linux-kernel - Re: [PATCH v3 1/2] epoll: add nsec timeout support with epoll

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Message-ID: <CAK8P3a1cJf7+b5HCmFiLq+FdM+D+37rHYaftRgRYbhTyjwR6wg@mail.gmail.com>
Date:   Fri, 20 Nov 2020 20:23:27 +0100
From:   Arnd Bergmann <arnd@...nel.org>
To:     Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc:     Matthew Wilcox <willy@...radead.org>,
        David Laight <David.Laight@...lab.com>,
        Linux FS-devel Mailing List <linux-fsdevel@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Soheil Hassas Yeganeh <soheil.kdev@...il.com>,
        Arnd Bergmann <arnd@...db.de>, Shuo Chen <shuochen@...gle.com>,
        linux-man <linux-man@...r.kernel.org>,
        Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH v3 1/2] epoll: add nsec timeout support with epoll_pwait2

On Fri, Nov 20, 2020 at 5:01 PM Willem de Bruijn
<willemdebruijn.kernel@...il.com> wrote:
>
> On Fri, Nov 20, 2020 at 3:13 AM Arnd Bergmann <arnd@...nel.org> wrote:
> >
> > On Thu, Nov 19, 2020 at 9:13 PM Willem de Bruijn
> > <willemdebruijn.kernel@...il.com> wrote:
> > > On Thu, Nov 19, 2020 at 10:45 AM Arnd Bergmann <arnd@...nel.org> wrote:

> Thanks for the suggestion.
>
> I do have an initial patchset. As expected, it does involve quite a
> bit of code churn to pass slack through the callers. I'll take a look
> at your suggestion to simplify it.
>
> As is, the patchset is not ready to send to the list for possible
> merge. In the meantime, I did push the patchset to github at
> https://github.com/wdebruij/linux/commits/epoll-nstimeo-1 . I can send
> a version marked RFC to the list if that's easier.

Looks all good to me, just two small things I noticed that you can
address before sending the new series:

* The div_u64_rem() in ep_timeout_to_timespec() looks wrong, as
  you are actually dividing a 'long' that does not need it.

* In "epoll: wire up syscall epoll_pwait2", the alpha syscall has the
wrong number, it
   should be 110 higher than the others, not 109.

> Btw, the other change, to convert epoll implementation to timespec64
> before adding the syscall, equally adds some code churn compared to
> patch v3. But perhaps the end state is cleaner and more consistent.

Right, that's what I meant. If it causes too much churn, don't worry
about it it.

       Arndd