linux-kernel - Re: [PATCH 01/19] vdso: Consolidate vdso_calc

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Date: Fri, 8 Mar 2024 18:09:27 -0800
From: John Stultz <jstultz@...gle.com>
To: Adrian Hunter <adrian.hunter@...el.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Michael Ellerman <mpe@...erman.id.au>, 
	Nicholas Piggin <npiggin@...il.com>, Christophe Leroy <christophe.leroy@...roup.eu>, 
	"Aneesh Kumar K.V" <aneesh.kumar@...nel.org>, "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>, 
	Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>, 
	Alexander Gordeev <agordeev@...ux.ibm.com>, Christian Borntraeger <borntraeger@...ux.ibm.com>, 
	Sven Schnelle <svens@...ux.ibm.com>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	"H. Peter Anvin" <hpa@...or.com>, Andy Lutomirski <luto@...nel.org>, 
	Vincenzo Frascino <vincenzo.frascino@....com>, Stephen Boyd <sboyd@...nel.org>, 
	Peter Zijlstra <peterz@...radead.org>, Randy Dunlap <rdunlap@...radead.org>, 
	Bjorn Helgaas <bhelgaas@...gle.com>, Arnd Bergmann <arnd@...db.de>, 
	Anna-Maria Behnsen <anna-maria@...utronix.de>, linuxppc-dev@...ts.ozlabs.org, 
	linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org
Subject: Re: [PATCH 01/19] vdso: Consolidate vdso_calc_delta()

On Fri, Mar 8, 2024 at 5:15 AM Adrian Hunter <adrian.hunter@...el.com> wrote:
>
> Consolidate vdso_calc_delta(), in preparation for further simplification.
>
> Suggested-by: Thomas Gleixner <tglx@...utronix.de>
> Signed-off-by: Adrian Hunter <adrian.hunter@...el.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(-)
>
> --- 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
>  }

Nit: Just for readability, usually we avoid #ifdefs inside of functions.

Instead maybe:
#ifdef VDSO_DELTA_NOMASK
static __always_inline
u64 vdso_calc_delta(u64 cycles, u64 last, u64 mask, u32 mult)
 {
       return (cycles - last) * mult;
 }
#else
static __always_inline
u64 vdso_calc_delta(u64 cycles, u64 last, u64 mask, u32 mult)
 {
      return ((cycles - last) & mask) * mult;
 }
#endif