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SubjectRe: [PATCH v3 1/3] timekeeping: Add a fast and NMI safe boot clock
On Fri, Jan 6, 2017 at 6:39 PM, Joel Fernandes <joelaf@google.com> wrote:
> Hi John,
>
> On Fri, Jan 6, 2017 at 4:48 PM, John Stultz <john.stultz@linaro.org> wrote:
>> On Thu, Nov 24, 2016 at 12:20 PM, Joel Fernandes <joelaf@google.com> wrote:
>>> This boot clock can be used as a tracing clock and will account for
>>> suspend time.
>>>
>>> To keep it NMI safe since we're accessing from tracing, we're not using a
>>> separate timekeeper with updates to monotonic clock and boot offset
>>> protected with seqlocks. This has the following minor side effects:
>>>
>>> (1) Its possible that a timestamp be taken after the boot offset is updated
>>> but before the timekeeper is updated. If this happens, the new boot offset
>>> is added to the old timekeeping making the clock appear to update slightly
>>> earlier:
>>> CPU 0 CPU 1
>>> timekeeping_inject_sleeptime64()
>>> __timekeeping_inject_sleeptime(tk, delta);
>>> timestamp();
>>> timekeeping_update(tk, TK_CLEAR_NTP...);
>>>
>>> (2) On 32-bit systems, the 64-bit boot offset (tk->offs_boot) may be
>>> partially updated. Since the tk->offs_boot update is a rare event, this
>>> should be a rare occurrence which postprocessing should be able to handle.
>>>
>>> Cc: Steven Rostedt <rostedt@goodmis.org>
>>> Cc: Thomas Gleixner <tglx@linutronix.de>
>>> Cc: John Stultz <john.stultz@linaro.org>
>>> Cc: Ingo Molnar <mingo@redhat.com>
>>> Signed-off-by: Joel Fernandes <joelaf@google.com>
>>
>> Hey Joel,
>> Hope you had a good new years! I was queuing this up for testing,
>
> Thanks, yes I had a great new years, hope you did too.
>
>> and the patch set no longer applies (to v4.10-rc2). Can you respin it
>> and resend it?
>
> Actually these patches are already in 4.10-rc2.

Ha! Well, apologies for missing that over the holidays.

Sorry for the noise.
-john

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