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SubjectRe: [patch 11/11] x66/vdso: Add CLOCK_TAI support
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> On Sep 14, 2018, at 7:27 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
>
> On Fri, 14 Sep 2018, Andy Lutomirski wrote:
>>> On Sep 14, 2018, at 5:50 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
>>>
>>> With the storage array in place it's now trivial to support CLOCK_TAI in
>>> the vdso. Instead of extending the array to accomodate CLOCK_TAI, make use
>>> of the fact that:
>>>
>>> - CLOCK ids are set in stone
>>> - CLOCK_THREAD_CPUTIME is never going to be supported in the VDSO so
>>> the array slot 3 is unused
>>> - CLOCK_TAI is id 11 which results in 3 when masked with 0x3
>>>
>>> Add the mask to the basetime array lookup and set up the CLOCK_TAI base
>>> time in update_vsyscall().
>>
>> That’s... horrible. In an amazing way. Can you add BUILD_BUG_ON somewhere
>> to assert that this actually works?
>
> Sure, but changing any of the clock ids will cause more wreckage than that.
>

I’m more concerned that we add a new one and break the magic masking. Maybe two start sharing the same slot.

> Thanks,
>
> tglx

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