Messages in this thread | | | Date | Thu, 15 Apr 2010 07:28:52 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH 01/13] powerpc: Add rcu_read_lock() to gup_fast() implementation |
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On Wed, Apr 14, 2010 at 03:51:50PM +0200, Peter Zijlstra wrote: > On Mon, 2010-04-12 at 20:43 -0700, Paul E. McKenney wrote: > > > So we might have to support the interrupt assumption, at least in some > > > form, with those guys... > > > > One way to make the interrupt assumption official is to use > > synchronize_sched() rather than synchronize_rcu(). > > Well, call_rcu_sched() then, because the current usage is to use > call_rcu() to free the page directories. > > Paul, here is a call_rcu_sched() available in kernel/rcutree.c, but am I > right in reading that code that that would not be available for > preemptible RCU?
Both call_rcu_sched() and call_rcu() are always there for you. ;-)
o If CONFIG_TREE_RCU (or CONFIG_TINY_RCU), they both have the same implementation.
o If CONFIG_TREE_PREEMPT_RCU, call_rcu_sched() is preemptible and call_rcu() is not.
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?
Thanx, Paul
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