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SubjectRe: [patch 14/15] lib/vdso: Avoid highres update if clocksource is not VDSO capable
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Le 14/01/2020 à 19:52, Thomas Gleixner a écrit :
> If the current clocksource is not VDSO capable there is no point in
> updating the high resolution parts of the VDSO data.
>
> Replace the architecture specific check with a check for a VDSO capable
> clocksource and skip the update if there is none.
>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> ---
> arch/arm/include/asm/vdso/vsyscall.h | 7 -------
> include/asm-generic/vdso/vsyscall.h | 7 -------
> kernel/time/vsyscall.c | 14 +++++++-------
> 3 files changed, 7 insertions(+), 21 deletions(-)
>
> --- a/arch/arm/include/asm/vdso/vsyscall.h
> +++ b/arch/arm/include/asm/vdso/vsyscall.h
> @@ -22,13 +22,6 @@ struct vdso_data *__arm_get_k_vdso_data(
> #define __arch_get_k_vdso_data __arm_get_k_vdso_data
>
> static __always_inline
> -bool __arm_update_vdso_data(void)
> -{
> - return cntvct_ok;
> -}
> -#define __arch_update_vdso_data __arm_update_vdso_data
> -
> -static __always_inline
> void __arm_sync_vdso_data(struct vdso_data *vdata)
> {
> flush_dcache_page(virt_to_page(vdata));
> --- a/include/asm-generic/vdso/vsyscall.h
> +++ b/include/asm-generic/vdso/vsyscall.h
> @@ -11,13 +11,6 @@ static __always_inline struct vdso_data
> }
> #endif /* __arch_get_k_vdso_data */
>
> -#ifndef __arch_update_vdso_data
> -static __always_inline bool __arch_update_vdso_data(void)
> -{
> - return true;
> -}
> -#endif /* __arch_update_vdso_data */
> -
> #ifndef __arch_update_vsyscall
> static __always_inline void __arch_update_vsyscall(struct vdso_data *vdata,
> struct timekeeper *tk)
> --- a/kernel/time/vsyscall.c
> +++ b/kernel/time/vsyscall.c
> @@ -71,15 +71,15 @@ void update_vsyscall(struct timekeeper *
> {
> struct vdso_data *vdata = __arch_get_k_vdso_data();
> struct vdso_timestamp *vdso_ts;
> + s32 clock_mode;
> u64 nsec;
> - s32 mode;

Can we name is clock_mode in patch 9 instead of changing name here ?

Christophe

>
> /* copy vsyscall data */
> vdso_write_begin(vdata);
>
> - mode = tk->tkr_mono.clock->vdso_clock_mode;
> - vdata[CS_HRES_COARSE].clock_mode = mode;
> - vdata[CS_RAW].clock_mode = mode;
> + clock_mode = tk->tkr_mono.clock->vdso_clock_mode;
> + vdata[CS_HRES_COARSE].clock_mode = clock_mode;
> + vdata[CS_RAW].clock_mode = clock_mode;
>
> /* CLOCK_REALTIME also required for time() */
> vdso_ts = &vdata[CS_HRES_COARSE].basetime[CLOCK_REALTIME];
> @@ -105,10 +105,10 @@ void update_vsyscall(struct timekeeper *
> WRITE_ONCE(vdata[CS_HRES_COARSE].hrtimer_res, hrtimer_resolution);
>
> /*
> - * Architectures can opt out of updating the high resolution part
> - * of the VDSO.
> + * If the current clocksource is not VDSO capable, then spare the
> + * update of the high reolution parts.
> */
> - if (__arch_update_vdso_data())
> + if (clock_mode != VDSO_CLOCKMODE_NONE)
> update_vdso_data(vdata, tk);
>
> __arch_update_vsyscall(vdata, tk);
>

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