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 23:25, Andrew Marshall wrote:
> 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!

Correction: I cherry-picked and tested 8d09a88ef9d3cb7d21d45c39b7b7c31298d23998 (which was the change you identified), not 6b231248e97fc3. Apologies for any confusion.