linux-kernel - Re: [PATCH 6/6] eventpoll: add support for min-wait

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Message-ID: <33832500-ddf3-dc2b-a765-046d46031991@kernel.dk>
Date:   Tue, 8 Nov 2022 15:29:16 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc:     Soheil Hassas Yeganeh <soheil@...gle.com>,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        Shakeel Butt <shakeelb@...gle.com>
Subject: Re: [PATCH 6/6] eventpoll: add support for min-wait

On 11/8/22 3:25 PM, Willem de Bruijn wrote:
>>> This would be similar to the approach that willemb@...gle.com used
>>> when introducing epoll_pwait2.
>>
>> I have, see other replies in this thread, notably the ones with Stefan
>> today. Happy to do that, and my current branch does split out the ctl
>> addition from the meat of the min_wait support for this reason. Can't
>> seem to find a great way to do it, as we'd need to move to a struct
>> argument for this as epoll_pwait2() is already at max arguments for a
>> syscall. Suggestions more than welcome.
> 
> Expect an array of two timespecs as fourth argument?

Unfortunately even epoll_pwait2() doesn't have any kind of flags
argument to be able to do tricks like that... But I guess we could do
that with epoll_pwait3(), but it'd be an extra indirection for the copy
at that point (copy array of pointers, copy pointer if not NULL), which
would be unfortunate. I'd hate to have to argue that API to anyone, let
alone Linus, when pushing the series.

-- 
Jens Axboe