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Date:   Wed, 29 Nov 2017 22:12:23 +0100
From:   Arnd Bergmann <>
To:     Deepa Dinamani <>
Cc:     Thomas Gleixner <>,
        John Stultz <>,
        Linux Kernel Mailing List <>,
        y2038 Mailman List <>,
        Arnaldo Carvalho de Melo <>,
        Benjamin Herrenschmidt <>,
        Christian Borntraeger <>,
        Catalin Marinas <>,
        Chris Metcalf <>,,
        David Miller <>,
        Helge Deller <>,,, gregkh <>,
        Heiko Carstens <>,
        Jan Hoeppner <>,
        "H. Peter Anvin" <>,
        "James E.J. Bottomley" <>,
        Julian Wiedmann <>,
        Linux API <>,
        linux-arch <>,
        "open list:RALINK MIPS ARCHITECTURE" <>,
        Parisc List <>,
        linuxppc-dev <>,
        linux-s390 <>,
        Mark Rutland <>,
        Ingo Molnar <>,
        Michael Ellerman <>,,,
        Paul Mackerras <>,
        Peter Zijlstra <>,
        Ralf Baechle <>,
        Steven Rostedt <>,
        Robert Richter <>,
        Martin Schwidefsky <>,, sparclinux <>,
        Stefan Haberland <>,
        Ursula Braun <>,
        Will Deacon <>,
        "the arch/x86 maintainers" <>
Subject: Re: [PATCH v2 00/10] posix_clocks: Prepare syscalls for 64 bit time_t conversion

On Wed, Nov 29, 2017 at 12:17 AM, Deepa Dinamani <> wrote:
> On Tue, Nov 28, 2017 at 6:17 AM, Arnd Bergmann <> wrote:
>> On Mon, Nov 27, 2017 at 11:29 PM, Deepa Dinamani <> wrote:
> Right. There are three options:
> 1. Use two configs to identify which syscalls need not be supported by
> new architectures.
> In this case it makes sense to say LEGACY_TIME_SYSCALLS and
> COMPAT_32BIT_TIME both need to be disabled for new architectures. And,
> I can reword the config to what you mention below.
> 2. Make the LEGACY_TIME_SYSCALLS eliminate non y2038 safe syscalls
> mentioned below only.
> In this case only the native and compat functions of the below
> mentioned syscalls need to be identified by the config. I like this
> option as this clearly identifies which syscalls are deprecated and do
> not have a 64 bit counterpart. Not all architectures need to support
> turning this off.
> 3. If we don't need either 1 or 2, then we could stick with what we
> have today in the series as CONFIG_64BIT_TIME will be deleted and they
> only need #ifdef CONFIG_64BIT.
> Let me know if anyone prefers something else.

I think I prefer to have both LEGACY_TIME_SYSCALLS to guard
the native deprecated syscalls (disabled on 32-bit architectures after
the conversion, and enabled on 64-bit architectures until
we merge the next one), and COMPAT_32BIT_TIME to guard the
compat versions of both the deprecated and the non-deprecated
syscalls (enabled on all existing 32-bit architectures after the
conversion, and on 64-bit architectures if they provide a compat
mode for the former).

Those two are not symmetric, but I think those are the most
common combinations, and the Kconfig symbol helps document
what they are.

There is one more category for things like io_getevents() and
rt_sigtimedwait that also need two separate compat versions,
one for 32-bit time_t and one for 64-bit time_t, but it seems better
to deal with those case-by-case rather than introducing another
Kconfig symbol.


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