Re: [PATCH] configure HAVE_UNSTABLE_SCHED_CLOCK for SGI_SN systems

Greg KH
2009-01-15T18:48:32Z

On Tue, Jan 06, 2009 at 10:27:41AM -0600, Dimitri Sivanich wrote:
> Turn on CONFIG_HAVE_UNSTABLE_SCHED_CLOCK for SGI_SN.
>
> SGI Altix has unsynchronized itc clocks. This results in rq->clock
> occasionally being set to a time in the past by a remote cpu.
>
> Note that it is possible that this problem may exist for other ia64
> machines as well, based on the following comment for sched_clock() in
> arch/ia64/kernel/head.S:
>
> * Return a CPU-local timestamp in nano-seconds. This timestamp is
> * NOT synchronized across CPUs its return value must never be
> * compared against the values returned on another CPU. The usage in
> * kernel/sched.c ensures that.
>
>
> Signed-off-by: Dimitri Sivanich <sivanich@sgi.com>
>
> ---
>
> Greg, if everyone is OK with this patch, this should also be applied
> to all stable trees starting with 2.6.26.

What is the status of this going into Linus's tree?

thanks,

greg k-h