Re: [Xen-devel] [PATCH] xen: RTDS: fix another instance of the 'read NOW()' race

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Tue, May 24, 2016 at 05:06:58PM +0200, Dario Faggioli wrote:
> which was overlooked in 779511f4bf5ae ("sched: avoid
> races on time values read from NOW()").
> 
> Reported-by: Jan Beulich <jbeulich@xxxxxxxx>
> Signed-off-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>

Release-acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>

> ---
> Cc: Meng Xu <mengxu@xxxxxxxxxxxxx>
> Cc: George Dunlap <george.dunlap@xxxxxxxxxx>
> Cc: Jan Beulich <JBeulich@xxxxxxxx>
> Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
> ---
>  xen/common/sched_rt.c |    4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/xen/common/sched_rt.c b/xen/common/sched_rt.c
> index 0946101..5b077d7 100644
> --- a/xen/common/sched_rt.c
> +++ b/xen/common/sched_rt.c
> @@ -840,12 +840,14 @@ static void
>  rt_vcpu_insert(const struct scheduler *ops, struct vcpu *vc)
>  {
>      struct rt_vcpu *svc = rt_vcpu(vc);
> -    s_time_t now = NOW();
> +    s_time_t now;
>      spinlock_t *lock;
>  
>      BUG_ON( is_idle_vcpu(vc) );
>  
>      lock = vcpu_schedule_lock_irq(vc);
> +
> +    now = NOW();
>      if ( now >= svc->cur_deadline )
>          rt_update_deadline(now, svc);
>  
> 

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