Re: [PATCH v6 01/19] kernel: Standardize vdso_datapage

Vincenzo Frascino
2019-06-10T11:07:51Z

Hi Huw,

On 10/06/2019 11:31, Huw Davies wrote:
> On Mon, Jun 10, 2019 at 11:17:48AM +0100, Vincenzo Frascino wrote:
>> On 10/06/2019 10:27, Huw Davies wrote:
>>> On Thu, May 30, 2019 at 03:15:13PM +0100, Vincenzo Frascino wrote:
>>>> --- /dev/null
>>>> +++ b/include/vdso/datapage.h
>>>> @@ -0,0 +1,91 @@
>>>> +/* SPDX-License-Identifier: GPL-2.0 */
>>>> +#ifndef __VDSO_DATAPAGE_H
>>>> +#define __VDSO_DATAPAGE_H
>>>> +
>>>> +#ifdef __KERNEL__
>>>> +
>>>> +#ifndef __ASSEMBLY__
>>>> +
>>>> +#include <linux/bits.h>
>>>> +#include <linux/time.h>
>>>> +#include <linux/types.h>
>>>> +
>>>> +#define VDSO_BASES (CLOCK_TAI + 1)
>>>> +#define VDSO_HRES (BIT(CLOCK_REALTIME) | \
>>>> + BIT(CLOCK_MONOTONIC) | \
>>>> + BIT(CLOCK_BOOTTIME) | \
>>>> + BIT(CLOCK_TAI))
>>>> +#define VDSO_COARSE (BIT(CLOCK_REALTIME_COARSE) | \
>>>> + BIT(CLOCK_MONOTONIC_COARSE))
>>>> +#define VDSO_RAW (BIT(CLOCK_MONOTONIC_RAW))
>>>> +
>>>> +#define CS_HRES_COARSE 0
>>>> +#define CS_RAW 1
>>>
>>> CS_HRES_COARSE seems like a confusing name choice to me. What you
>>> really mean is not RAW.
>>>
>>> How about CS_ADJ to indicate that its updated by adjtime?
>>> CS_XTIME might be another option.
>>>
>>
>> I divided the timers in 3 sets (HRES, COARSE, RAW), CS_HRES_COARSE refers to the
>> first two and CS_RAW to the third. I will ad a comment to explain the logic in
>> the next iteration.
>
> I'm thinking ahead about a possible CLOCK_MONOTONIC_RAW_COARSE (which
> would be useful at least for Wine). In that case you'd have four clock
> types non-raw and raw, each with either hres or coarse.
>

Thanks for this, I was not aware of CLOCK_MONOTONIC_RAW_COARSE.
I tried to find, though, some details, but I could not find any. Could you
please provide some reference?

> Huw.
>

--
Regards,
Vincenzo