Date: Tue, 09 Jun 2015 13:32:26 +0200 From: Sebastian Huber <sebastian.huber@embedded-brains.de> To: Konstantin Belousov <kostikbel@gmail.com> Cc: freebsd-hackers@freebsd.org, phk@phk.freebsd.dk Subject: Re: [PATCH v3] timecounters: Fix timehand generation read/write Message-ID: <5576CECA.7070109@embedded-brains.de> In-Reply-To: <20150609112837.GL2499@kib.kiev.ua> References: <1433331966-27548-1-git-send-email-sebastian.huber@embedded-brains.de> <1433838715-22850-1-git-send-email-sebastian.huber@embedded-brains.de> <20150609105526.GK2499@kib.kiev.ua> <5576C90A.9010807@embedded-brains.de> <20150609112837.GL2499@kib.kiev.ua>
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On 09/06/15 13:28, Konstantin Belousov wrote:
> On Tue, Jun 09, 2015 at 01:07:54PM +0200, Sebastian Huber wrote:
>> You still need the compiler memory barriers in the UP case (at least
>> with GCC 4.9 on PowerPC), e.g. something like this:
> Fair.
>
> diff --git a/sys/kern/kern_tc.c b/sys/kern/kern_tc.c
> index 9dca0e8..01c61bd 100644
> --- a/sys/kern/kern_tc.c
> +++ b/sys/kern/kern_tc.c
> @@ -189,6 +190,33 @@ tc_delta(struct timehands *th)
> tc->tc_counter_mask);
> }
> =20
> +static u_int
> +tc_getgen(struct timehands *th)
> +{
> +
> +#ifdef SMP
> + return (atomic_load_acq_int(&th->th_generation));
> +#else
> + u_int gen;
> +
> + gen =3D th->th_generation;
> + __compiler_membar();
> + return (gen);
> +#endif
> +}
> +
> +static void
> +tc_setgen(struct timehands *th, u_int newgen)
> +{
> +
> +#ifdef SMP
> + atomic_store_rel_int(&th->th_generation, newgen);
> +#else
> + __compiler_membar();
> + th->th_generation =3D newgen;
> +#endif
> +}
> +
> /*
> * Functions for reading the time. We have to loop until we are sure=
that
> * the timehands that we operated on was not updated under our feet. =
See
Thanks, this looks good to me.
--=20
Sebastian Huber, embedded brains GmbH
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Phone : +49 89 189 47 41-16
Fax : +49 89 189 47 41-09
E-Mail : sebastian.huber@embedded-brains.de
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