On Fri, Jul 04, 2014 at 07:21:17AM -0700, Jarno Rajahalme wrote: > When a reference counted object is also RCU protected the deletion of > the object's memory is always postponed. This allows > memory_order_relaxed to be used also for unreferencing, as RCU > quiescing provides a full memory barrier (it has to, or otherwise > there could be lingering accesses to objects after they are recycled). > > Also, when access to the reference counted object is protected via a > mutex or a lock, the locking primitives provide the required memory > barrier functionality. > > Also, add ovs_refcount_try_ref_rcu(), which takes a reference only if > the refcount is non-zero and returns true if a reference was taken, > false otherwise. This can be used in combined RCU/refcount scenarios > where we have an RCU protected reference to an refcounted object, but > which may be unref'ed at any time. If ovs_refcount_try_ref_rcu() > fails, the object may still be safely used until the current thread > quiesces. > > Signed-off-by: Jarno Rajahalme <jrajaha...@nicira.com>
> +/* Increments 'refcount', but only if it is non-zero. > + * > + * This may only be called an object which is RCU protected during > + * this call. This implies that its possible desctruction is "destruction" > + * postponed until all current RCU threads quiesce. > + * > + * Returns false if the refcount was zero. In this case the object may > + * be safely accessed until the current thread quiesces, but no additional Acked-by: Ben Pfaff <b...@nicira.com> _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
