linux-kernel - Re: [RFC PATCH 0/8] vhost_tasks: Use CLONE

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Message-ID: <ea040d59-8760-32d3-ce5b-4120ed0efaa5@leemhuis.info>
Date:   Thu, 1 Jun 2023 13:29:19 +0200
From:   Thorsten Leemhuis <linux@...mhuis.info>
To:     Christian Brauner <brauner@...nel.org>,
        Mike Christie <michael.christie@...cle.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     oleg@...hat.com, nicolas.dichtel@...nd.com, axboe@...nel.dk,
        ebiederm@...ssion.com, linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, mst@...hat.com,
        sgarzare@...hat.com, jasowang@...hat.com, stefanha@...hat.com,
        Linux kernel regressions list <regressions@...ts.linux.dev>,
        hch@...radead.org, konrad.wilk@...cle.com
Subject: Re: [RFC PATCH 0/8] vhost_tasks: Use CLONE_THREAD/SIGHAND

On 01.06.23 12:47, Christian Brauner wrote:
> On Thu, Jun 01, 2023 at 09:58:38AM +0200, Thorsten Leemhuis wrote:
>> On 19.05.23 14:15, Christian Brauner wrote:
>>> On Thu, May 18, 2023 at 10:25:11AM +0200, Christian Brauner wrote:
>>>> On Wed, May 17, 2023 at 07:09:12PM -0500, Mike Christie wrote:
>>>>> This patch allows the vhost and vhost_task code to use CLONE_THREAD,
>>>>> CLONE_SIGHAND and CLONE_FILES. It's a RFC because I didn't do all the
>>>>> normal testing, haven't coverted vsock and vdpa, and I know you guys
>>>>> will not like the first patch. However, I think it better shows what
>>>>
>>>> Just to summarize the core idea behind my proposal is that no signal
>>>> handling changes are needed unless there's a bug in the current way
>>>> io_uring workers already work. All that should be needed is
>>>> s/PF_IO_WORKER/PF_USER_WORKER/ in signal.c.
>> [...]
>>>> So it feels like this should be achievable by adding a callback to
>>>> struct vhost_worker that get's called when vhost_worker() gets SIGKILL
>>>> and that all the users of vhost workers are forced to implement.
>>>>
>>>> Yes, it is more work but I think that's the right thing to do and not to
>>>> complicate our signal handling.
>>>>
>>>> Worst case if this can't be done fast enough we'll have to revert the
>>>> vhost parts. I think the user worker parts are mostly sane and are
>>>
>>> As mentioned, if we can't settle this cleanly before -rc4 we should
>>> revert the vhost parts unless Linus wants to have it earlier.
>>
>> Meanwhile -rc5 is just a few days away and there are still a lot of
>> discussions in the patch-set proposed to address the issues[1]. Which is
>> kinda great (albeit also why I haven't given it a spin yet), but on the
>> other hand makes we wonder:
> 
> You might've missed it in the thread but it seems everyone is currently
> operating under the assumption that the preferred way is to fix this is
> rather than revert. 

I saw that, but that was also a week ago already, so I slowly started to
wonder if plans might have/should be changed. Anyway: if that's still
the plan forward it's totally fine for me if it's fine for Linus. :-D

BTW: I for now didn't sit down to test Mike's patches, as due to all the
discussions I assumed new ones would be coming sooner or later anyway.
If it's worth giving them a shot, please let me know.

> [...]

Thx for the update!

Ciao, Thorsten