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

Huw Davies
2019-06-10T10:32:01Z

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.

Huw.