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Message-ID: <02bcd954-5323-4663-a766-f53c67c5a18f@samsung.com>
Date: Tue, 8 Jul 2025 17:17:18 +0200
From: Marek Szyprowski <m.szyprowski@...sung.com>
To: Thomas Weißschuh <thomas.weissschuh@...utronix.de>,
Andy Lutomirski <luto@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
Vincenzo Frascino <vincenzo.frascino@....com>, Shuah Khan
<shuah@...nel.org>, Anna-Maria Behnsen <anna-maria@...utronix.de>, Frederic
Weisbecker <frederic@...nel.org>, John Stultz <jstultz@...gle.com>, Stephen
Boyd <sboyd@...nel.org>, Catalin Marinas <catalin.marinas@....com>, Will
Deacon <will@...nel.org>, Arnd Bergmann <arnd@...db.de>
Cc: linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-arch@...r.kernel.org, Richard
Cochran <richardcochran@...il.com>, Christopher Hall
<christopher.s.hall@...el.com>, Miroslav Lichvar <mlichvar@...hat.com>,
Werner Abt <werner.abt@...nberg-usa.com>, David Woodhouse
<dwmw2@...radead.org>, Kurt Kanzenbach <kurt@...utronix.de>, Nam Cao
<namcao@...utronix.de>, Antoine Tenart <atenart@...nel.org>
Subject: Re: [PATCH 06/14] vdso/gettimeofday: Return bool from
clock_gettime() helpers
On 01.07.2025 10:58, Thomas Weißschuh wrote:
> The internal helpers are effectively using boolean results,
> while pretending to use error numbers.
>
> Switch the return type to bool for more clarity.
>
> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
> ---
> lib/vdso/gettimeofday.c | 58 +++++++++++++++++++++++++------------------------
> 1 file changed, 30 insertions(+), 28 deletions(-)
This patch landed in today's linux-next as commit fcc8e46f768f
("vdso/gettimeofday: Return bool from clock_gettime() helpers"). In my
tests I found that it causes serious problem with hwclock operation on
some of my ARM 32bit test boards. I observe that calling "hwclock -w -f
/dev/rtc0" never ends on those boards. Disabling vdso support (by
removing ARM architected timer) fixes this issue.
> diff --git a/lib/vdso/gettimeofday.c b/lib/vdso/gettimeofday.c
> index 9b77f23566f6a35887d4c9aaefc61a971131b499..c5266532a097c06f33d12e345c695357d75abf42 100644
> --- a/lib/vdso/gettimeofday.c
> +++ b/lib/vdso/gettimeofday.c
> @@ -82,8 +82,8 @@ const struct vdso_time_data *__arch_get_vdso_u_timens_data(const struct vdso_tim
> #endif /* CONFIG_GENERIC_VDSO_DATA_STORE */
>
> static __always_inline
> -int do_hres_timens(const struct vdso_time_data *vdns, const struct vdso_clock *vcns,
> - clockid_t clk, struct __kernel_timespec *ts)
> +bool do_hres_timens(const struct vdso_time_data *vdns, const struct vdso_clock *vcns,
> + clockid_t clk, struct __kernel_timespec *ts)
> {
> const struct vdso_time_data *vd = __arch_get_vdso_u_timens_data(vdns);
> const struct timens_offset *offs = &vcns->offset[clk];
> @@ -103,11 +103,11 @@ int do_hres_timens(const struct vdso_time_data *vdns, const struct vdso_clock *v
> seq = vdso_read_begin(vc);
>
> if (unlikely(!vdso_clocksource_ok(vc)))
> - return -1;
> + return false;
>
> cycles = __arch_get_hw_counter(vc->clock_mode, vd);
> if (unlikely(!vdso_cycles_ok(cycles)))
> - return -1;
> + return false;
> ns = vdso_calc_ns(vc, cycles, vdso_ts->nsec);
> sec = vdso_ts->sec;
> } while (unlikely(vdso_read_retry(vc, seq)));
> @@ -123,7 +123,7 @@ int do_hres_timens(const struct vdso_time_data *vdns, const struct vdso_clock *v
> ts->tv_sec = sec + __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
> ts->tv_nsec = ns;
>
> - return 0;
> + return true;
> }
> #else
> static __always_inline
> @@ -133,16 +133,16 @@ const struct vdso_time_data *__arch_get_vdso_u_timens_data(const struct vdso_tim
> }
>
> static __always_inline
> -int do_hres_timens(const struct vdso_time_data *vdns, const struct vdso_clock *vcns,
> - clockid_t clk, struct __kernel_timespec *ts)
> +bool do_hres_timens(const struct vdso_time_data *vdns, const struct vdso_clock *vcns,
> + clockid_t clk, struct __kernel_timespec *ts)
> {
> - return -EINVAL;
> + return false;
> }
> #endif
>
> static __always_inline
> -int do_hres(const struct vdso_time_data *vd, const struct vdso_clock *vc,
> - clockid_t clk, struct __kernel_timespec *ts)
> +bool do_hres(const struct vdso_time_data *vd, const struct vdso_clock *vc,
> + clockid_t clk, struct __kernel_timespec *ts)
> {
> const struct vdso_timestamp *vdso_ts = &vc->basetime[clk];
> u64 cycles, sec, ns;
> @@ -150,7 +150,7 @@ int do_hres(const struct vdso_time_data *vd, const struct vdso_clock *vc,
>
> /* Allows to compile the high resolution parts out */
> if (!__arch_vdso_hres_capable())
> - return -1;
> + return false;
>
> do {
> /*
> @@ -173,11 +173,11 @@ int do_hres(const struct vdso_time_data *vd, const struct vdso_clock *vc,
> smp_rmb();
>
> if (unlikely(!vdso_clocksource_ok(vc)))
> - return -1;
> + return false;
>
> cycles = __arch_get_hw_counter(vc->clock_mode, vd);
> if (unlikely(!vdso_cycles_ok(cycles)))
> - return -1;
> + return false;
> ns = vdso_calc_ns(vc, cycles, vdso_ts->nsec);
> sec = vdso_ts->sec;
> } while (unlikely(vdso_read_retry(vc, seq)));
> @@ -189,13 +189,13 @@ int do_hres(const struct vdso_time_data *vd, const struct vdso_clock *vc,
> ts->tv_sec = sec + __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
> ts->tv_nsec = ns;
>
> - return 0;
> + return true;
> }
>
> #ifdef CONFIG_TIME_NS
> static __always_inline
> -int do_coarse_timens(const struct vdso_time_data *vdns, const struct vdso_clock *vcns,
> - clockid_t clk, struct __kernel_timespec *ts)
> +bool do_coarse_timens(const struct vdso_time_data *vdns, const struct vdso_clock *vcns,
> + clockid_t clk, struct __kernel_timespec *ts)
> {
> const struct vdso_time_data *vd = __arch_get_vdso_u_timens_data(vdns);
> const struct timens_offset *offs = &vcns->offset[clk];
> @@ -223,20 +223,20 @@ int do_coarse_timens(const struct vdso_time_data *vdns, const struct vdso_clock
> */
> ts->tv_sec = sec + __iter_div_u64_rem(nsec, NSEC_PER_SEC, &nsec);
> ts->tv_nsec = nsec;
> - return 0;
> + return true;
> }
> #else
> static __always_inline
> -int do_coarse_timens(const struct vdso_time_data *vdns, const struct vdso_clock *vcns,
> - clockid_t clk, struct __kernel_timespec *ts)
> +bool do_coarse_timens(const struct vdso_time_data *vdns, const struct vdso_clock *vcns,
> + clockid_t clk, struct __kernel_timespec *ts)
> {
> - return -1;
> + return false;
> }
> #endif
>
> static __always_inline
> -int do_coarse(const struct vdso_time_data *vd, const struct vdso_clock *vc,
> - clockid_t clk, struct __kernel_timespec *ts)
> +bool do_coarse(const struct vdso_time_data *vd, const struct vdso_clock *vc,
> + clockid_t clk, struct __kernel_timespec *ts)
> {
> const struct vdso_timestamp *vdso_ts = &vc->basetime[clk];
> u32 seq;
> @@ -258,10 +258,10 @@ int do_coarse(const struct vdso_time_data *vd, const struct vdso_clock *vc,
> ts->tv_nsec = vdso_ts->nsec;
> } while (unlikely(vdso_read_retry(vc, seq)));
>
> - return 0;
> + return true;
> }
>
> -static __always_inline int
> +static __always_inline bool
> __cvdso_clock_gettime_common(const struct vdso_time_data *vd, clockid_t clock,
> struct __kernel_timespec *ts)
> {
> @@ -270,7 +270,7 @@ __cvdso_clock_gettime_common(const struct vdso_time_data *vd, clockid_t clock,
>
> /* Check for negative values or invalid clocks */
> if (unlikely((u32) clock >= MAX_CLOCKS))
> - return -1;
> + return false;
>
> /*
> * Convert the clockid to a bitmask and use it to check which
> @@ -284,7 +284,7 @@ __cvdso_clock_gettime_common(const struct vdso_time_data *vd, clockid_t clock,
> else if (msk & VDSO_RAW)
> vc = &vc[CS_RAW];
> else
> - return -1;
> + return false;
>
> return do_hres(vd, vc, clock, ts);
> }
> @@ -293,9 +293,11 @@ static __maybe_unused int
> __cvdso_clock_gettime_data(const struct vdso_time_data *vd, clockid_t clock,
> struct __kernel_timespec *ts)
> {
> - int ret = __cvdso_clock_gettime_common(vd, clock, ts);
> + bool ok;
>
> - if (unlikely(ret))
> + ok = __cvdso_clock_gettime_common(vd, clock, ts);
> +
> + if (unlikely(!ok))
> return clock_gettime_fallback(clock, ts);
> return 0;
> }
>
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
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