> > > >-----Original Message----- > > >From: Van Haaren, Harry > > >> > > > > /** > > >> > > > > * Add a key to an existing hash table. > > >> > > > >@@ -222,7 +222,7 @@ rte_hash_add_key(const struct rte_hash > > >> > > > >*h, const void > > >> > > *key); > > >> > > > > * array of user data. This value is unique for this key. > > >> > > > > */ > > >> > > > > int32_t > > >> > > > >-rte_hash_add_key_with_hash(const struct rte_hash *h, const > > >> > > > >void *key, > > >> > > hash_sig_t sig); > > >> > > > >+rte_hash_add_key_with_hash(struct rte_hash *h, const void > > >> > > > >+*key, > > >> > > hash_sig_t sig); > > >> > > > > > > >> > > > > / > > >> > > > > > >> > > > I think the above changes will break ABI by changing the > > >> > > > parameter > > >> type? > > >> > > Other people may know better on this. > > >> > > > > >> > > Just removing a const should not change the ABI, I believe, > > >> > > since the const is just advisory hint to the compiler. Actual > > >> > > parameter size and count remains unchanged so I don't believe there > is an issue. > > >> > > [ABI experts, please correct me if I'm wrong on this] > > >> > > > >> > > > >> > [Certainly no ABI expert, but...] > > >> > > > >> > I think this is an API break, not ABI break. > > >> > > > >> > Given application code as follows, it will fail to compile - even > > >> > though > > >> running > > >> > the new code as a .so wouldn't cause any issues (AFAIK). > > >> > > > >> > void do_hash_stuff(const struct rte_hash *h, ...) { > > >> > /* parameter passed in is const, but updated function > > >> > prototype is > > >> non- > > >> > const */ > > >> > rte_hash_add_key_with_hash(h, ...); } > > >> > > > >> > This means that we can't recompile apps against latest patch > > >> > without application code changes, if the app was passing a const > > >> > rte_hash struct > > >> as > > >> > the first parameter. > > >> > > > >> Agree. Do we need to do anything for this? > > > > > >I think we should try to avoid breaking API wherever possible. > > >If we must, then I suppose we could follow the ABI process of a > > >deprecation notice. > > > > > >From my reading of the versioning docs, it doesn't document this case: > > >https://doc.dpdk.org/guides/contributing/versioning.html > > > > > >I don't recall a similar situation in DPDK previously - so I suggest > > >you ask Tech board for input here. > > > > > >Hope that helps! -Harry > > [Wang, Yipeng] > > Honnappa, how about use a pointer to the counter in the rte_hash > > struct instead of the counter? Will this avoid API change? > I think it defeats the purpose of 'const' parameter to the API and provides > incorrect information to the user. Yipeng, I think I have misunderstood your comment. I believe you meant; we could allocate memory to the counter and store the pointer in the structure. Please correct me if I am wrong. This could be a solution, though it will be another cache line access. It might be ok given that it is a single cache line for entire hash table.
> IMO, DPDK should have guidelines on how to handle the API compatibility > breaks. I will send an email to tech board on this. > We can also solve this by having counters on the bucket. I was planning to do > this little bit later. I will look at the effort involved and may be do it > now.