Re: [PATCH RFC tip/core/rcu 3/4] rcu: Make RCU_FAST_NO_HZ accountfor pauses out of idle

[Peter Zijlstra]

On Thu, 2012-04-26 at 07:49 -0700, Paul E. McKenney wrote:
> >   per_cpu(rcu_dyntick.first_pass, cpu) = 0;

> I must confess that I had no idea that you could say the above.  I would
> have expected to have to say the following:
> 
>     per_cpu(rcu_dyntick, cpu).first_pass = 0; 

They both work and are afaik identical. The first takes the per-cpu
address of rcu_dyntick and adds the offset of first_pass, then
transforms the per-cpu address to a linear address. The second
transforms the per-cpu address of rcu_dyntick, transforms it to a linear
address and then adds the offset of first_pass, IOW:

 (&rcu_dyntick + offset) + per_cpu_offset == 
		(&rcu_dyntick + per_cpu_offset) + offset



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