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    SubjectRe: [PATCH] a local-timer-free version of RCU
    On Sat, Nov 06, 2010 at 03:42:19PM -0400, Mathieu Desnoyers wrote:
    > * Mathieu Desnoyers (mathieu.desnoyers@efficios.com) wrote:
    > > > > +/**
    > > > > + * rcu_read_unlock - marks the end of an RCU read-side critical section.
    > > > > + * Check if a RCU batch was started while we were in the critical
    > > > > + * section. If so, call rcu_quiescent() join the rendezvous.
    > > > > + *
    > > > > + * See rcu_read_lock() for more information.
    > > > > + */
    > > > > +void __rcu_read_unlock(void)
    > > > > +{
    > > > > + struct rcu_data *r;
    > > > > + int cpu, flags;
    > > > > +
    > >
    > > Another memory barrier would be needed here to ensure that the memory accesses
    > > performed within the C.S. are not reordered wrt nest_count decrement.
    >
    > Nevermind. xchg() acts as a memory barrier, and nest_count is only ever touched
    > by the local CPU. No memory barrier needed here.

    You beat me to it. ;-)

    Thanx, Paul

    > Thanks,
    >
    > Mathieu
    >
    > >
    > > > > + cpu = smp_processor_id();
    > > > > + r = &per_cpu(rcu_data, cpu);
    > > > > + if (--r->nest_count == 0) {
    > > > > + flags = xchg(&r->flags, 0);
    > > > > + if (flags & DO_RCU_COMPLETION)
    > > > > + rcu_quiescent(cpu);
    > > > > + }
    > > > > +}
    > > > > +EXPORT_SYMBOL(__rcu_read_unlock);
    > >
    > > Thanks,
    > >
    > > Mathieu
    > >
    > > --
    > > Mathieu Desnoyers
    > > Operating System Efficiency R&D Consultant
    > > EfficiOS Inc.
    > > http://www.efficios.com
    >
    > --
    > Mathieu Desnoyers
    > Operating System Efficiency R&D Consultant
    > EfficiOS Inc.
    > http://www.efficios.com
    > --
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