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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Sat, 1 Dec 2018 00:15:08 +0100
Message-ID: <CAK8P3a3XRLUsoG0GJ8mkp6LGHRHtVg0eV0RZfrMoPcEgyHcCZA@mail.gmail.com>
Subject: Re: [PATCH v2] signal: add procfd_signal() syscall
To:     Daniel Colascione <dancol@google.com>
Cc:     christian@brauner.io, Andy Lutomirski <luto@kernel.org>,
        "Eric W . Biederman" <ebiederm@xmission.com>,
        Florian Weimer <fweimer@redhat.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "Serge E. Hallyn" <serge@hallyn.com>, Jann Horn <jannh@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Oleg Nesterov <oleg@redhat.com>, cyphar@cyphar.com,
        Al Viro <viro@zeniv.linux.org.uk>,
        Linux FS-devel Mailing List <linux-fsdevel@vger.kernel.org>,
        Linux API <linux-api@vger.kernel.org>,
        Tim Murray <timmurray@google.com>, linux-man@vger.kernel.org,
        Kees Cook <keescook@chromium.org>
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On Sat, Dec 1, 2018 at 12:12 AM Arnd Bergmann <arnd@arndb.de> wrote:
>
> On Sat, Dec 1, 2018 at 12:05 AM Daniel Colascione <dancol@google.com> wrote:
> > On Fri, Nov 30, 2018 at 2:26 PM Christian Brauner <christian@brauner.io> wrote:
> > > On December 1, 2018 11:09:58 AM GMT+13:00, Arnd Bergmann <arnd@arndb.de> wrote:
> > >
> > > One humble point I would like to make is that what I care about most is a sensible way forward without having to redo essential parts of how syscalls work.
> > > I don't want to introduce a sane, small syscall that ends up breaking all over the place because we decided to fix past mistakes that technically have nothing to do with the patch itself.
> > > However, I do sympathize and understand these concerns.
> >
> > IMHO, it's fine to just replicate all the splits we have for the
> > existing signal system calls. It's ugly, but once it's done, it'll be
> > done for a long time. I can't see a need to add even more signal
> > system calls after this one.
>
> We definitely need waitid_time64() and rt_sigtimedwait_time64()
> in the very near future.

To clarify: we probably don't need rt_sigtimedwait_time64() for
x32, as it already has a 64-bit time_t. We might need waitid_time64()
or something similar though, since the plan now is to change the
time resolution for rusage to nanoseconds (__kernel_timespec)
now. The exact behavior and name of waitid_time64() is still
a matter of discussion.

       Arnd