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Subject: Re: [PATCH] lib/vdso: use CLOCK_REALTIME_COARSE for time()
From:   Mark Salyzyn <salyzyn@android.com>
In-Reply-To: <878sgt1jo2.fsf@nanos.tec.linutronix.de>
Date:   Thu, 11 Jun 2020 12:47:24 -0700
Cc:     linux-kernel@vger.kernel.org, kernel-team@android.com,
        Chiawei Wang <chiaweiwang@google.com>, stable@vger.kernel.org,
        Andy Lutomirski <luto@kernel.org>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>
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Message-Id: <7147FC30-F9B4-4261-B2C1-08688A4E0D2B@android.com>
References: <20200611155804.65204-1-salyzyn@android.com>
 <878sgt1jo2.fsf@nanos.tec.linutronix.de>
To:     Thomas Gleixner <tglx@linutronix.de>
Sender: linux-kernel-owner@vger.kernel.org
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On Jun 11, 2020, at 12:34 PM, Thomas Gleixner <tglx@linutronix.de> =
wrote:
>=20
> Mark Salyzyn <salyzyn@android.com> writes:
>> From: Chiawei Wang <chiaweiwang@google.com>
>>=20
>> CLOCK_REALTIME in vdso data won't be updated if
>> __arch_use_vsyscall() returns false.
>=20
> Errm!
>=20
> # git grep __arch_use_vsyscall
> #
>=20
> Aside of that update_vsyscall() updates CLOCK_REALTIME data
> unconditionally. No idea what this patch is solving.
>=20
>> Cc: stable@vger.kernel.org # 5.4+
>=20
> This # 5.4+ is pointless. You really want to add a fixes tag which pin
> points the commit which introduced the wreckage.
>=20
> But thats moot as this is not fixing anything not even in 5.4.
>=20
> I assume this was developed against some Frankenkernel which has a =
messy
> backport or a snapshot of some development version of that vdso stuff.

Yes, problem code was removed with =
52338415cf4d4064ae6b8dd972dadbda841da4fa not applied.

4.19 back port without time namespaces, chip vendor using =
__arch_use_vsyscall to solve a chip errata.

>=20
> Not that I want to know, but please make sure that something you send =
my
> way makes sense on sane kernels.
>=20
> Oh well.
>=20
> Thanks,
>=20
>        tglx

Sorry for your troubles.

Sincerely =E2=80=94 Mark Salyzyn