linux-kernel - Re: [PATCH v2] clocksource: Defer override invalidation unless clock is unstable

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Message-ID: <CALAqxLV6v6rcarW30Aoqpxk-wtgUa=wsn-5DEz4__CEJX4FBPA@mail.gmail.com>
Date:	Wed, 17 Aug 2016 13:12:00 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	Kyle Walker <kwalker@...hat.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] clocksource: Defer override invalidation unless clock
 is unstable

On Sat, Aug 6, 2016 at 9:07 AM, Kyle Walker <kwalker@...hat.com> wrote:
> Clocksources don't get the VALID_FOR_HRES flag until they have been
> checked by a watchdog. However, when using an override, the
> clocksource_select logic will clear the override value if the
> clocksource is not marked VALID_FOR_HRES during that inititial check.
> When using the boot arguments clocksource=<foo>, this selection can
> run before the watchdog, and can cause the override to be incorrectly
> cleared.
>
> To address this condition, the override_name is only invalidated for
> unstable clocksources. Otherwise, the override is left intact until after
> the watchdog has validated the clocksource as stable/unstable.
>
> Signed-off-by: Kyle Walker <kwalker@...hat.com>

Queued for testing and targeting 4.9

thanks
-john