Re: [RFC] hash/lpm: return NULL if the object exists

[Olivier Matz <olivier.matz@6wind.com>]

Hi Bruce,

On 03/15/2016 01:25 PM, Olivier Matz wrote:
> Seen by trying to fix the func_reentrancy autotest. The test
> was doing the following on several cores in parallel:
> 
>   name = "common_name";
>   do several times {
>       obj = allocate_an_object(name)   // obj = ring, mempool, hash, lpm, ...
>       if (obj == NULL && lookup(name) == NULL)
>           return TEST_FAIL;
>   }
> 
> Issues:
> 
> 1/ rings, mempools, hashs API are not coherent
>    rings and mempool return NULL if the object does not exist
>    hash and lpm return an object that was allocated allocated if
>    it already was allocated
> 
> 2/ The hash/lpm API looks dangerous: when an object is returned,
>    the user does not know if it should be freed or not (no refcnt)
> 
> 3/ There are some possible race conditions in cuckoo_hash as the
>    lock is not held in rte_hash_create(). We could find some cases
>    where NULL is returned when the object already exists (ex: when
>    rte_ring_create() fails).
> 
> This patch tries to rationalize the APIs of lpm and hash.
> 
> Signed-off-by: Olivier Matz <olivier.matz@6wind.com>

Sorry, I forgot to CC you in the first mail. Do you have any opinion
about this rfc patch?

Thanks,
Olivier