On 7/19/17 1:02 AM, Jiri Pirko wrote: > From: Ido Schimmel <ido...@mellanox.com> > > Listeners of the FIB notification chain are expected to be able to take > and release a reference on notified IPv6 routes. This is needed in the > case of drivers capable of offloading these routes to a capable device. > > Since notifications are sent in an atomic context, these drivers need to > take a reference on the route, prepare a work item to offload the route > and release the reference at the end of the work. > > Currently, rt6i_ref is used to indicate in how many FIB nodes a route > appears. Different code paths rely on rt6i_ref being 0 to indicate the > route is no longer used by the FIB. > > For example, whenever a route is deleted or replaced, fib6_purge_rt() is > run to make sure the route is no longer present in intermediate nodes. A > BUG_ON() at the end of the function is executed in case the reference > count isn't 1, as it's only supposed to appear in the non-intermediate > node from which it's going to be deleted. > > Instead of changing the semantics of rt6i_ref, a new reference count is > added, so that external users could also take a reference on routes > without modifying rt6i_ref. > > To make sure external users don't release routes used by the FIB, the > reference count is set to 1 upon creation of a route and decremented by > the FIB upon rt6_release(). > > The reference count is atomic, as it's not protected by any locks and > placed in the 40 bytes hole after the existing rt6i_ref.
I'd rather not add another reference counter. Debugging reference leaks is a huge PITA now; adding another counter just makes it worse. Why can't the BUG_ON in fib6_purge_rt be removed since there are other reference holders now?
