linux-kernel - Re: Are CAP_SYS_ADMIN and CAP_SYS

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Message-ID: <20210325140928.fuu2iap54ysevssz@steredhat>
Date:   Thu, 25 Mar 2021 15:09:28 +0100
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Jens Axboe <axboe@...nel.dk>,
        Pavel Begunkov <asml.silence@...il.com>
Cc:     io-uring@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Are CAP_SYS_ADMIN and CAP_SYS_NICE still needed for SQPOLL?

On Thu, Mar 25, 2021 at 08:02:45AM -0600, Jens Axboe wrote:
>On 3/25/21 7:44 AM, Pavel Begunkov wrote:
>> On 25/03/2021 11:33, Stefano Garzarella wrote:
>>> Hi Jens, Hi Pavel,
>>> I was taking a look at the new SQPOLL handling with io_thread instead of kthread. Great job! Really nice feature that maybe can be reused also in other scenarios (e.g. vhost).
>>>
>>> Regarding SQPOLL, IIUC these new threads are much closer to user threads, so is there still a need to require CAP_SYS_ADMIN and CAP_SYS_NICE to enable SQPOLL?
>>
>> Hmm, good question. If there are under same cgroup (should be in
>> theory), and if we add more scheduling points (i.e. need_resched()), and
>> don't see a reason why not. Jens?
>>
>> Better not right away though. IMHO it's safer to let the change settle
>> down for some time.
>
>Yes, agree on both counts - we are not going to need elevated privileges
>going forward, but I'd also rather defer making that change until 5.13
>so we have a bit more time on the current (new) base first.

Yeah, that makes sense to me!

Thank you both for the quick clarification,
Stefano