linux-kernel - Re: [PATCH 06/14] vdso/gettimeofday: Return bool from clock

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Message-ID: <20250709092958-37148883-ed89-40fe-8cd5-ded5dd60957e@linutronix.de>
Date: Wed, 9 Jul 2025 09:34:25 +0200
From: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
To: Marek Szyprowski <m.szyprowski@...sung.com>, 
	Thomas Gleixner <tglx@...utronix.de>
Cc: Andy Lutomirski <luto@...nel.org>, 
	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>, 
	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

Hi Marek,

On Tue, Jul 08, 2025 at 05:49:18PM +0200, Marek Szyprowski wrote:
> On 08.07.2025 17:17, Marek Szyprowski wrote:
> > 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.
> 
> I spent some time analyzing the code refactored in this patch and it 
> looks that the following change is missing:

Thanks for the report and investigation!

> diff --git a/lib/vdso/gettimeofday.c b/lib/vdso/gettimeofday.c
> index c5266532a097..7e79b02839b0 100644
> --- a/lib/vdso/gettimeofday.c
> +++ b/lib/vdso/gettimeofday.c
> @@ -344,7 +344,7 @@ __cvdso_gettimeofday_data(const struct 
> vdso_time_data *vd,
>          if (likely(tv != NULL)) {
>                  struct __kernel_timespec ts;
> 
> -               if (do_hres(vd, &vc[CS_HRES_COARSE], CLOCK_REALTIME, &ts))
> +               if (!do_hres(vd, &vc[CS_HRES_COARSE], CLOCK_REALTIME, &ts))
>                          return gettimeofday_fallback(tv, tz);
> 
>                  tv->tv_sec = ts.tv_sec;
> 
> 
> In my tests this fixed the hwclock issue on the mentioned boards.

This fix looks correct to me.


tglx:

Are you going to fold the fix into the commit or do you want a proper patch?


Marek:

If a new patch is required, do you want to send it? You found and fixed the
issue after all. If not, I'll take care of it.


Thomas