On Tue, Oct 06, 2015 at 10:27:41PM +0200, Peter Zijlstra wrote:
> On Tue, Oct 06, 2015 at 09:13:45AM -0700, Paul E. McKenney wrote:
> > /**
> > + * rcu_pointer_handoff() - Hand off a pointer from RCU to other mechanism
> > + * @p: The pointer to hand off
> > + *
> > + * This is simply an identity function, but it documents where a pointer
> > + * is handed off from RCU to some other synchronization mechanism, for
> > + * example, reference counting or locking. In C11, it would map to
> > + * kill_dependency(). It could be used as follows:
> > + *
> > + * rcu_read_lock();
> > + * p = rcu_dereference(gp);
> > + * long_lived = is_long_lived(p);
> > + * if (long_lived) {
> > + * if (!atomic_inc_not_zero(p->refcnt))
> > + * long_lived = false;
> > + * else
> > + * p = rcu_pointer_handoff(p);
> > + * }
> > + * rcu_read_unlock();
> > + */
> > +#define rcu_pointer_handoff(p) (p)
>
> Will you actually be using this? It seems a tad pointless to add if you
> don't.
Some of the LLVM guys believe that they can diagnose RCU pointer leaks
if this is used. But yes, it does need to be used.
Thanx, Paul
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