Re: [PATCH] clocksource_cyc2ns: avoid overflowing 64 bits

From	John Stultz <john.stultz@linaro.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH] clocksource_cyc2ns: avoid overflowing 64 bits
Date	2016-11-16 21:10 +0100
Message-ID	<sEeGR-7vu-1@gated-at.bofh.it> (permalink)
References	<sEbJ0-5pV-11@gated-at.bofh.it> <sEcOJ-6ob-9@gated-at.bofh.it> <sEedQ-76Q-11@gated-at.bofh.it> <sEenw-7aa-5@gated-at.bofh.it> <sEeGR-7vu-3@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Wed, Nov 16, 2016 at 11:56 AM, Chris Metcalf <cmetcalf@mellanox.com> wrote:
> On 11/16/2016 2:45 PM, John Stultz wrote:
>>
>> On Wed, Nov 16, 2016 at 11:30 AM, Chris Metcalf <cmetcalf@mellanox.com>
>> wrote:
>>>
>>> diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
>>> index 08398182f56e..5444429884b8 100644
>>> --- a/include/linux/clocksource.h
>>> +++ b/include/linux/clocksource.h
>>> @@ -171,6 +171,10 @@ static inline u32 clocksource_hz2mult(u32 hz, u32
>>> shift_constant)
>>>    *
>>>    * Converts cycles to nanoseconds, using the given mult and shift.
>>>    *
>>> + * The code is optimized for performance and not intended to work
>>> + * with absolute clocksource cycles, as it will easily overflow,
>>> + * but just intended for relative (delta) clocksource cycles.
>>> + *
>>>    * XXX - This could use some mult_lxl_ll() asm optimization
>>
>> Just as a heads up, it seems your working against an older kernel, as
>> this didn't apply. Its simple enough to fix up, so I'll do so, but in
>> the future, please submit patches against something close to Linus
>> HEAD.
>
>
> Oops, sorry; it wasn't version skew (I'm at v4.9-rc4) but whitespace damage.
> I assumed if I just pasted the patch into Thunderbird it would work, since
> it had
> no tabs.  But bizarrely, if I look at the patch in the mailer, it shows a
> two-space
> prefix, but when I save the email to a file, it has a three-space prefix.
> WTF?

Yea. Not many mailers can be trusted with sending patches. I'd
recommend git-send-email. :)

thanks
-john

Thread

[PATCH] clocksource_cyc2ns: avoid overflowing 64 bits Chris Metcalf <cmetcalf@mellanox.com> - 2016-11-16 18:00 +0100
  Re: [PATCH] clocksource_cyc2ns: avoid overflowing 64 bits John Stultz <john.stultz@linaro.org> - 2016-11-16 19:10 +0100
    Re: [PATCH] clocksource_cyc2ns: avoid overflowing 64 bits John Stultz <john.stultz@linaro.org> - 2016-11-16 20:50 +0100
      Re: [PATCH] clocksource_cyc2ns: avoid overflowing 64 bits John Stultz <john.stultz@linaro.org> - 2016-11-16 21:10 +0100
    Re: [PATCH] clocksource_cyc2ns: avoid overflowing 64 bits John Stultz <john.stultz@linaro.org> - 2016-11-16 20:50 +0100

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