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From: Arnd Bergmann <arnd@arndb.de>
Date: Fri, 29 Nov 2019 16:17:45 +0100
Message-ID: <CAK8P3a1mrFgRyh5Fgv-d8Szd2pq0T6Ac7wL3ogeYcf-Uyrg4ZQ@mail.gmail.com>
Subject: Re: 64 bit time regression in recvmmsg()
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To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Anton Ivanov <anton.ivanov@cambridgegreys.com>, linux-um <linux-um@lists.infradead.org>
List-ID: <linux-um.lists.infradead.org>

On Fri, Nov 29, 2019 at 4:05 PM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> On Fri, Nov 29, 2019 at 3:34 PM Anton Ivanov
> <anton.ivanov@cambridgegreys.com> wrote:
> > Unfortunately, it looks like the recent year 2038 have broken
> > compatibility for one particular syscall interface we use - recvmmsg.
> >
> > The host now occasionally returns -22 (EINVAL) and the only way I see
> > for this to happen looking at the source is if when it gets something
> > bogus as a timeout.
> >
> > I think I have eliminated all other possible sources for this error.
> >
> > The picture can be observed when using a 64 bit host 5.2 kernel on a
> > Debian 64 bit buster userspace (glibc compiled vs 4.19 headers).
> >
> > The code as it is written at present retries and by sheer luck and
> > perseverance it manages to work, but this needs to be fixed.

I only see a single call to recvmmsg() in arch/um, in uml_vector_recvmmsg(),
and this passes a NULL timeout pointer, is this the one that broke or
should I be looking at something else?

Do I understand you right that the regression is on a pure 64-bit system?

     Arnd