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From: David Miller <davem@davemloft.net>
Subject: Re: [PATCH] net: disable preemption before call smp_processor_id()
Date: Sat, 07 Aug 2010 22:25:43 -0700 (PDT)
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From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Date: Sat, 7 Aug 2010 21:57:51 -0700

> If I cover preemptible RCU's semantics, a first cut comes out like this:
> 
>  * In non-preemptible RCU implementations (TREE_RCU and TINY_RCU), it
>  * is illegal to block while in an RCU read-side critical section.  In
>  * preemptible RCU implementations (TREE_PREEMPT_RCU and TINY_PREEMPT_RCU)
>  * in CONFIG_PREEMPT kernel builds, RCU read-side critical sections may
>  * be preempted, but explicit blocking is illegal.  Finally, in preemptible
>  * RCU implementations in real-time (CONFIG_PREEMPT_RT) kernel builds,
>  * RCU read-side critical sections may be preempted and they may also
>  * block, but only when acquiring spinlocks that are subject to priority
>  * inheritance.
> 
> Does that seem reasonable?

Sounds good to me.