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Date:   Tue, 20 Aug 2019 20:47:55 +0200
From:   Alexandre Belloni <alexandre.belloni@bootlin.com>
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     Karel Zak <kzak@redhat.com>,
        Lennart Poettering <mzxreary@0pointer.de>,
        Arnd Bergmann <arnd@arndb.de>,
        "Theodore Y. Ts'o" <tytso@mit.edu>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        John Stultz <john.stultz@linaro.org>,
        Stephen Boyd <sboyd@kernel.org>,
        Florian Weimer <fweimer@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Alistair Francis <alistair.francis@wdc.com>,
        GNU C Library <libc-alpha@sourceware.org>,
        OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Subject: Re: New kernel interface for sys_tz and timewarp?
Message-ID: <20190820184755.GP3545@piout.net>
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On 19/08/2019 15:43:03+0200, Thomas Gleixner wrote:
> On Mon, 19 Aug 2019, Karel Zak wrote:
> > On Wed, Aug 14, 2019 at 11:32:08AM +0200, Alexandre Belloni wrote:
> > > On 14/08/2019 11:09:36+0200, Lennart Poettering wrote:
> > > > On Mi, 14.08.19 10:31, Arnd Bergmann (arnd@arndb.de) wrote:
> > > > 
> > > > > - glibc stops passing the caller timezone argument to the kernel
> > > > > - the distro kernel disables CONFIG_RTC_HCTOSYS,
> > > > >   CONFIG_RTC_SYSTOHC  and CONFIG_GENERIC_CMOS_UPDATE
> > > > 
> > > > What's the benefit of letting userspace do this? It sounds a lot more
> > > > fragile to leave this syncing to userspace if the kernel can do this
> > > > trivially on its own.
> > 
> > Good point, why CONFIG_RTC_SYSTOHC has been added to the kernel? 
> 
> 023f333a99ce ("NTP: Add a CONFIG_RTC_SYSTOHC configuration")

This answers only half the question. The follow up is then why do we
need update_persistent_clock?

-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com