Le 08/03/2024 à 14:14, Adrian Hunter a écrit :
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>
> Consolidate vdso_calc_delta(), in preparation for further simplification.
>
> Suggested-by: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
> ---
> arch/powerpc/include/asm/vdso/gettimeofday.h | 17 ++---------------
> arch/s390/include/asm/vdso/gettimeofday.h | 7 ++-----
> lib/vdso/gettimeofday.c | 4 ++++
> 3 files changed, 8 insertions(+), 20 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/vdso/gettimeofday.h b/arch/powerpc/include/asm/vdso/gettimeofday.h
> index f0a4cf01e85c..f4da8e18cdf3 100644
> --- a/arch/powerpc/include/asm/vdso/gettimeofday.h
> +++ b/arch/powerpc/include/asm/vdso/gettimeofday.h
> @@ -14,6 +14,8 @@
>
> #define VDSO_HAS_TIME 1
>
> +#define VDSO_DELTA_NOMASK 1
> +
> static __always_inline int do_syscall_2(const unsigned long _r0, const unsigned long _r3,
> const unsigned long _r4)
> {
> @@ -105,21 +107,6 @@ static inline bool vdso_clocksource_ok(const struct vdso_data *vd)
> }
> #define vdso_clocksource_ok vdso_clocksource_ok
>
> -/*
> - * powerpc specific delta calculation.
> - *
> - * This variant removes the masking of the subtraction because the
> - * clocksource mask of all VDSO capable clocksources on powerpc is U64_MAX
> - * which would result in a pointless operation. The compiler cannot
> - * optimize it away as the mask comes from the vdso data and is not compile
> - * time constant.
> - */
Please keep the comment. You can move it close to VDSO_DELTA_NOMASK
> -static __always_inline u64 vdso_calc_delta(u64 cycles, u64 last, u64 mask, u32 mult)
> -{
> - return (cycles - last) * mult;
> -}
> -#define vdso_calc_delta vdso_calc_delta
> -
> #ifndef __powerpc64__
> static __always_inline u64 vdso_shift_ns(u64 ns, unsigned long shift)
> {
> diff --git a/arch/s390/include/asm/vdso/gettimeofday.h b/arch/s390/include/asm/vdso/gettimeofday.h
> index db84942eb78f..7937765ccfa5 100644
> --- a/arch/s390/include/asm/vdso/gettimeofday.h
> +++ b/arch/s390/include/asm/vdso/gettimeofday.h
> @@ -6,16 +6,13 @@
>
> #define VDSO_HAS_CLOCK_GETRES 1
>
> +#define VDSO_DELTA_NOMASK 1
> +
> #include <asm/syscall.h>
> #include <asm/timex.h>
> #include <asm/unistd.h>
> #include <linux/compiler.h>
>
> -#define vdso_calc_delta __arch_vdso_calc_delta
> -static __always_inline u64 __arch_vdso_calc_delta(u64 cycles, u64 last, u64 mask, u32 mult)
> -{
> - return (cycles - last) * mult;
> -}
>
> static __always_inline const struct vdso_data *__arch_get_vdso_data(void)
> {
> diff --git a/lib/vdso/gettimeofday.c b/lib/vdso/gettimeofday.c
> index ce2f69552003..042b95e8164d 100644
> --- a/lib/vdso/gettimeofday.c
> +++ b/lib/vdso/gettimeofday.c
> @@ -13,7 +13,11 @@
> static __always_inline
> u64 vdso_calc_delta(u64 cycles, u64 last, u64 mask, u32 mult)
> {
> +#ifdef VDSO_DELTA_NOMASK
> + return (cycles - last) * mult;
> +#else
> return ((cycles - last) & mask) * mult;
> +#endif
See
https://docs.kernel.org/process/coding-style.html#conditional-compilation
You don't need #ifdefs here.
One solution is to define VDSO_DELTA_NOMASK to 0 in
include/vdso/datapage.h after including asm/vdso/gettimeofday.h :
#ifndef VDSO_DELTA_NOMASK
#define VDSO_DELTA_NOMASK 0
#endif
Then
u64 vdso_calc_delta(u64 cycles, u64 last, u64 mask, u32 mult)
{
if (VDSO_DELTA_NOMASK)
mask = ~0ULL;
return ((cycles - last) & mask) * mult;
}
or
u64 vdso_calc_delta(u64 cycles, u64 last, u64 mask, u32 mult)
{
if (VDSO_DELTA_NOMASK)
return (cycles - last) * mult;
return ((cycles - last) & mask) * mult;
}
> }
> #endif
>
> --
> 2.34.1
>