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SubjectRe: [PATCH] fix vsyscall settimeofday
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On Mon, 2007-03-05 at 08:56 -0800, Daniel Walker wrote:
> I've only seen this on x86_64 .
>
> The vsyscall state only gets updated when a timer interrupts comes in . So
> if the time is set long before the next timer, there will be a period when
> a gettimeofday() won't reflect the correct time.
>
> I added an explicit update_vsyscall() during the settimeofday(), that way
> the vsyscall state doesn't get stale.
>
> Any thought John?

Oh! Yes, very good catch, Daniel!

Thanks so much!
-john


> Signed-Off-By: Daniel Walker <dwalker@mvista.com>

Acked-by: John Stultz <johnstul@us.ibm.com>


> ---
> kernel/timer.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> Index: linux-2.6.20/kernel/timer.c
> ===================================================================
> --- linux-2.6.20.orig/kernel/timer.c
> +++ linux-2.6.20/kernel/timer.c
> @@ -861,6 +861,8 @@ int do_settimeofday(struct timespec *tv)
> clock->error = 0;
> ntp_clear();
>
> + update_vsyscall(&xtime, clock);
> +
> write_sequnlock_irqrestore(&xtime_lock, flags);
>
> /* signal hrtimers about time change */

-
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