linux-kernel - Re: Are CAP_SYS_ADMIN and CAP_SYS

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Date:   Thu, 25 Mar 2021 08:02:45 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Pavel Begunkov <asml.silence@...il.com>,
        Stefano Garzarella <sgarzare@...hat.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 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.

-- 
Jens Axboe