From: Will Deacon <will.deacon@arm.com>
To: John Stultz <john.stultz@linaro.org>
Cc: lkml <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>,
Miroslav Lichvar <mlichvar@redhat.com>,
Richard Cochran <richardcochran@gmail.com>,
Prarit Bhargava <prarit@redhat.com>,
Stephen Boyd <stephen.boyd@linaro.org>,
Kevin Brodsky <kevin.brodsky@arm.com>,
Daniel Mentz <danielmentz@google.com>
Subject: Re: [RFC][PATCH 3/4] arm64: vdso: Fix nsec handling for CLOCK_MONOTONIC_RAW
Date: Tue, 30 May 2017 10:38:43 +0100 [thread overview]
Message-ID: <20170530093842.GA32289@arm.com> (raw)
In-Reply-To: <1495856035-6622-4-git-send-email-john.stultz@linaro.org>
On Fri, May 26, 2017 at 08:33:54PM -0700, John Stultz wrote:
> From: Will Deacon <will.deacon@arm.com>
>
> Commit 45a7905fc48f ("arm64: vdso: defer shifting of nanosecond
> component of timespec") fixed sub-ns inaccuracies in our vDSO
> clock_gettime implementation by deferring the right-shift of the
> nanoseconds components until after the timespec addition, which
> operates on left-shifted values. That worked nicely until
> support for CLOCK_MONOTONIC_RAW was added in 49eea433b326
> ("arm64: Add support for CLOCK_MONOTONIC_RAW in clock_gettime()
> vDSO"). Noticing that the core timekeeping code never set
> tkr_raw.xtime_nsec, the vDSO implementation didn't bother
> exposing it via the data page and instead took the unshifted
> tk->raw_time.tv_nsec value which was then immediately shifted
> left in the vDSO code.
>
> Now that the core code is actually setting tkr_raw.xtime_nsec,
> we need to take that into account in the vDSO by adding it to
> the shifted raw_time value. Rather than do that at each use (and
> expand the data page in the process), instead perform the
> shift/addition operation when populating the data page and
> remove the shift from the vDSO code entirely.
>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Miroslav Lichvar <mlichvar@redhat.com>
> Cc: Richard Cochran <richardcochran@gmail.com>
> Cc: Prarit Bhargava <prarit@redhat.com>
> Cc: Stephen Boyd <stephen.boyd@linaro.org>
> Cc: Kevin Brodsky <kevin.brodsky@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: Daniel Mentz <danielmentz@google.com>
> Reported-by: John Stultz <john.stultz@linaro.org>
> Acked-by: Acked-by: Kevin Brodsky <kevin.brodsky@arm.com>
I don't think Kevin liked it *that* much ^^
Will
next prev parent reply other threads:[~2017-05-30 9:38 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-27 3:33 [RFC][PATCH 0/4] Fixes for two recently found timekeeping bugs John Stultz
2017-05-27 3:33 ` [RFC][PATCH 1/4] time: Fix clock->read(clock) race around clocksource changes John Stultz
2017-05-27 7:31 ` Ingo Molnar
2017-05-27 3:33 ` [RFC][PATCH 2/4] time: Fix CLOCK_MONOTONIC_RAW sub-nanosecond accounting John Stultz
2017-05-27 7:36 ` Ingo Molnar
2017-05-30 18:42 ` Daniel Mentz
2017-05-27 3:33 ` [RFC][PATCH 3/4] arm64: vdso: Fix nsec handling for CLOCK_MONOTONIC_RAW John Stultz
2017-05-30 9:38 ` Will Deacon [this message]
2017-05-27 3:33 ` [RFC][PATCH 4/4] time: Clean up CLOCK_MONOTONIC_RAW time handling John Stultz
2017-08-25 13:40 ` Chris Wilson
2017-08-25 18:55 ` John Stultz
2017-08-25 21:16 ` John Stultz
2017-08-25 22:57 ` [RFC][PATCH] time: Fix ktime_get_raw() issues caused by incorrect base accumulation John Stultz
2017-08-26 10:20 ` Chris Wilson
2017-08-26 14:10 ` [tip:timers/urgent] time: Fix ktime_get_raw() " tip-bot for John Stultz
2017-05-27 7:38 ` [RFC][PATCH 0/4] Fixes for two recently found timekeeping bugs Ingo Molnar
2017-05-27 16:16 ` John Stultz
2017-05-28 8:54 ` Ingo Molnar
[not found] ` <CAE2F3rBuOJqLs5Cu7A9wEruZj1Vmnpy6qAYW=U9FVAOEP73pdg@mail.gmail.com>
2017-05-31 0:11 ` Daniel Mentz
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