linux-kernel - Re: [PATCH] lib/vdso: use CLOCK_REALTIME

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Message-Id: <7147FC30-F9B4-4261-B2C1-08688A4E0D2B@android.com>
Date:   Thu, 11 Jun 2020 12:47:24 -0700
From:   Mark Salyzyn <salyzyn@...roid.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-kernel@...r.kernel.org, kernel-team@...roid.com,
        Chiawei Wang <chiaweiwang@...gle.com>, stable@...r.kernel.org,
        Andy Lutomirski <luto@...nel.org>,
        Vincenzo Frascino <vincenzo.frascino@....com>
Subject: Re: [PATCH] lib/vdso: use CLOCK_REALTIME_COARSE for time()

On Jun 11, 2020, at 12:34 PM, Thomas Gleixner <tglx@...utronix.de> wrote:
> 
> Mark Salyzyn <salyzyn@...roid.com> writes:
>> From: Chiawei Wang <chiaweiwang@...gle.com>
>> 
>> CLOCK_REALTIME in vdso data won't be updated if
>> __arch_use_vsyscall() returns false.
> 
> Errm!
> 
> # git grep __arch_use_vsyscall
> #
> 
> Aside of that update_vsyscall() updates CLOCK_REALTIME data
> unconditionally. No idea what this patch is solving.
> 
>> Cc: stable@...r.kernel.org # 5.4+
> 
> This # 5.4+ is pointless. You really want to add a fixes tag which pin
> points the commit which introduced the wreckage.
> 
> But thats moot as this is not fixing anything not even in 5.4.
> 
> 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.

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

Sorry for your troubles.

Sincerely — Mark Salyzyn