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

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Message-ID: <ab8c9f95-c9e9-de04-4e28-78163a32da80@leemhuis.info>
Date:   Thu, 1 Jun 2023 09:58:38 +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 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:

Is it maybe time to revert the vhost parts for 6.4 and try again next cycle?

[1]
https://lore.kernel.org/all/20230522025124.5863-1-michael.christie@oracle.com/

Ciao, Thorsten "not sure if I'm asking because I'm affected, or because
it's my duty as regression tracker" Leemhuis