Messages in this thread | | | Date | Fri, 16 Apr 2010 06:43:36 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH 01/13] powerpc: Add rcu_read_lock() to gup_fast() implementation |
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On Fri, Apr 16, 2010 at 04:54:51PM +1000, Benjamin Herrenschmidt wrote: > On Thu, 2010-04-15 at 07:28 -0700, Paul E. McKenney wrote: > > > > Of course, with call_rcu_sched(), the corresponding RCU read-side > > critical > > sections are non-preemptible. Therefore, in CONFIG_PREEMPT_RT, these > > read-side critical sections must use raw spinlocks. > > > > Can the code in question accommodate these restrictions? > > What we protect against is always code that hard-disable IRQs (though > there seem to be a bug in the hugepages code there...). Would that > work ?
From the perspective of call_rcu_sched() and synchronize_sched(), the following things mark RCU-sched read-side critical sections:
1. rcu_read_lock_sched() and rcu_read_unlock_sched().
2. preempt_disable() and preempt_enable(), along with anything else that disables preemption.
3. local_bh_disable() and local_bh_enable(), along with anything else that disables bottom halves.
4. local_irq_disable() and local_irq_enable(), along wiht anything else that disables hardirqs.
5. Handlers for NMIs.
So I believe that in this case call_rcu_sched() is your friend. ;-)
Thanx, Paul
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