058aa80e5b034e as the likely
>>>>> problematic commit simply by browsing git log. As indicated above;
>>>>> reverting that atop 6.6.59 results in success. Since it is passing on
>>>>> 6.11.6, I suspect there is some missing backport to 6.6.x, or some
>>>>> other semantic merge conflict. Unfortunately I do not have a compact,
>>>>> minimal reproducer, but can provide my large one (it is testing a
>>>>> larger build process in a VM) if needed?there are some additional
>>>>> details in the above-linked downstream bug report, though. I hope that
>>>>> having identified the problematic commit is enough for someone with
>>>>> more context to go off of. Happy to provide more information if
>>>>> needed.
>>>>
>>>> Don't worry about not having a reproducer, having the backport commit
>>>> pin pointed will do just fine. I'll take a look at this.
>>>
>>> I think stable is missing:
>>>
>>>   6b231248e97fc3 ("io_uring: consolidate overflow flushing")
>> 
>> I think you need to go back further than that, this one already
>> unconditionally holds ->uring_lock around overflow flushing...
>
> Took a look, it's this one:
>
> commit 8d09a88ef9d3cb7d21d45c39b7b7c31298d23998
> Author: Pavel Begunkov <asml.silence@gmail.com>
> Date:   Wed Apr 10 02:26:54 2024 +0100
>
>     io_uring: always lock __io_cqring_overflow_flush
>
> Greg/stable, can you pick this one for 6.6-stable? It picks
> cleanly.
>
> For 6.1, which is the other stable of that age that has the backport,
> the attached patch will do the trick.
>
> With that, I believe it should be sorted. Hopefully that can make
> 6.6.60 and 6.1.116.
>
> -- 
> Jens Axboe
> Attachments:
> * 0001-io_uring-always-lock-__io_cqring_overflow_flush.patch

Cherry-picking 6b231248e97fc3 onto 6.6.59, I can confirm it passes my reproducer (run a few times). Your first quick patch also passed, for what it’s worth. Thanks for the quick responses!