From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <bruce.richardson@intel.com>
Received: from mga11.intel.com (mga11.intel.com [192.55.52.93])
 by dpdk.org (Postfix) with ESMTP id 7E07D3990
 for <dev@dpdk.org>; Fri, 25 Mar 2016 11:45:41 +0100 (CET)
Received: from orsmga003.jf.intel.com ([10.7.209.27])
 by fmsmga102.fm.intel.com with ESMTP; 25 Mar 2016 03:45:40 -0700
X-ExtLoop1: 1
X-IronPort-AV: E=Sophos;i="5.24,390,1455004800"; d="scan'208";a="771270606"
Received: from bricha3-mobl3.ger.corp.intel.com ([10.237.220.58])
 by orsmga003.jf.intel.com with SMTP; 25 Mar 2016 03:45:38 -0700
Received: by  (sSMTP sendmail emulation); Fri, 25 Mar 2016 10:45:38 +0025
Date: Fri, 25 Mar 2016 10:45:37 +0000
From: Bruce Richardson <bruce.richardson@intel.com>
To: Olivier Matz <olivier.matz@6wind.com>
Cc: dev@dpdk.org
Message-ID: <20160325104537.GA18028@bricha3-MOBL3>
References: <1458044745-32764-1-git-send-email-olivier.matz@6wind.com>
 <56F513CF.4090604@6wind.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <56F513CF.4090604@6wind.com>
Organization: Intel Shannon Ltd.
User-Agent: Mutt/1.5.23 (2014-03-12)
Subject: Re: [dpdk-dev] [RFC] hash/lpm: return NULL if the object exists
X-BeenThere: dev@dpdk.org
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: patches and discussions about DPDK <dev.dpdk.org>
List-Unsubscribe: <http://dpdk.org/ml/options/dev>,
 <mailto:dev-request@dpdk.org?subject=unsubscribe>
List-Archive: <http://dpdk.org/ml/archives/dev/>
List-Post: <mailto:dev@dpdk.org>
List-Help: <mailto:dev-request@dpdk.org?subject=help>
List-Subscribe: <http://dpdk.org/ml/listinfo/dev>,
 <mailto:dev-request@dpdk.org?subject=subscribe>
X-List-Received-Date: Fri, 25 Mar 2016 10:45:41 -0000

On Fri, Mar 25, 2016 at 11:32:47AM +0100, Olivier Matz wrote:
> 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
Hi Olivier,

the idea looks good, since an object already existing is an error condition on
create. One small change to the libs I'd suggest is to set rte_errno to 
EEXIST before exit, so that the error reason is known to the app.

Regards,
/Bruce