Jakub Kicinski <jakub.kicin...@netronome.com> writes: > On Mon, 04 Mar 2019 23:28:14 +0100, Toke Høiland-Jørgensen wrote: >> Jakub Kicinski <jakub.kicin...@netronome.com> writes: >> > On Mon, 04 Mar 2019 20:05:30 +0100, Toke Høiland-Jørgensen wrote: >> >> > Hm. I think you'll still need a lock (mutex?) on the alloc path, but >> >> > the free path should be fine as long as you load the map pointer before >> >> > looking at the refcnt (atomic op ensuring the barrier there). >> >> >> >> Yeah, for the per-namespace refcnt it's pretty straight forward, the >> >> trouble is the global count that needs to iterate over all namespaces; >> >> probably need to put that all behind a (non-spin)lock, right? >> > >> > Because net iteration is under RCU? You can switch to taking net_rwsem >> > for that one, no? I'm probably confused again ;) >> >> Because there's a single refcount that needs to trigger >> creation/deletion of *all* the default maps. I.e. >> >> if (atomic_dec_return(&global_refcnt)) >> for_each_namespace(net) >> destroy_default_map(net); >> >> which needs to not step on the toes of a subsequent >> >> if (atomic_inc_return(&global_refcnt) == 1) >> for_each_namespace(net) >> create_default_map(net); >> >> (or vice versa, of course). >> >> Not sure there's a way to do that without wrapping both of those >> constructs (including the refcnt inc/dec) in a mutex? > > Seems like it :(
Right. Well I'm glad that we at least agree, so I can stop racking my brain for other ways to do it ;) -Toke
